A HISTORY OFELECTRICITY AND MAGNETISM

Burndy LibraryPublication No. 27

A HISTORY O FELECTRKITY AND MAGNETISM

Herbert W. Meyer

Foreword by Berri Dibnrr

~vEL~~~vENT Ec~N~MIQUEE-T eTUOE DES MARCHtS

; CEjW?E DE DOWMEWATIOrJ

RURNDY LIBRARYNonvalk, Connecticut

1972

.._

This book was designedby The MIT Press Design Department .I t was set in IBM Composer Bodoni

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or by any information storage and retrieval system,without permission in writing from the publisher.

ISBN 0 262 13070 X (hardcover)Library of Congress catalog tard number:

70-137473

FOREWORD BY BERN DIBNER xi

PREFACE xv1

EARLY DISCOVERIES 1Archcology and Paleontology; Magnetitç and the Lodestone; Thalesof Miletus; Ancient and Medieval Records, The Magnetic Compas;William Gilbert.

2

ELECTRICAL MACHINES AND EXPERIMENTSWITH STATIC ELECTRICITY 11

Otto van Guericke; Other Expçriments Wi th Stalic Electr ici ty;Stephen Gray and the Transmission of Electricity; Du Fay’s Experi-ment8 and His Discovery of Two Kinds of Electricity; Improvcmentsin Electrical Machines; The Leyde” Jar; The Spced of Electricity; SirWi l l i am Watson’s ‘Theories; MisceIlaneous Discoveries; BenjaminFranklin’s Experiments; Atmospheric Electr ici ty; Experiments inEurope with Atmospheric Electricity; Electrical Induction, Electro-scopes; Other Discoveries in the Eigbteenth Century

3VOLTAIC ELECTRICITY, ELECTROCHEMISTRY,

AND ELECTROMAGNETISM 34Galvanïs Frog Expcriments; Volta and the Voltaic Pile; Evolutionof the Battery and Discoveries with Electric Currents; Electromag-netism; Ampère; Ardgo, B io t and Savart; Faraday’8 Rotrting Con-ductor and Magnet and Barlow’s Wheel; Sturgeon’s Electromapnet,Galvanometers; Ampèrès and Ohm’s Laws.

4FARADAY AND HENRY 52

Faraday’s Formative Years; Faraday Appointed to the Royal I&i-tution; Electromagnetic Induction; Other Contributions by Faraday;Joseph Henry; Henry’s Firs t Excurs ions into Science; Henry Pro-poses tbe Electromagnetic Telegraph; Electromqnetic Induct ion;Self-Induction; Marriage and Professorship at Princeton; ElectricalOsci l la t ions and Electromagnetic Waves; Other Researches; TheSmithsonian Institution.

vi Contents

5DIRECT-CURRENT DYNAMOS AND MOTORS 71

Pixii’s Machine; Nollet’s Machines; Dynamos; Electric Motors.

6IMPROVEMENTS IN BATTERIES

AND ELECTROSTATIC MACHINES 77The Daniel1 Cell; The Grove Cell; the Leclanché Cell; Other Bat-teries; Storage Batteries; Electrostatic Induction Machines.

7ELECTRICAL INSTRUMENTS, LAWS, AND

DEFINITIONS OF UNITS 85Tangent Galvanometer; D’Arsonval Galvanometer; WheatstoneBridge; Electrical and Magnetic Laws; Electrical and Magnetic Units.

8THE ELECTRIC TELEGRAPH 95

Early Electromagnetic Telegraphs; Samuel F. B. Morse; Demonstra-tion of the First Morse Telegraph; Partnership with Alfred Vail; US.Government Interested in Telegraph; Demonstrations of the Im-proved Morse Telegraph; Patent Applications; Submarine Cable;Congress Appropriates $30,000 for an Experimental Line; Construc-tion of the Line; “What Hath God Wrought!“; Commercial Opera-tion of the Telegraph; Construction of New Telegraph Lines; West-ern Union; Printing Telegraphs; Relays; Duplex and MultiplexSystems; Railway Telegraphs; The First Transcontinental TelegraphLine; Electrical Manufacturing.

9THE ATLANTIC CABLE 115

Early Submarine Cables; Newfoundland Cable; The Atlantic Cable;Gable Company 1s Organized; Contracts for the Manufacture ofCable; The Cable Fleet; Loading and Testing the Cable; Laying theCable; Project Postponed until the Following Year; Second Attempt;Cable 1s Spliced in Mid-Ocean; Insulation Breaks Down; The SecondCable; Most of the Cable 1s Laid Successfully Before It Breaks; TheThird Cable; The Siphon Recorder.

Contents vii

10THE TELEPHONE 131

Bourscul and Rcis; Alexander Graham Bell; The Bell Family Movesto Canada; Classes in Boston; The Harmonie Telegraph; Boston Uni-versity and George Sanda; Thomas A. Watson; The Phonautagraphand thc Reis Tclcphone; Meeting with Joseph Henry; Agrecmentwith Sanda and Hubbard; Bell’8 Great Discovery; Despair: NewQwtcrs; Tclcphone Patent Granted; Thc Telcphonc at thc Ccnten-niai Exposition; Tcsting thc Telephone; Western Union Refuses toBuy thc Telephone; Bell 1s Manied; Organization of TelephoncCompanies; Infringement by the Western Union Telegraph Com-pany; BclI Patent Upheld; Transmitters; Theodore N. Vail: Evolu-tion of the BclI Companies; The Dial Tclephone; Bell Laboratoriesand Western Elcctric Company; Othcr Tclcphonc Systems.

11

ELECTRIC LIGHTING 152Arc Lampa; Arc Lamp Meehanisms; Carbons; Manufacturers; StrcetLiihting; Encloscd Are Lamps; Flaming Arcs; Incandescent ElcctricLights; Edison’s Incandescent Lamp; Edison Electric Light Com-pany; Menlo Park; The Scarch for Bcttcr Filament Mat&&; Im-provements in Lamp Se.& and in Dynamos; First Commercial Instal-latiow Pearl Street, the First Central Station for IncandescentLigbting; Schencctady Works; Forcign Incandescent Liiht Installa-tions; Improved Lamps; Othcr Types of Lampe.; Metal FilamentLamps; Tube Lighting; Fluorescent Lamps; Lamp Efficiencies;Special-Purpose Lamps.

12ALTERNATING CURRENTS 177

Thc Transformer; Induction C~ils; Gaulard and Gibbs: WestinghouseAItcrnating-Currcnt Systcm; Altcrnating-Curent Gcnerators; Fre-qucncics; AC-DC Conversion; Alternating-Curent Motors; NiagaraFalls Development; Transmission Lines; Frequency and VoltageStandards.

13ELECTRIC TRACTION 190

Public Transportation; Rails and Railways; Streçt Railways; ElectricPropulsion; EIeetrification of Street Railways; Thc Carbon Bru&;

vi i i Contents

Rapid Conversion from Horsecars to Electric Propulsion; Suburbanand Main Line Electrification; The Decline of Electric Street Rail-ways .

14ELECTROMAGNETIC WAVES, RADIO,FACSIMILE, AND TELEVISION 198

A Century of Progress; Hertz Discovers Electromagnetic Waves; Sig-naling without Wires; Guglielmo Marconi; First Radio Patent;Tuned Circuits; Continuous Waves; Detectors; The Edison Effect;The Fleming Valve; De Forest Audion; Amplification; Armstrong’sOscillator Tube; The Alexanderson High-Frequency Generator;Amateur Radio and Radio Broadcasting; Regulation of Radio; Fed-eral Communications Commission; Frequency Allocations; RadioReceivers; Facsimile Transmission; Commercial Facsimile; Photo-electric Devices; Pictures by Cable; Television; The Scanning Diskand Mechanical Television; The Iconoscope; Improvements on theIconoscope; Transmission by Radio Waves; Regulation of Televisionand Channel Allocations.

15THE CROOKES TUBE,XRAYS,

RADIOACTIVITY, STRUCTURE OF THE ATOM,ACCELERATORS AND ATOMIC RESEARCH 224

The Crookes Tube; Vacuum Tubes before Crookes; Sir WilliamCrookes and His Experiments; Later Developments in CathodeRays; X Rays; Radioactivity; Scattering of Electrons; PhotoelectricEffect; Planck’s Constant; Photoelectrons and Einstein’s Equation;Hydrogen Spectra; Structure of the Atom; Heavier Atoms, EllipticalOrbits, and Spin; Theoretical and Experimental Physics of the1920s; Other Subatomic Particles; The Electron Microscope; Radia-tion Detectors; Accelerators and Atomic Research.

16MICROWAVES, RADAR, RADIO RELAY,COAXIAL CABLE, COMPUTERS 253

Microwaves; Radar; Early British Developments and Installations;American Wartime Research and Development; New Oscillators andOther Tubes; Types of Radar; Other Uses of Radar; TelephoneRadio Relay; Frequency Band Allocations; Coaxial Cable; Com-

Conlents i x

puters; Computer Development; Digital and Analog Computer~;Electronic Computers; Memory Systems; Input and Output Syotems; Numeration.

17PLASMAS, MASERS,

LASERS, FUEL CELLS,PIEZOELECTRIC CRYSTALS, TRANSISTORS 275

Plasmas; Masers and Lasers; Cas Lasers; Applications; Electrolytieand Electrochemical Phenomena; Piezoelectricity; S&d State De-vices; Semiconductors; Transistors; The Transistor Industry.

18ATOMIC ENERGY, GOVERNMENT RESEARCH,

NUCLEAR FUSION 289Atomic Energy; Nuelear Rescarch for the United States Gavern-ment; Los Alamos Laboratory and the Atomic Bomb; AtomicEnergy Commission;Nuclear Power Plants; Nuclear Fusion; Whither.

BIBLIOGRAPHY 299INDEX 307

FOREWORD

Of the many ages of mari-the Stone Age, the tlronïe Age,the Iran Age, etc.-that preceded the 18008, and that ledone into the other, none was as rewarding to mankind as theelectrical age. We now stand in awe of the space age, andinfear we face the nuclear age. From electricity, however, hasb e e n drawn a n ever growing abundance o f light, power,warmth, intelligence, and medical aid-ail beneficent, silent,and ready

Electricity is the one force in the arsenal of man thatfound no precedent in carlier history, nor was it drawnfrorn classical times. It is fully the fruit of the Enlighten-ment, in timc and place, and it generated its own enlighten-ment by extending man’s waking hours and making himmaster of his own dawn and night. With no more than thetouch of his finger he cari summon energy ahnost withoutlimit and cari as readily cancel his summons. He cari controlbis environment, he cooled when he wishes it or be warmedwhen needed. HC cari, in an instant, speak to anyone in anylocation where the fine filaments that carry this new forcebave been extended. Ile ca”, at Will, observe and lista topublic figures presenting problems of state or be enter-tained by whatever his choice of talent might be. No czar oremperor could command more.

With this new force mari has probed the universe aroundhim and has been compelled to change his estimates of itssize exponentially. With radio astronomy he has penetrateddistances measured in billions of light-years. He bas probedthe elemental nature of matter and energy; his geniuschallenged by their complexity, he devised new electronicprobes and analytical instruments. His networks of com-puters bave e x t e n d e d h i s intellectual powers ( i f n o t

xi i Forcword

his wisdom) beyond a11 philosophie dreams. His weaponsof destruction are diffused in hundreds of locationsin the ground, in the sea, and in the air, each weapon’sdestructive strength measured in the equivalent megatonsof explosive and a11 controlled by electrical energy equiva-lent to the power of a flea, the signal traveling over a hotline.

With such knowledge, such power, such control of envi-ronment, and su& fleet means of communication, man hasdemonstrated his ability to reach the moon, travel its harshsurface, and return to earth-recording and televising hisposition, observations, and thoughts during the entire jour-ney. This, and more, was realized in only a little more thana decade from the decision to attempt such a difficult mis-sion.

Admittedly, the acquisition of electricity as an instrumentof power and control in the inventory of man’s abilities wasno small addition. One cari therefore stop and inquire aboutthe circumstances that brought this acquisition about andreview the events and personalities whose labors revealedthe characteristics of a force unknown throughout the ear-lier millenia of work and study.

Two events ushered in the interest that blossomed into thearcane realm of electricity and magnetism. The first was thepublication in London of a book on electricity and magne-tism written by the physician to Queen Elizabeth who haddevoted his leisure time and much of his fortune to investi-gating the properties of magnets and electrified bodies.Dr. William Gilbert’s book, De Magnete, was published inLatin in 1600; its strength lay in the thoroughness withwhich the author examined each claim made in earlier writ-ings on electrical phenomena, magnets, and compasses andin the exhaustive experimentation that separated the undis-

Porewurd xiii

puted results of his observations from the accumulated

superstitious clairns of the past. This launched the scienceof electriçity and magnetism Gem a firm bais of perfor-

mance derived from objective experimentation.

The second event of significance that pushed electricityou its way toward usefulness was an announcement made in1800 by Alessaudro Volta that a new forrn of electricity

could be drawn from a pile of altemating zinc and silverdisks stacked oue on the other, eaçh pair separated fromthc adjoining pair by a cloth or papa disk saturated in

brine. From the ends of this pile, Volta could draw a con-tinuously flowing electric current, which he and others

soon uscd 10 decompose water, to cause charcoal to glow

with intense light in au electric arc, and, later, to depositmet& by electrolysis.

These two events-Gilhert’s book on magnetisrn (1600)and Volta’s constant-current clectric cell (1800)-represent

two çenturies that neatly bracketcd the naseent phase ofelectrical development. ‘I‘he one formulated m o r e accurate

kuowledge about a force thcn useful for navigation in anera of voyaging and exploration; thc other çhanged the con-

cept of electric generation from frictional clectricity, giving

off bigger and bigger sparks, into an eleçtric source of vastpotential. However, the period must not be closed without

tribute being paid to Franklin, an intrepid experimenter,who ideutified lightning as electricity and with his lightning

rod helpcd rescue mankind from the terrer of destroyed

homes, steeples, and other structures. At the same time hehelped guide man’s faith to the trurr character of natural

forces sud away from the ancient superstitions about light-ning and the gods’ intentions.Tbe next important step on the ranrp of electrical progress

was Lhe discovery by Oersted in 1820 that a wire connect-

xiv Foreword

ing the ends of a voltaic pile was enveloped by a magneticfield. It was then found that if such a wire were looped intoa coi1 the magnetic strength was greatly intensified. Withsuch a magnetic field Faraday showed, in 1831, that amoving electrical conductor had an electric current inducedin it; the electric generator and its important adjunct, thetransformer, were thus born. The generator supplied elec-trie current in abundance and with this and auxiliary cur-rent from electric batteries the electric telegraph devel-oped-the first important instantaneous disseminator ofhuman intelligence over long distances. There followedthe laying of the first transatlantic table, the telephone, theelectric lamp, and the electric motor. Each developmentgenerated a family of by-products-electroplating, the elec-trie tramway, the moving picture-and each created a cor-responding major industry.

As the drama of electrical development unfolds, we relateeach forward step to the genius and perseverance of someexperimenter, some inventor, some innovator. TO himshould go a11 the honor of a grateful people, for these arethe true heroes of the modern world. The pages that followWill unfold their story, their struggles and attainments. Maythe telling never end.

Bern Dibner

PREFACE

PURPOSE OF BOOKIt is the purpose OC this book to attempt to give to thereader, who bas arrived upon the wortd scene in the midstof a scientific explosion, a sense of perspective and direc-tion. The word explosion as it is used here is not entiretyaccurate because it implies a sudden, violent, and instanta-mous event. Ttre burgeoning of science resembtes morenearly the propagation of a new grain Crom a few seeds, to afew bushets, and finatly to a tremendous harvest.

A history such as tbis might be presented as a collection ofbiographies or as a series of stories concerning inventionsand discoveries. It could discuss tbc unfotding of eventsfrom the standpoint of pure science or it might be weightedon the side of technotogy. Att of these considerations baveplayed a part in tbe writing of this story. Hopefutty thebook has blended these differing viewpoints in such a wayas to stimutate the interest, not onty of the student ofscience, but atso that of the casuat reader, who finds him-self surrounded by the fruits of science and technotogy,knowing not from whence they came.

EXPERIMENTAL AND THEORETICAL RESEARCHDuring t h e earty period o f t h e devetopment o f etectricaland magnetic science, beginning witb William Gilbert andOtto van Guericke, discoveries were the resutt of experi-ment coupted with observation and interpretation. Atabout the same time tbere began a different kind of scien-tific exploration based targety on mathematics, exemptifiedby Kepter’s planetary taws and Newton’s laws of motion. Inetectricat sc ience mathematical analysis based on expeti-

x v i Preface

ment came a little later in the work of such men as Ampère,Coulomb, Biot and Savart, Gauss, Weber, and Ohm.

Maxwell, an ardent admirer of Faraday’s great genius, in-terpreted Faraday’s discoveries mathematically and contrib-uted his own mathematical findings, but credit for some ofMaxwell’s discoveries must be shared with Helmholtz,whose versatility in science has rarely been equaled. AfterMaxwell and Helmholtz followed a period of twenty ormore years of fruitful experimentation. As a result ofthe Michelson-Morley experiment, Lorentz and Einsteinbrought forth new concepts of length and time that seri-ously upset the Newtonian system. Under the new theorylength and time were no longer absolutes but were relative,and Newton’s laws were valid only as special cases. Evenmore upsetting was the suggestion that matter and energywere convertible, one into the other.

These great triumphs of theoretical science were only abeginning, and there was much more to corne. The natureof matter and energy became the primary abject of physicalresearch with most astonishing results. This type of researchbegan with the work of J. J. Thomson, Planck, Lenard,Moseley, Rutherford, and Bohr, followed a few years laterby the astonishing revelations of A. H. Compton, C. T. R.Wilson, de Broglie, Schrodinger, Heisenberg, Pauli, Born,Dirac, Davisson, Germer, G. P. Thomson, and Kikuchi.

MERGING OF THE PHYSICAL SCIENCESAs the nature of matter and its relationship to energy be-came clearer, the gaps between the branches of physicalscience began to close, and the lines of demarcation becameindistinct. It is therefore difficult in a work such as this toavoid being drawn into byways only remotely connectedwith the subject matter.

xvii Prefaee

ACKNOWLEDGMENTS

The author wishes to express his appreciation for the en-couragement and suggestions given by Dr. R. J. Collins,head of the Department of Electrical Engineering of theUniversity of Minnesota, and especially for important helpgiven by Dr. W. F. Brown, professor of Electrical Engineer-ing, also at the üniversity of Minnesota. 1 also owe a debtof gratitude ta my wife, Elfriede, for ber wluable assis-tance.

1

Early Discoveries

AKCHAEOLOGY AND PALEONTOLOGY

R e ç o r d e d political h i s t o r y now reaches back t o about

4000 R . C . , b u t we havc somc knowledge o f mankind o fmuch earher periods based on the findings of archaeologists

and paleontologists, aided by the studies of anthropologists.

P r e h i s t o r i c mari fashioned weapons, ta&, uiensils: a n dclothing from stone, shells, bone, wood, skins, and sinews.

Later he learned to use met&, such as copper and gold,

which were foond in their native state and required nosmelting. Bronze, which is usually an alloy of çopper and

tin. carne into use in Europe by the year 2000 B.C., or

perhaps earlier, and gave rise to the period known as the

Bronze Age.

There is no reliable record as to the date when the smelt-ing of the ores of copper, t in, lead, and zinc began, but

these met& were definitely in use before the beginning ofthe Christian Era. The Romans mined copper or copper

ores in Cyprus and later obtained tin from Gxnwall inEngland.

I t is difficult to determine the date of the earliest ironimplements, but iron artifacts bave been iound in Egypt

dating back to 4000 B.C. Iran in its native state occurs onlyin meteorites and in t iny needles sometimes found in ba-salta. Litt le is known as to the date when mari f irst pro-duced iron from ores, but there is evidence that by 1350

B.C. the Hittites in Asia Miner succeeded in reducing theoxides of iron.

MAGNETITE AND TIfE LODESTONE

There are probably few natural rnaterials known today that

were not also known to prehistoric mari, although he had

2 Chapter One

little knowledge of their uses. Among the rather widespreadand fairly abundant minerals of the earth is a very usefulore of iron called magnetite, which has the compositionFes04. It is a crystalline minera& very dark in color, havinga metallic luster, and a specific gravity equal to about five-sevenths of that of iron. Unlike any of the other iron ores itis magnetic, and this property gives it its name. There areoccasional pieces of magnetite, as found in nature, whichare permanently magnetized, and such pieces are known asloadstones or lodestones. In some specimens the magnetismis sufficiently strong to enable them to lift several timestheir weight of iron from one pole. There is good reason tobelieve that the attractive powers of lodestone had beenobserved as much as 3000 years before the Christian Era,but the directive properties of freely suspended pieces wereprobably not known until much later.We are told that Huang-ti, or Hwang-ti, or Hoang-ti, an

emperor of China in the year 2637 B.C., had a chariot uponwhich was mounted the figure of a woman, pivoted or sus-pended SO that it was free to turn in any direction. Theoutstretched arm of the statue pointed always to the southunder the influence of concealed lodestones.

Similar magnetic cars are mentioned by Chinese historiansat various times down to the early centuries of the ChristianEra. The Chinese also discovered that steel needles could bepermanently magnetized by the lodestone and used as com-passes. According to Humboldt, Tcheou-Koung, Chineseminister of state in 1110 B.C., used a compass employing asteel needle, and the same authority relates that Chinesemariners with the aid of compasses navigated the IndianOcean, in the third Century A.D.

Unlike the ancient civilizations of the West which per-ished, the Chinese civilization has continued in an almost

unbroken line down-to the present time, SO that its recordedhistory is fa more comptete than that of Babyton or Egypt.‘There is some disagreemerrt among sçhotars as to whether

or not the stories conccrning thc use of magnetic chariotso r magnetic needtes, b y t h e Chinese, i s façt o r f i c t i o n .Sinçe, however, such devices are possible, and since such

stories recur from time to time in Chinese history and leg-end, there seems ta be little rcason to rcject them.

THALES OF MILETUS

In 600 H.C . Greek çivilization and commerce were flouri&

ing. On the Grecian peninsula the City-states of Athens andSparta hûd grown ta greatuess and power. Nurnerous Greekcolonies had beerl planted on tbe shores of the Mediter-

ranean and Aegean seas, amorrg whicb was Ionia i n Asia

Miner. Miletus was a thriving seaport in lonia, in and out ofwhich sailed ships from all of the ports of the Mediter-

ranean. Its inhabitants, througb their trade with other coun-

tries, became well-ta-do and acquired much of the cultureo f olher civilizations o f the Mediterranean basin. Philos-

ophy, astronomy, mathcmatics, poetry, and art were culti-

vated atong with commerce.One of thc inhabitants of Miletus in the year 600 B.C. n-as

the philosopher Thales (64OL546 B.C.). A contemporaryof Draco, Soton, and of King Nebuchadnezzar of Babylon,

he was the founder of the Io&n school of philosophy from

which Socrates c a m e . Thales traveled extensively and re-ceiwd an important part of his çducation from the priestsat Memphis and Thebes in EQpt. Froln them he learned a

great deal about thc physical sciences and geometry, andinthe latter he S<><>I~ exceI I e d bis tcachers. Thales’s l i f e was

devoted to teaching, discussion, philosophy, and statecraft.

Ilnforturlately for posterity hc left no writings, and all that

4 Chapter One

we know of him was transmitted orally until Aristotle re-corded his teachings.

Thales is important in electrical history because he was thefirst person who is said to have observed the electrical prop-erties of amber. He noted that when amber was rubbed itacquired the ability to pick up light abjects, such as straw,dry grass, and the like. He also experimented with the lode-stone and knew of its power to attract iron. He apparentlyassociated the two phenomena, although more than twenty-four hundred years elapsed before any actual relationshipwas proved. We do not know whether Thales discoveredthese facts for himself or learned of them from the Egyp-tian priests or from others. He apparently did not know ofthe directive power of the lodestone.

It is from the Greek that our terms electricity and magne-tism are derived; the Greek word for amber is EXEKT~OU

(elektron), and the word magnet is thought to have cornefrom Magnesia, a district in Thessaly, in which lodestoneswere found. According to Pliny, however, the word is de-rived from Magnes, the name of a shepherd who observedthat the iron on the end of his crook was attracted bycertain stones on Mount Ida that proved to be lodestones.

ANCIENT AND MEDIEVAL RECORDS AFTER THALES

The earliest written record that mentions the electrical prop-erties of amber came from Theophrastus (about 300 B.C.).

Later, various other Greek and Roman writers alluded bothto the electrical properties of amber and the magnetic prop-erties of the lodestone. Pliny the elder (23-79 A.D.), aRoman naturalist whose untimely death occurred on theseashore at Retina not far from Pompeii, in the eruption ofMount Vesuvius, referred to the attractive powers ofamber several times in his Natural History. He wrote that

the Etruscans, about 600 B.C., were ablc to draw lightningfrom the clouds and to turn it aside. We learn from othersthat the Temple of Solomon may bave been protected fromlightning hy nurnerous Sharp points of metal that coveredthe roof and that were connected by means of pipes toçaverns in a hill. The temple of Juno is said to bave beensimilarly protected. Lucretius, the poet and author of DeRerum Natura, noted the ability of the lodestone to attractseveral iron rings, onc adhering to the other, and marveledat the peculiar behavior of iron filings in a brass bowl whena magnet was moved ahout heneath,it.

As the gxat Roman Empire declined, the culture ofGreece and Rome gradually vanished; Learning almost dis-appeared and for centuries was confined largely to themonks and prie& ib the Christian çhurch. After the rise ofIslam, in the early part of the seventh Century, there was agreat upsurge in learning among t h e Arab peoples, who ,even though they destroyed the library at Alexandria, trans-lated the works of the great pagan philosophas. Arab cul-ture flourished during the Dark Ages when Western learningwas at low ebb, where it remained until the beginning ofthe Renaissance.

There is an interesting item from Chinese history during

the early part of our era. Koupho (295-324 A.D.), a dis-tinguished Chinese naturalist, compared the a t t r a c t i v epower of the magnet with the ability of excited amber toattract mustard seeds. From his mariner of writing, it ap-pears that this property of amber was no new discovq,but it is tbe first time the phenomenon was mentioned inChinese history.

During the Middle Ages the properties of amber and thelodestone were not forgotten, but no new knowledge wasadded. St. Augustine in 426 A.D. expressed wonder at the

6 Chapter One

ability of the lodestone to hold several iron rings suspendedfrom it, and he mentioned an experiment in which a bit ofiron laid on a silver plate is made to follow the movementsof a magnet beneath the plate.

That long and dismal period of European history, gener-ally called the Dark Ages, or the Middle Ages, came to anend sometime during the thirteenth or fourteenth centuries.In the world of science there may be some disagreement asto who was the first real scientist in the revival of learning,but surely Albertus Magnus (1206?-1280) was among theearliest. He taught at the University of Paris, where he was adistinguished professor of theology and philosophy and wasalso among the most learned in the science of the day. Alsoat the University of Paris at the same time was Roger Bacon(1214?-1294), who had first studied at Oxford. He becamewell versed in the scientific works of the Greek philoso-phers and the Arab scholars. It was Roger Bacon, more thananyone of his time, who insisted that human progress de-pended upon research and scientific education. His re-searches carried him into the fields of alchemy, medicine,optics, and mathematics. He is sometimes credited with theinvention of the telescope and of gunpowder, although theformer is generally ascribed to Lippershey of Middleburg,Holland and the latter to Berthold Schwartz.

In Roger Bacon’s greatest work, his Opus Mujus (1268), hereversed the manner of thinking of the Greek philosophers,which was largely subjective, to reasoning based on experi-ment. His writings and experiments, however, got him intotrouble with the Church and he was accused of practicingblack magie. He had become a Franciscan monk upon hisreturn to England in 1250 but was soon enjoined by hisorder from writing or teaching and thereupon returned toParis, where later the ban was lifted by a new pope.

THE MAGNETIC COhtPASSOne of Koger BacOn’s teachers was Petrus Peregrinus, orPierre de Maricourt, who had carricd on numerous experi-nxmls i n rnagnetism. Petrus P e r e g r i n u s M-as net only ateachcr but also a soldier attached LO ~he engineer corps ofthe Frencb army. During thc year 1269, while he wa withthe armies of Charles of Anjou, which were besiegingLucera in southern Italy: he wrote a lengthy lelkr from biscamp to a friend named Sigerus de Foucancour~, at his oldhome in Picardy. ‘Thc letter described in detail bis experi-ments with magnetü, lhe construction of a floating com-pas, and also a pivoted compas employing a steel ncedlc.This compas was provided with a tard net unlike the mari-ner’s compass of today. An excellent translation of Pere-griuus’s Ieller has been made by Professor Silvanus P.Thompson.

T h e Italian historian Flavius Blondus writcs that Italianrnariners, sailing out of the harbor at Amalfi, used a floatingmagnet as a compas before 1269. Its invention was attrib-uted to a fiçtitions person named Flavio Gioia of Amalfi.Therr is an inconsistençy, however, in this account becausethe alleged invention oçcurred in 1302. Blondus asserts thatthe real origirr of the magnetic compass is unknown. Thereseems to be litlle doubt that thr Italiaos learned about lbecompas from the Arabs.

The magnetic compas wâs the first device having practicalvalue that came from experiments with magnetism. Afterthe tirne of Petrus Peregrinus the compas soon carne intogeneral use and led to many theories as tu the rasons forits behavior. Its variations in diffcrcnl longitudes werenoted, togçther with other changes of short duration. IJn-doubtedly the voyages of Columbus and Vasço da Gamawere greatly aided by its use.

8 Chapter One

With the invention or rediscovery of the compass came agreatly increased interest in magnetism. Many believed thatmagnetism was a cure for various diseases, and othersclaimed to be able to use compass needles, separated bygreat distances, as a means of telegraphic communication.Still others, among whom was Petrus Peregrinus, claimed tohave made perpetual motion machines using magnets.Robert Norman of Wapping, England, a maker of compassneedles, was the first to make a dipping needle. He foundthe inclination of the needle at London to be 71 degrees,50 minutes.

During the Renaissance epoch human progress was morerapid than at any earlier period. It was far more than arebirth of the classical learning of Greece and Rome. Notonly did art and literature flourish, but great new landswere discovered; printing, gunpowder, and the telescopewere invented; and Copernicus gave the world a new con-cept of the universe. The Church was shaken, and auto-cratic government began to lose its despotic power. Therewas, however, little further progress in the science of elec-tricity and magnetism until about the year 1600.

WILLIAM GILBERTWilliam Gilbert was born at Colchester in England in 1544.He studied medicine at St. John% College, Cambridge. Aftergraduation he traveled about Europe for a time and re-turned to London in 1573, where he practiced medicinevery successfully. At the same time he carried forward aseries of experiments in electricity and magnetism and alsostudied a11 of the available writings of others on the subject.Gilbert devoted seventeen years of his life to compiling theresults of his researches into a Latin volume entitled DeMagnete, Magneticisque Corporibus, et de Magno Magnete

Figure 1.1 William Gilbert Demonstrates Electrostatic Attractionat the Court of Queen Elizabeth (Courtesy Burndy Library)

Tellure;Physiologia Noua, Pluribus et Argumentes et Expr-imentis Lkmonstrata. This formidable title is now generallycondensed into De Magnete. It was published in 1600 andrepresented tbe greatest forward step in the study of elec-tricity and magnetism up to that time. Gilbert regarded theearth as a huge magnet and explained the behavior of thecompass on this bais. From his experiments in magnetismGilbert deduced many ideas concerning the magnetic field,magnetic induction, polarity, and tbe effects of tempera-turc on magnets. I n h i s electrical researches, he found along list of materials that could be electrified, which becalled electrics. He devised a form of electroscope that he

10 Chapter One

called a versorium, which was a pivoted nonmagneticneedle. He was the first to use the term electricity.

Gilbert’s ski11 as a physician and his genius as a scientistwere recognized by Queen Elizabeth, who appointed him asher court physician in 1601. He died in 1603.

Gilbert has been honored by the use of his name as theunit of magnetomotive force. In his De Magnete, Gilbertreiterated the plea of Roger Bacon for more intensive re-search. By a queer coincidence another Bacon, this timeSir Francis Bacon, who followed soon after Gilbert, pub-lished in 1620 a great work of science entitled Nouum Or-ganum. As far as we know, Sir Francis Bacon never carriedon any original scientific research, but he set forth the sci-entific achievements up to his time SO clearly and presentedthe case for research SO eloquently that the book was, andstill is, a source of inspiration for scientists.

I 2

Electrical Machinesand Experiments with

Static Electricity

Sçientific progress during thc later years of thç sixteenth

and throughout the seventeentb Century was astonishing.Among the great names of science of that period were Co-

pernicus, Gilbert, Brahc, Napier, Francis Bacon, Galileo,Kepler, Descartes, van Gueriçke. Torriçelli, Hoyle, Iluygens,

Mariotte, R’ewton, and Leibniz. During this period Aso, the

first experiments on the steam engine wcre made byde Caus, Papi”, and Savery. These experiments were carried

to suçcessful conclusions in the eighteenth Century by New-comen and Watt.

It is only fitting that in this recital of grcat men of science,

special mention be made of Sir Isaac Newton, who is re-garded by many as thc greatest of scient&. His contribu-t ions to human knowledge were largely in the fields of

rnathematics, optics, astronomy, and in tbe laws of mechan-

ics and gravitation. HC made sornc miner experiments inelectricity also, but his importance in this history lies prin-cipally in the effeçt of his work on research. His Principin

was the third great scientific work published in England inthe seventeenth century.

OTTO VON GIJERICKEIn electriçnl science there was again a considcrable lapse of

time alter Gilbert’s De Magnete until O t to van Gueriçke,the burgomaster of Magdeburg, constructed the f irst elec-

trical machine in 1660. Von Guericke is also distinguishedas the invcntor of the air pomp and as the one who deviscd

the spectaçuhw Magdeburg hemispheres experiment.

12 C h a p t e r Two

F@ure 2.1 Von Guericke’s Electrical Machine (From BumdyLibrary)

Von Guericke’s electrical machine marked the most sub-stantial advance yet made in electrical knowledge. In thismachine a sulfur bal1 that had been cast in a glass globe wasmounted on a shaft which passed through its tenter. Thebal1 was rotated by means of a crank at the end of theshaft. In later models the shaft was driven at higher speedby means of a belt that passed over a larger driving wheeland over a smaller pulley on the shaft carrying the sulfurbah. The rotating bal1 was excited by friction through theapplication of the dry hands or a cloth.

This machine produced far greater quantities of electricitythan had hitherto been available and made possible new andinteresting experiments. Von Guericke noted the attraction

and repulsion of feathers, the crackling noises and sparks,and the odor that pernreated the air when the machine wasexcited. He found also that the electrification of the bal1produced a tingling sensation when any part of the bodyapproached it. There is reason to believe that van Guerickenoted that electricity from his machine could be trans-mitted several feet over a piece of string. These experimentswere witnessed by many persons with lively interest, andnews of the device soon spread to all parts of Europe.

Within a short time similar machines with variations andimprovements were constructed by others. Sir Isaac New-ton became interested in the experiments and is creditedwith the construction of an electrical machine hsving a glassglobe about the year 1675.

OT"ER EXPERIMENTS WITH STATIC ELECTRICITYJean Picard, a French sstronomer, noted in 1675 that whena Torricellian barometer was agitated in thc dark, flashes oflight appeared in the evacuated space above the merçq.The mercury barometer was invented by Evangelista Ton%celli of Italy in 1643. It consisted of a vertical glass tubeclosed at one end and filled with mercury. When the mer-cury-filled tube was inverted with the open end below thesurface of the mercury in a cup, the level of the rnercury inthe tube dropped to a point at which it was sustained byatmospheric pressure, leaving a vacuum in the tube abovethe mercury. Francis Hawksbee pondered this phenomenonand in 1705 carried on a series of experiments to determinethe cause of this light. He used glass vessels containingmercury, some of whicb had been exhausted while othershad net. Wben the vessels were shaken, the light appearedin the evacuated vessels but only faintly in those containingair. Thc appearancc of tbe light was also different in the

14 Chapter Two

exhausted vessels from that in the vessels containing air. Inthe vacuum the light was in the nature of a glow that per-meated the evacuated space, whereas in the vessels con-taining air the light appeared as weak flashes.

Hawksbee discovered that similar effects could be pro-duced on glass vessels,without mercury simply by rubbingthe exterior surfaces, and thereby proved the electrical na-ture of the phenomenon. He also showed that an evacuatedglass globe could be made to glow by bringing it near an-other globe that had been electrified by rubbing. He per-formed many beautiful experiments showing colors andstriations with varying degrees of evacuation and variousshapes of glass vessels. He may have noted the similaritybetween these effects and the aurora borealis. Followingthese experiments, Hawksbee proceeded to build electricalmachines using revolving glass globes. Some of his machineswere powerful and produced sparks of considerable inten-sity.

Among other experimenters was Professor Johann Hein-rich Winckler of the University of Leipzig who, about theyear 1733, substituted a fixed cushion for the hand orcloths which had previously been used as rubbers. GeorgMatthias Boze (1710-1761) of Wittenberg about 1745added a prime conductor, with which greater quantities ofelectricity could be collected. At Erfurt a Scottish monknamed Gordon constructed a machine using a glass cylinderrather than the previously common glass globe.

About the year 1670, Robert Boyle, whose chief famerests on his work with gases, made some additions to Gil-bert’s list of substances that could be electrified and alsofound that the attractions between electrified and nonelec-trified bodies were mutual. In the Philosophical Transac-tions in 1708, Dr. William Wall published his observations

on the sparks and crackling noises emanating frorn electri-fied bodies, which he compared with lightning and thunder.Winckler made similar observations sornewhat later, andsuggested the use o f conductors f o r p r o t e c t i o n againstlightning.

STEPHEN GRAY ANI) 'THE TRANSMISSIOXOF ELECTRICITY

Stephen Gray (16Y5-1736), a pensioner at Charter Housein London, some time prior to 1728 began a series of elcc-trical experiments with very lirnited equipment. His carlierexperiments were of a miner nature, which included thedisçovery of the electrification by warming and rubhing ofsuch materials a s f e a t h c r s , hair, silk, linen, wool, cloth,paper, leather, wood, parchrncnt, and goldheaters skin. Ilefound also that lincn and papa could he made to give offlight in the dark.

His most notable discovery, however, was that electricitycould be transmitted. In 172Y he had made many fruitlessefforts to electrify met& by the same methods he had uscdon other materials when it occurred to him that perhaps hecould transfer a charge frorrr an electrified glass tube to apiece of metal. He used for this purpose a glass tuhel’/~ inches in diarneter and 3 feet, 5 incbes long. A Cork hadbeen fitted into each end of the tube to keep out the dust.He tried first ta determine whether or net there was anyappreciable difference in the electrification of the tube withand without the corks and found none. He did find, how-ever, that when the tuhe was electrified the Cork wouldattract and repel a feather.

In his next experiment he attached an ivory bal1 to theend of a fir stick about four inches long and inserted theother end of the stick in the Cork. When the tube was

16 Chapter Two

rubbed, he found that the bal1 was electrified as the corkhad been. Carrying the experiment further, he attached thebal1 to longer sticks and to brass and iron rods, with similarresults.

As the sticks and metal rods became longer, he experi-enced difficulty due to bending, and he conceived the ideaof using a piece of packthread or string attached to the corkand to the ivory ball. With the longest packthread he couldmanage by suspending the bal1 over the edge of a balconyhe was still able to transmit electrical charges to the ball. Hethen tried suspending a longer packthread over a nail in abeam to the ivory ball, but this time the experiment failed.He surmised correctly that the charge had been led offthrough the nail into the beam.

On June 30, 1729, Gray visited Granville Wheeler in thecountry to demonstrate his experiments. Together theyworked to transmit the electrical charges over the greatestpossible distance. Mr. Wheeler suggested suspending thepackthread on silk threads, and this arrangement workedadmirably. They had transmitted the charge over 80 feet ofpackthread. In order to increase the distance still further,they looped the packthread back through the same gallery,a total distance of 147 feet. In further experiments theyfinally reached a distance of 765 feet. In still other experi-ments they discovered that hair, rosin, and glass made suit-able supports for their packthread line. On the same day,which was July 2, 1729, Gray and Wheeler electrified largersurfaces such as a map and a tablecloth.

In August of the same year, Gray found that he couldproduce charges at the end of an insulated packthread linemerely by bringing the electrified glass tube near the otherend of the line without touching it and that the electrifica-tion was greatest at the far end of the line.

Gray made another notable discovery in which he foundthat an iron rod, pointed at both ends and suspended fromsilk lines, gave off cones of light in the dark when it wasapproached by an electrified glass tube. He also commentedon the similarity between electrical sparks with the noisesthey produced and flashes of lightning with peals of thun-der. No better example of the value of rescarch and obser-vation may be found than in Gray’s experiments with sim-ple apparatus and an inquiring mind.

Gray made the important discovery in 1729 that somesubstances were conductors and others were nonconduc-tors. He may bave been the first to use wires as conductors.The art of wiredrawing was not discovered until the four-teenth Century and did not reach England until thc seven-teentb century, SO that in the time of Gray, wire was still acomparatively new item.

DU FAY'S EXPERIMENTS AND 141s DISCOVERYOF TWO KINDS OF ELECTRICITY

In Paris Charles Du Fay (169%I73Y), a retired militaryofficer and a member of the French Academy of Sciences,reported the results of his experirnents to tbe Academyduring the years 1733 and 1734. HC disproved the state-ment by Jean Desaguliers that all bodies could be classifiedas electrics or nonelectrics by showing that ail bodies couldbe electrified. In the case of conductors it was necessarythat they be insulated. IIe showed that a string was a betterconductor when it was wet and succeeded in conduçtingelectricity over such a line a distance of 1256 feet. Amonghis other interesting experiments was the electrification ofthe human body when il was insulated from the ground. Henoted that when another person approached the one whowas electrified, he experienced a prickling sensation, and in

18 Chapter Two

a dark room there was an emission of sparks. Du Fayred iscovered an effect which had been observed byvon Guericke, namely, that a charged body attracts anotherbody, which after contact receives a similar charge and isthen repelled.

Du Fay’s most important discovery, however, was thatthere were two kinds of electricity, which he called vitreousand resinous. The first, he said, was produced on glass, rockcrystal, precious stones; hair of animais, and wool. Thesecond was produced on amber, copal, gum-lac, thread, andpaper. He announced also that these electricities repel simi-lar charges and attract opposite kinds.

IMPROVEMENTS IN ELECTRICAL MACHINES

In 1746 Dr. Ingenhousz made a glass plate machine, but thesame invention has also been attributed to Jesse Ramsden,although this was not until 1768. Benjamin Wilson about1746 invented a collecter for an electrical machine some-what resembling a comb. It consisted of a metallic rod witha number of fine points, SO mounted that the points wereclose to the revolving electrified surface.

THE LEYDEN JAR

A very important discovery was made on November 4,1745 by E. G. von Kleist of Kammin, Pomerania, Germany,which was first credited to Professor Pieter van Musschen-broek and his assistant Cunaeus of Leyden, Holland, butpriority belongs to von Kleist. Nevertheless, the inventionhas since been known as the Leyden jar. It was found that abottle partly filled with water and containing a metal rodwhich projected through the neck would, when held in thehand and the rod presented to an electrical machine, receive

a powerful charge. SO great was the charge that after thebottle was removed from the electrical machine the person

holding the bottle would reçeive a severe shock w h e n afinger of the free hand touched the central rod.

The news of this discovery spread SO rapidly throughEurope that within a very short time it had been repeated

everywhere, and some individu& traveled throughout thecontinent demonstraling the new discovery, and gaining a

good livelihood thereby. In England Sir William Watson

showed the Leyden jar to Dr. Uevis, a colleague, wbo sug-gested coating the outside with sheet lead or t in foi1 t o

r e p l a c e t h e human hand. Another experimenter, J o h nSmeaton, applied tin foi1 to both sides of a pane of glass

and obtained excellent results, whrreupon Watson coatedboth the inside and the outside of several large glass jars

with leaf silver arrd succeeded in storing powerful charges.

THE SPEED OF ELECTKICITY

‘The Leyde” jar provided a new and useful tool for carryingon electrical research, especially experiments in the trans-

mission of electricity. By this time the use of wires as con-ductors was commcmplace. In F r a n c e electricity fromcharged Leyden jars was transmittcd a distance of 2% miles.P i e r r e C h a r l e s Lemmonier, the French astronomer, at-tempted to measure the velocity of electricity but fond

that the time required to travel a distance of 5700 feet wasinappreciable. In England Sir \Villiam Watson, together with

Henry Cavendish, Dr. Ilevis, and others, conducted similarexperiments using the ground as one side of the circuit .

Baked or dried sticks were used as supports for the wires.On August 5, 1748, at Shooters Hill, these men set up a cir-

cuit of 12,276 feet through which they discharged a Leydenjar and decided that transmission was instantaneous.

20 Chapter Two

SIR WILLIAM WATSON3 THEORIES

In another experiment, Watson observed that bodies un-equally charged with the same kind of electricity tend toequalize their charges when they are joined. Watson wasalso the first to apply the terms plus and minus to electricalpolarities; therefore, he may have shared Franklin’s viewthat there was, in fact, only one kind of electricity and thatthere appeared to be two kinds due to a relative excess ordeficiency. Watson was the author of several books on elec-tricity, one of which, published in 1746, entitled Naturead Properties of Electricity, first aroused Franklin’s in-terest in the subject.

MISCELLANEOUS DISCOVERIESProbably the first attempt to use electricity for telegraphicpurposes over long circuits was made by Johann HeinrichWinckler of the University of Leipzig in 1746. In some ofhis experiments he used the river Pleisse for a portion of thereturn circuit. Following the work of Gray and Du Fay onthe transmission of electricity, the idea of using electricityfor telegraphic purposes occurred to a number of men. Be-fore the discovery of voltaic electricity and electromagne-tism the kinds of signais were limited in number. Wincklerprobably used sparks.

Pierre Lemonnier of France discovered that the quantityof electricity communicated to a body is not in proportionto its volume but in proportion to its surface. He also dis-covered that the shape of a body influenced its ability toreceive a charge.

The Abbé Nollet (Jean Antoine 1700-1770), who was thefriend and co-worker of Du Fay, made numerous discov-eries and observations. He found that when an uninsulatedbody was introduced into an electrical field of influence it

Experimenls with Statk Klectricity 21

became electrified. This effect had also been noted hyGray. Nollet observed that when sbarp points were broughtinto such a ficld, the sharpest were first to give off brushesof light. He may also have been the inventer of an electro-scope consisting of two threads attached to a conductor,which diverged when electrified.

‘The Abbé also performed numerous experiments on theinfluence of electricity on the flow of liquids from capillarytubes. Nollet called attention to the similarity between elec-tricity and lightning, as Dr. Wall, Stephen Gray, Winckler,and others had done.

There had heen little interest in magnetism since the timeof Gilbert, but there was one new development. Knight andMichel1 in England, and Duhamel in France, during t h eyears 1745 ta 1750, had constructed several powerful steelmagnets by new processes of heat treatment and by the useof a number o f smsller ba r s t o bu i ld up a single largermagnet. The principal source of magnetism, however, wasstill the lodestone, except that some rather weak magnetshad been made by striking steel bars held in the magneticmeridian.

The discovery had been made about this time that a cor-rent of air issued from an electrified point at the same timethat such a point gave forth a brush discharge. Hamilton ofDublin used tbis discovery to construct the first electricallyoperated motor, wbich consisted of a wire stuck through aCork with the pointed ends bent in opposite directions. Theaxis was a needle that was suspended from a magnet SO thatit could turn almost without friction. When the points wereelectrified the device rotated SO long as the electrificationcontinued.

Benjamin Wilson made a somewhat similar device, exceptthat he provided vanes on thç Cork set in motion by a

22 Chapter Two

stream of air issuing from an electrified point placed justoutside them.

Hawksbee, Nollet, and others had observed the similaritybetween electrical discharges in a vacuum and the auroraborealis. Perh Vilhelm Margentin, secretary of the SwedishAcademy of Sciences, addressed a letter to the Royal Soci-ety, dated February 21, 1750, in which he mentions hisobservations concerning the effect of the aurora borealis onthe magnetic needle. If, as some believed, the aurora bore-alis was an electrical phenomenon, this discovery by Mar-gentin established a relationship between electricity andmagnetism. The discovery had also been made that piecesof steel that had been struck by lightning were sometimesmagnetized.

B E N J A M I N FRANKLIN3 EXPERIMENTSBenjamin Franklin (1706-1790) of Philadelphia was thefirst American who made a notable contribution to elec-trical science. His fame in science rests chiefly on his dem-onstration that lightning was an electrical discharge, butthis discovery had been anticipated by others, both intheory and in experiment. His well-known kite experimentwas performed in June 1752, during a thunderstorm in afield at the outskirts of Philadelphia. He succeeded incharging a Leyden jar from the kite string as it began to rainand a heavy thundercloud passed over.

Franklin had written at some length concerning his theo-ries regarding lightning and his proposed methods of prov-ing them. These writings were published abroad before hewas able to perform his experiment, with the result thatothers were soon engaged in similar endeavors. In France,Dalibard and Delor proved the electrical nature of lightning

Figure 2.2 Benjamin Franklin (Iirom Smithsonian InstitutionJ

24 Chapter Two

about a month before Franklin’s kite experiment, by meansof elevated rods from which Leyden jars were charged.Canton and Wilson, in England, carried on similar experi-ments with good results, and in St. Petersburg, ProfessorRichmann was killed by lightning while experimenting withan elevated rod during a thunderstorm.

Other experiments performed by Franklin were probablyof greater lasting importance. He began his work in elec-tricity in 1746, at which time he had purchased somesimple pieces of equipment after reading a book on thesubject by William Watson. Perhaps his earliest discoverywas the fact that when a piece of glass was rubbed with acloth, the glass received a charge of the same strength as thecharge on the cloth but opposite in kind. He concludedthat a11 bodies contain electricity, and that when two dis-similar substances are rubbed together the one receives anexcess of electricity and the other a deficiency. From thissupposition he reasoned further that there was but one kindof electricity rather than two, as Du Fay and others hadsupposed. Dr. Watson in England may have corne to thesame conclusion when he spoke of plus and minus electric-ity, terms that were very similar to Franklin’s positive andnegative.Franklin demonstrated his theory concerning a single kind

of electricity by having two people stand on insulated plat-forms, one of whom rubbed a glass tube with a cloth andtook the charge from the cloth, while the other took thecharge from the glass. When they brought their fingers closetogether a strong spark passed between them and both werecompletely discharged, showing that the charges had neu-tralized each other. Another demonstration of the sameprinciple was made by hanging a Cork bal1 between twoknobs connected to the inner and outer linings of a Leyden

jar. The hall would vibrate between the two knobs until theLeyden jar was eompletely discharged and hoth coatingswcre neutral with respect to the earth.

When a Leyden jar is charged, thc outer coating must beconnected to ground or to some other eyuivalent body.Franklin showed that the inner coating Will receive only asmuch electricity as is driven from the outer ooe. He notcdthat a linen thread, suspended near the outer coating, wasunaffected until the eyuilibrium was disturbed by bringinga finger ncar the knob connected to the inter coating.

Franklin showed also that, apparently, the charge held bya Leyden jar was on the glass and not in the coatings. Hedemonstrated this theory with a jar in which water formedtbe inner coating. When the water was poured off, he foundthat tbe water was not charged. Upon filling the jar withfresb water he was able to discharge it. Franklin performedsimilar expetiments using glass plates with removable coat-ings. Later research has shown that although the facts ofthe experiment werc correct, the interpretation is slightlydifferent. It is now known that the charge is of the natureof a strain in the dielectric.

In 1748, Franklin descrihed an electrostatic jack, or mo-tor. HC attached two metal knobs to diametrically oppositesides of an insulating wheel and placed tbe wheel SO that itwould rotate between two stationary insulated knobs, witha vcry small clearance between the rotatiog and stationaryoncs. When the stationary knohs wcre electrified, onc posi-tively and the otber ncgatively, the wheel was caused torotate. The knobs on the wheel were fiat attracted, and ast h e y a p p r o a c h e d t b e stationary knohs a spark passed,making the charge on both of the samc sign. The result wasthat they repelled one another and caused the wheel torotate.

26 Chapter Two

ATMOSPHERIC ELECTRICITYOn April 12, 1753, Franklin succeeded in causing an alarmbel1 to ring by means of atmospheric electricity. He hadinstalled an insulated iron rod at his house, which projectedsome distance into the air. The rod was connected to adevice in which there were two bells, with a lightly hung,insulated clapper between them. One of the two bells wasconnected to the elevated rod and the other to ground.When the rod became sufficiently electrified, the clapperwas attracted first to one bel1 and then to the other.

The elevated rod served for various other experiments in-volving atmospheric electricity. He found that the chargeon a cloud might be either positive or negative and that acloud could change the polarity of its charge. Franklin ob-served strong electrification of the atmosphere during asnowstorm and even when the sky was entirely clear.

In another series of experiments, Franklin became inter-ested in the nature of the electric field surrounding acharged body. In order to visualize the shape of the field,he suspended electrified bodies in still air, and then filledthe air with smoke from rosin, which he had dropped onhot plates. The smoke, much to his amazement and gratifi-cation, formed beautiful patterns about the charged body.

Franklin had a friend at Boston, a Mr. Kinnersley, whowas also interested in electricity. They corresponded fre-quently concerning their experiments. Kinnersley redis-covered Du Fay’s findings concerning two kinds of elec-tricity by the use of two electrical machines, one with asulfur ball, and the other with a glass globe. Neither of thetwo men knew of Du Fay’s work. Franklin repeatedKinnersley’s experiment, and observed that the sparks fromthe glass and sulfur balls were different in appearance. Thebrush discharge from the prime conductor of the glass globe

machine was large, long, and divergent, and made a snap-ping noise, whilc that from the sulfur machine was short,small, and m a d e a hissing n o i s e . Kinnersley also experi-mented with tbe thermal effects of electricity, and by usinga battery of Leyden jars he succeeded in melting fine ironwires.

For his many achievements in electrical science, Franklinwas awarded the Copley Medal, Enghmd’s greatest scientificaward, hy tbe Royal Society of London in 1753.

EXPEKIMENTS IN EUROPE WlTHATMOSPHERIC ELECTRICI'I'Y

Lemonnier, the Abbé Mazeas, and Beccaria, during theyears 1752 and 17 .53 , performed many experiments onatmospheric electricity using botb kites and elevated rods.‘They found evidences of electrification at most tirnes, butespecially when them were thunderclouds in the sky. Usu-ally there was Little electrification at night, but it increasedgrcatly after sunrise and diminisbed after son&.

Canton discovered tbat the air in a room could be electri-fied, as did Heccaria also. Canton showed that the air in azoom acquired the same kind of electricity as a chargedbody in that room and that the divergence of two threadsattached to the charged body gradually decreased as tbe airbecame electrified, even though the charge on the body wasmaintained hy an electrical machine. Beccaria producedsparks under water and noted tbe fo rma t ion o f buhblesaccompanying the sparks hut did not suspect that the bub-hles were due to the decolrlposition of the water

ELECTRICAL INDUCTIONElwtrical induction is the phenomenon in which a bodybecomes electrified when it is approached hy another body

28 Chapter Two

carrying an electrical charge. Its effects had been noted byHawksbee, Stephen Gray, Nollet, and probably by manyothers. It was now under investigation by Franklin, Wilke,Canton, and Aepinus. Experiments had shown that when acharged body was brought near an insulated conductor, acharge similar in kind to that of the charged body appearedat the remote end of the insulated conductor (repelledcharge), and that if this charge were led off to ground andthe original charged body removed, there remained on theinsulated conductor a charge (bound charge) of sign oppo-site to the original one. Stephen Gray had in part discov-ered similar effects with his packthread line but had notobserved the relationship of kinds, nor that there were twodistinct induced charges. The discovery of inductive effectsled to the invention of the electrophorus in 1775 by Ales-sandro Volta. It consisted of a flat metallic disk, or shallowpan, which was covered with sealing wax or rosin and pro-vided with a removable disk of metal, of slightly smallersize, having an insulating handle at the tenter. When thesealing wax or rosin was electrified by rubbing with a cat-skin and the removable disk was brought down near thesurface of the charged electrophorus, induced charges wereproduced in the disk. By touching the finger to the remov-able disk before it was lifted, the repelled charge was ledoff, after which the finger was removed and the disk lifted,which then had on it a free charge. The electrophorus was auseful instrument, because it provided rather large quanti-ties of electricity with little effort.

ELECTROSCOPESThe Reverend Abraham Bennet described in the Philosoph-

id Transactions for 1787 two inventions of great impor-tance. One was the gold leaf electroscope that, with subse-

Figure 2.3 Coulomb’s Torsion Balance (Courtey Burndy Library)

30 Chapter Two

quent improvements by William Hasledine Pepys, becamethe most sensitive detector of electricity, and the other washis electric doubler, a device that by induction was capableof building up a small charge to a large one.

In connection with the gold leaf electroscope, mentionshould be made at this time of the various other electro-scopes and electrometers which came into use. The earliestwas probably Gilbert’s versorium, a pivoted needle. VonGuericke, Stephen Gray, and others had used feathers toindicate electrification. Nollct, Beccaria, and Franklin usedtwo threads hung close together, which separated whenelectrified. It is not clear who invented the pith bal1 electro-scope, but such instruments were in use by the middle ofthe eighteenth Century. Daniel Gralath, of Danzig, aboutthis time, had constructed an electrical balance. William T.Henley, in 1772, invented the quadrant electrometer, usinga pith bal1 suspended at the tenter of a graduated arc.

By far the most important device of this kind was thetorsion balance, invented about the year 1784 by CharlesAugustin de Coulomb (1736-1807). John Michell, whosename was mentioned previously in connection with mag-nets, had described a torsion balance earlier which Caven-dish used to determine the mean density of the earth.Coulomb used the instrument to prove the inverse squareslaws governing electric and magnetic fields. This law hadbeen announced for magnetic fields by Johann TobiasMayer at Gottingen in 1760, and for electrical fields byCavendish in 1762, but in each case with only partial proof.

Coulomb demonstrated with great accuracy that the forcebetween two magnetic poles is proportional to the productof the pole strengths and inversely proportional to thesquare of the distance between them, and that the forcebetween two electrical charges is proportional to their prod-

uçt and inversely proportional to the.square of the distancebetween them. These laws are expressed in later terms bythe equations f = mm’/($) and f = qq’/(K?), in whichfis thç force, m and m’ are thr magnetic polc strengths,p (the Greek letter mu) is the permeability of the interven-ing medium, r is the distance between the magnetic poles orelectrical charges, q and q’ are the electrical charges, and Kis thç dielectric constant.

Coulomb’s use of the torsion balance marked the begin-ning of quantitative work in electricity and magnetism.Coulomb also devised a magnetometer f o r measuring t h eintcnsity of the earth’s rnagnetic field. Charles Borda, aE‘rencb astronomcr, had made cer ta in magnrtic measure-ments with some success in 1776, and still carlier GeorgeGraharn had suggested methods of measurement but hadnet carried t h e m out.

OTHEK DISCOVERIES IN ‘~LIE EIGHTEENTH CENTURY

During the closing years of tha eighteenth Century therewere many discoveries of varying degrees of importance.Georg Christoph Lichtenberg, professor of experimentalphilosophy at Gottingen notrd in 1777 that when finepowders, such as lycopodium spores, were electrified anddusted upon surfaces electrified with the opposite kind ofe l e c t r i c i t y , the particles arranged themselves in beautifulconfigurations. The positively charged powders showed fig-ures resembling feathers, while thosc negatively electrifiedarrangcd themselves in starlike figures. Thcse are known asLichtenberg figures and are at present produced moreclearly on photographie plates.In 1781 Lavoisier, the gxat French chemist, showed that

electrification was p roduced when solids o r liquids were

32 Chapter Two

converted into gases or when gases were released duringeffervescence caused by chemical action.

Martin Van Marum, of Holland, about 1785 constructedthe most powerful frictional electrical machine built up tothat time. It was a plate machine, having two circular glassplates 65 inches in diameter, each of which was excited byfour rubbers. SO powerful was this machine that a pointedconductor at a distance of 28 feet showed a brush dis-charge. Van Marum also constructed a battery of Leydenjars with a total surface of 225 square feet. The dischargefrom this battery magnetized steel bars l/iz inch by 1 inchin cross section and 9 inches long.

The magnetic properties of cobalt and the diamagneticproperties of bismuth and antimony were discovered in1778 by Sebald Justin Brugmans of Holland. A diamagneticsubstance is one that has a permeability in air or in a vac-uum of less than one. A bar or needle of such a substancewhen free to move would tend to take a position at rightangles to the lines of force in a magnetic field.

Before concluding the portion of this history precedingthe epochal discovery of the voltaic cell, mention must bem a d e o f J o s e p h P r i e s t l e y (1733-1804). H i s fame t .tschiefly on his discovery of oxygen, but he carried on aconsiderable amount of electrical research and wrote thefirst electrical history entitled The History and PresentState of Electricity. This book of 736 pages was publishedin 1767, and notwithstanding the fact that electrical sciencehad scarcely been born at this time the book is still wellworth reading.

Priestley made only minor contributions to electricalscience, among them the fact that carbon was a conductor,yet he showed a remarkable insight into the nature of elec-trical phenomena and predicted that new developments in

the art would far outstrip anything that had SO far beenconçeived. He could hardly bave dreamed of the magnifi-cent fulfillmcnt of h is prophecy.During the period whose his tory has bcen traced in this

chapter, electricity had advanced from the pos i t ion of acurious a n d m y s t e r i o u s phenomenon, about w b i c h verylittle was known, tu the foremost position in scientific in-

terest. The long list of experimenters, already mcntioned,h a d transformed electrical knowledge from a natural curi-osity into a science. Notwithstanding the great progress that

h a d b e e n a c h i e v e d , tbere was net yet a single practicalapplication of electricity, unless the lightning rod, Frank-

lin’s electrostatic bells, or the whirligigs of Hamilton, Wil-son, and Franklin could be considercd as such.

3

Voltaic Electricity,Electrochemistry,

and Electromagnetism

The closing decades of the eighteenth Century were years ofunusual importance to electrical science. Up to that time a11known electrical phenomena originated solely from electri-cal charges produced by friction, heat, or induction, andcurrents of electricity were of a transitory nature, resultingfrom the discharges of accumulated electrical charges.

In the period now under consideration, new contrivanceswere discovered which were capable of producing, by chem-ical means, steady currents of electricity. The quantities ofelectricity available from the various electrical machinespreviously in use were minute, and therefore the chemical,heating, and magnetic effects were difficult to observe, al-though a11 of them, as a matter of fact, had been noted.

On numerous occasions, important electrical discoverieshad been made without recognition of their value, and onlyafter one or more rediscoveries of such phenomena did theylead to new advances. Such was the case in the discoveriesmade by Galvani and Volta.

In 1700, Joseph, a Frenchman, and Caldani, an Italian,had noted the contractions of the muscles of a frog underthe influence of electrical discharges. In 1752 Swammer-dam, a Dutch physicist, published his account of an experi-ment in which a muscle was made to contract whentouched at two points, one of which was a nerve, with thefree ends of a silver and copper couple, the other ends ofwhich were joined.

Johann Georg Sulzer, of Switzerland, published in Berlin,in 1762, the discovery which showed that when unlike met-

ais such as silver and lead were held together on the tangue,a taste like that of iron sulfate was produced, and when onewas held on the tangue and the other below it, there was nosensation until the outer edges of the met& came in con-

I tact.GALVANI’S FROG EXPERIMENTS

Luigi Galvani (1737-1798), professor of anatomy at theLlniversity of tlologna, was not ordy a skilled anatomist buthe was also familiar with chernical and physical sciences.During the year 1780, while he was dissecting a frog in hislaboratory hefore a group of people including his wifeLucia (daughter of Domeniço Galeazzi, Galvani’s professorof anatomy) and Giovanni Aldini, his nephew, Galvani laidthe frog on the table near an electrical machine that wasbeing used at the time in performing electrical experiments.It was noted that when tlrere was a spark, while at the sametime a scalpel was held with its point at a nerve center, thelegs of thc frog contracted. According to one version of thestory, it was Galvani’s wife that called his attention to theunexpected happening.

Galvarri bccame greatly interested in this rather astonish-ing phenomenon, especially sincc there was no direct con-nection between tbc machine and the scalpel or tbe frog.He did not attempt to explain the latter circumstance, buthe recognizcd tbe fact that the contractions werc due toelectricity. Galvnni tried various met&, other than the steelknife, with similar results. Ile also obtained the same resultswitb a charged Leyden jar, witb tbe electrophorus, and withatmospberic electricity. In the course of these experimentshe bad prepared a number of pairs of frog’s legs whicb herrmunierl r>n hrass or copper hooks, pnssing through tbespinal tord, nnd had hung them opon an iron railing. HC

36 Chapter Three

Figure 3.1Libmy)

Luigi Galvanïs Frog-Leg Experiment (Courtesy Bur,

found that there were contractions of the muscles whensorne part of the teg came in contaet with the iron raiting,

not only during storms when there were flashes of tightningbut atso when there was a ctear sky.

These observations ted to further experiments in whichGatvani used potished iron and copper hooks or rods, and

atso silver and tin. He was convinced that he was observingthe effects of etectricat charges sornewhcre in his apparatusand decided that the muscles or nerves tbemselvea were tbe

source of the etectricity. He continued bis experiments foreleven years before pubtishing, in 1791, an account of his

observations. Before the publication of bis experiments,

however, others had tcarned of Gatvani’s discovery and re-peated them.

VOLTA AND THE VOLTAIC PILEAmong those who hecame interested in this matter was

Atessandro Votta (1745-X27), professor of natural historyat the University of Pavia, wbose name was mentioned pre-viousty in connection with the etectrophorus. Votta wazconvinced by his experiments that the source of etectricity

was not in the nerves or muscles but in the met& Gatvani,

however, showed that it was unnecessary to use met& atatt. He found that contact of one of the nerves with the

outer covering of one of the muscles was sufficient to causecontractions.

Gatvani and Votta each drew to himsetf fottowers whosupported the theories of their leaders and regarded as rankignorance and heresy tbe theories of the other camp. The

dehate waxed hot and was never settted to the entire satis-faction of eithcr side. Apparentty there was truth on bothsides, but it was Votta’s ideas which finalty ted to important

resutts.

38 Chapter Three

Figure 3.2 Alesandro Volta (Courtesy Bumdy Library)

Bath Galvani and Volta continued their experiments, butGalvani died in 1798 and did net live to sec the full fruition

of his work. Aldini, who had worked closcly with Galvani,and who had bcçomc professor of physiçs a t Uologna in

1798, carried on Galvani’s researches. Ile published severalpapas on the subject and became thç chief protagonist of

Galvani’s cause. Volta may bave invented the pile whichbears his name as early as 1792, but the invention was netmade public until Mach 20, 1800, at which time Volta

addressed a letter on the subjcct to the Royal Society of

LondonVolta’s pile, or the voltaic pile, as it is more commonly

called, took thr form of a cylindriçal stack, in which therewas first a zinc disk, then a disk of fclt, paper, or leather,soaked in a sait solution or dilute acid, then a copper disk,

another zinc disk, another pad, and uo on.In his letter to thc Royal Society, Volta descrihed thc

behavior of the pile as similar to that of a feebly chargedLeyden jar, but unlike that of the Leyden jar, the pile’scharge was not dissipated hut was constantly renewed. HC

observed that a spark was produced when wires connectedto thc two ends of the pile wcrc brought together. Voltaregardrd this discovery a s t h e expcrimental proof of h i scontention that the source of the electricity in Galvani’s

cxperiment was in the contact betweerl dissimilar met&Volta also deviser1 what was known as his couronne des

tasses (crown of cups), in which striys of copyer and zincwere hung wcr the edges of the çups and were partly im-

mcrsed in a sait or acid solution. ‘The coppcr strip in onecup was connected by means of a wire to the zinc strip ofthe next, and SO on. When a connection was made between

the zinc strip of thç last cup and the coppcr strip of the

first, a spark could he obtaincd, as with the pile.

40 Chapter Three

Figure 3.3 Volta’s Pile (Courtesy Bumdy Library)

Votta apparently believed in the contact theory, even afterconstructing his couronne des tasses. Other experimenters,however, went ta work immediately, and by October 1800Sir Humphry Davy hsd proved that the electricity was dueto chemical action and tbat the voltaic cell would not oper-ate with pure water. Ca&le and Nicholson diseovered thedecomposition of water on May 2, 1800, using a voltaicpile. In Juty 1800, William Cruikshank decomposed salts bysimilar means.

In November 1800, Volta went to Paris, wbere he lecturedon galvanism and illustrated his lectures with erperirnents.Among other things he decomposed water with curentfrom h i s cetls. Nspoleon recognized the impor t ance o fVolta’s diseovery and awarded him a gotd medal, the cuxsof the Legion of Honor, and a prix of 6000 francs.

EVOLUTION OF THE BATTERY AND DISCOVERIESWITH ELECTRIC CURRENTS

In 1801 Johann Ritter developed the idea of a series ofmet& from which the relative electrical pressures pro-duced by various pairs when immersed in a sait or acidsolution could be determined. Volta conceived the sameidea independentty at a later date, and the series came to beknown as Volta’s etectromotive series. These ideas indicatedthat the notion of electromotive force was already estab-lished, although a quarter of a Century was yet to elapsebefore the emmciation of Ohm’s law.

Kew developments came with great rapidity, and Voltahimself had scarcety dreamed of the immense field tbat hisdiscovery had opened . Cruikshank cons t ruc t ed a verypowerfut battery by soldering together plates of the samesize of copper and zinc and using these bimetallic plates as

42 Chapter Three

separators between compartments in a trough., The troughwas built of wood and was coated witb pitch. In it wereslots into which the separator plates were tightly wedged,and the intervening spaces were filled with a dilute sulfuricacid solution.

This battery produced very strong currents of electricity,with which it was possible to burn iron wires, heat charcoalto incandescence, and vaporize gold and silver leaf. Theeffects were, in many ways, much more powerful thanthose of the older electrical machines and Leyden jars,while in other ways the effects were not SO great and lessspectacular. The batteries produced only small sparks andhad little effect on the nervous system; they did, however,produce very great heating and chemical effects. Since theelectricities of the voltaic cells, and the older electric ma-chines seemed totally unlike, the electricity obtained fromthe machines was for a time called common electricitywhile that of batteries was called voltaic electricity.Experiments with the new voltaic cells were carried for-

ward in many places. Sir Humphry Davy (1778-1829), oneof the most brilliant scientists of his age, in his first lectureat the British Royal Institution, delivered on April 25,1801, discussed the history of galvanism. In a paper pre-sented in June of that year, he showed that galvanic actioncould be produced from plates of a single metal in differentfluids, which were, however, in contact with each other.

Nicholas Gautherot, in 1801, discovered that when a cur-rent of electricity from a voltaic battery was sent throughtwo copper plates in sulfuric acid, for a short time theseplates became capable of supplying a current in the oppo-site direction. Ritter, between the years 1803 and 1805,constructed several secondary batteries using copper, gold,and other metals as electrodes. In 1802 Luigi Valentino

Brugnatelli, a friend and pupil of Volta, discovcred electro-plating, with the use of the voltaic pile.Volta’s first pile was a puy affair, and the immediate

reaction of other scientists, who became interested in the

matter, WÛS to build larger and still luger batteries. Several

learned societies, among thcm the Koyal Socicty, appropti-

ated funds for the construction of such batteries, sorne ofwhich were huge things, weighing tons.

William Haslcdine Pepys constructed several very large hat-teries for the Royal Socicty between the years 1802 and

1808, using copper and zinc plates in a nitric acid solution.Dr. Wollaston also huilt several huge batkries, and Dr.

Robert Hare of the University of Pennsylvania constructed

Figure 3.4 Wollaston's Pile. This great electroehçmical pile wasbuilt by the Royal Institution in London with funds provided bypublic subscription in 1813. It was inknded as a rival to the pile of600 couples built by the order of Napoleon in Paris and was uaed byHumphry Davy for his experiments. (Courtes~ Burndy Librory)

44 Chapter Three

batteries strong enough to fuse large pieces of metal. Therewere also batteries of great size at Paris and smaller ones atmost of the universities of Europe.

Nearly a11 of these batteries were constructed of the samesimple elements, and they were a11 subject to the defectcalled polarization. Polarization refers to the collection ofhydrogen gas bubbles on the positive electrode, causing theinterna1 resistance of the ce11 to increase, and setting up acounter electromotive force, thereby diminishing the out-put.

After Davy had proved the chemical nature of the voltaicce11 and other experimenters had succeeded in decomposingwater, there developed a great interest in the chemicalaction of the voltaic current. Berzelius of Gotland, Sweden,between the years 1802 and 1806, published a number ofimportant papers on his electrochemical researches. Thesepapers undoubtedly laid the foundation for the brilliantseries of electrochemical discoveries by Davy.

On November 20, 1806, Davy delivered his first Bakerianlecture before the Royal Society, on the subject, “On SomeChemical Agencies of Electricity,” and thereby providedthe basis for the ionization theory. Then followed that not-able series of discoveries in which Davy isolated sodium andpotassium in 1807 and barium, boron, calcium, and stron-tium in 1808.

Funds for a powerful new battery for the Royal Institu-tion were subscribed in 1809. With this battery Davy sepa-rated the halogens, iodine, chlorine, and fluorine. Theseelements had, however, already been isolated by others. In1810, Davy for the first time exhibited the carbon electricarc, using the battery as a source of electricity.

46 Chapter Three

ELECTROMAGNETISM

Hans Christian Oersted (1777-1851) was professor ofnatural philosophy at the University of Copenhagen. Asearly as 1812 he expressed the helief that magnetic fieldswere associated with electricity, but this statement was byno means a new doctrine, for electricity and magnetism hadlong been considered as having something in common,probably as far back as Thales. There was already muchevidence that the two were related, such as the fact thatpieces of steel had been magnetized by strokes of lightningand steel needles had been magnetized by discharges fromelectrical machines. Boze, in a letter to the Royal Society,stated that he had reversed polarities in a magnet and haddestroyed magnetism by means of electricity. Beccaria hadcommented that the earth’s magnetism might be due to thecirculation of the electric fluid about the earth. Franklinknew that lightning produced magnetic effects.

Romagnosi, in 1802, had observed the deflection of amagnetic needle in the presence of a conductor carrying anelectric current, but he seemed to have attached no impor-tance to his discovery at the time, and certainly no resultscame of it. Romagnosi himself made no claims to priorityin the discovery of electromagnetism.

In 1819, Oersted was lecturing before a science classwhere he demonstrated the heating effects of voltaic elec-tricity. During the demonstration he noted the oscillationsof a nearby compass needle, which corresponded with theopening and closing of the electrical circuit. Oersted spentsome months with further experiments on this phenome-non, using stronger batteries in order to obtain greater de-flections of the needle. He found that not only was a com-pass needle deflected by the electric current, but a wire

Figure 3.6 Oersted’s Diseovery (Courtesy Bumdy Librwy)

48 Chapter Three

carrying a current of electricity, when free to move, wasdeflected by a magnet.

Oersted’s great discovery was published in a Latin mono-graph dated July 21, 1820. The effect on the scientificworld was like that of von Guericke’s electric machine orvon Kleist’s Leyden jar, for it was news of the greatestimportance, and Oersted’s experiments were repeated bymen of science everywhere.

AMPÈREAndré Marie Ampère (1775-1836) discovered that therewere forces between two wires carrying electric currents.He supported a loop of wire with its terminals dipping intomercury cups. When a current of electricity was sentthrough this loop and an adjacent stationary loop, the sus-pended loop was deflected through an angle. Between Sep-tember 18 and November 2, 1820, Ampère delivered aseries of lectures at the French Academy, describing newdiscoveries in electromagnetism. He defined the relationshipbetween the direction of current flow and the deflection ofa magnetic needle, and he showed that parallel conductorscarrying currents in the same direction attracted each other,while those carrying currents in opposite directions weremutually repelled. He also constructed a lightly suspendedhelix of wire and showed that when an electric currentpassed through it, the helix behaved like a compass needleand like a magnet with respect to other magnets. He devel-oped the astatic needle, in which the effect of the earth’smagnetism is neutralized, advanced the theory that themagnetism of permanent magnets might be due to electriccurrents in their ultimate particles, and suggested that elec-tromagnetism might be used for telegraphy.

ARAGD, BIOT AND SAVARTArago discovered, in 1820, that a wire carrying a current ofelectricity would attract iron filings. lie and Ampère bothdiscovered that a wire helix carrying an electriç curent wascapable of magnetizing a soft iron bar around whiçh it waswound. In the same year Biot and Savart announced the lawgoverning the force between a long straight conductor and amagnetic pale which is expressed by the equation H = 2i/r,in which H is the magnetic field strength, i is the current,and r is the perpendicular distance Crom the point of mea-surement to the conductor that caries the current.

FARADAY'SROTATINGCONDUCTORANDMAGNETANDBARLOW'SWHEEL

On September 3, 1821, Michael Faraday discovered tbat aconductor çarrying a curent would rotate about a magneticpale and that a magnetized needle would rotate about awire çarrying an electric current. For the first experiment,he used a metal cup containing mercury in thc tenter ofwhich was a vertical bar magnet, one of whose pales pro-truded above the surface of the mercury. The conductorwas lightly suspended above the cup, with the lower enddipping into the mercury. When a current was sent throughthe conductor, it revolved about the magnetic pale. For thesecond experiment, Faraday used substantially the sameequipment except that the conductor was held in a fixedposition, touching the mercury at the çenter of the cup, andthe magnet was a magnetic needle, one end oî which wasweighted with platinum, so that one pale restcd upon thebottom while the other end floated freely in the mercury,with the pale projecting above the surface of the mercury.$Vhen a cunent was sent through the conductor into themercury, the magnetic needle rotated about the conductor.

50 Chapter Three

At about the same time Faraday discovered that a metaldisk mounted on an axis through its tenter with its loweredge placed between the poles of a horseshoe magnet wouldrevolve when a current passed between the axis and atrough of mercury into which the lower edge dipped. PeterBarlow had made a similar motor a little earlier, and thedevice was therefore called Barlow’s wheel.

STURGEON’S ELECTROMAGNET

Sturgeon is credited with making the first electromagnet in1821, although Ampère and Arago had noted the magneticfields of helices and their ability to magnetize soft iron.Professor Joseph Henry, of Albany, New York, was the firstto make electromagnets with superimposed layers of insu-lated wire. His magnets were of high intensity and greatlifting power.

GALVANOMETERS

Schweigger and Poggendorff, during the years 1820 and1821, constructed the first crude galvanometers, using awire helix and a compass needle. The earliest instrument ofthat type was called a multiplier, because the effect of asingle wire on a compass needle was multiplied many timesby the use of a helix.

AMPÈRE3 AND OHM’S LAWS

Except for Coulomb’s torsion balance, previous measuringinstruments were scarcely more than indicators. Improve-ments were soon made in the Schweigger and Poggendorffgalvanometers SO that they became measuring instrumentsof great accuracy. After Ampère published his fundamentallaw governing the relationship between an electrical circuitand a magnetic field, it became possible to use the galva-

nometer f o r accurate measurements o f electric currents.‘This law, which was published in 1822, is as follows:f=i . m . dslr’,’ m which fis the force produced by a cur-rent i and a magnetic pale strength m; ds is an incrementallength of conductor, which is perpendicular to the line join-ing the conductor and the magnetic pale and separatedfrom it by a distance of r centimeters. From this law maybe derived a definition of the absolute unit of currentstrength.

Georg Simon Ohm (1787-1854) began his study of elec-trie currer~ts, flowing through conductors, in 1825. He pub-lished thc resutts of his studies in 1827, and in his papa,thc taw, which now bears his name, was presented for tbefirst time. In present-day international symbols, tbis lawreads I = V/R- whcrc I is the currcnt, Vis thc electromotiveforer or voltage, and K is the resistance.

‘IXe benvy curtain, which for SO long had obscured inrnystery tbe nature of electriçity and magnetisrn, had beenpulted aide just a lit&, but most of nature’s geat secretwus s t i t t h i d d e n . Tbere were at band, however, two newprophets in the temple of science, who soon were to openthe curtain much wider.

4

Faraday and Henry

FARADAY3 FORMATIVE YEARSMichael Faraday was born at Newtington Butts, South Lon-don, September 22, 1791. His father, James Faraday, was ajourneyman blacksmith. Michael’s formal education endedat the age of thirteen, at which time he took employmenton a tria1 basis with a Mr. Riebau, a bookseller, in Bland-ford Street. After a year he became apprenticed to Mr.Riebau for a period of seven years. During his apprentice-ship, Faraday became a skilled bookbinder, and at the sametime he developed an absorbing interest in the sciences, andparticularly in chemistry. His bent toward science had itsorigin in certain books, which passed through his hands inthe Riebau shop.

As a youth Faraday read widely, not only in the sciencesbut also in other fields of literature. He developed a certainfacility and beauty of expression that in later years becameone of his great assets. Faraday’s career in experimentalscience began with the acquisition of a few pieces of chem-ical apparatus. He attended several courses of popular scien-tific lectures and there made the acquaintance of otherYoung men whose interests were much like his own.

The event that changed the whole course of Faraday’s lifewas an invitation from a Mr. Dance, who visited the Riebauestablishment frequently, to attend four lectures by thethen famous Sir Humphry Davy. These lectures were de-livered on February 29, March 14, Apri18, and April 10,1812. Faraday made careful notes of the subject matters,which he later transcribed, and then bound into a book.

It was at about this time, when Faraday was twenty-oneyears of age, that he completed his apprenticeship with Mr.

Figure 4.1 Michael Faraday (From Smithaonion Institution)

54 Chapter Four

Riebau. Notwithstanding a deep affection for his master,Faraday had developed a dislike for his trade, but neverthe-less he took a position as a journeyman bookbinder with acertain De la Roche. The disagreeable nature of his new em-ployer caused Faraday to reach the definite decision that hehad no desire to remain a bookbinder. He confided hislonging for scientific work to Mr. Dance, who urged him toWrite to Sir Humphry Davy. Faraday followed his friend’sadvice, wrote a letter, and sent along the bound notes ofDavy’s lectures. Davy was impressed, and asked Faraday tocorne to him for an interview.

FARADAY APPOINTED TO THEROYAL INSTITUTION

Davy urged upon Faraday the thought that science was ahard and penurious master, but Faraday was not dissuaded.Davy apparently liked the Young bookbinder, for he recom-mended his appointment as a laboratory assistant. Faradaywas given the position at a salary of twenty-five shillings aweek, together with living quarters at the Royal Institution.

The appointment was made in March 1813, and on Octo-ber 13, 1813, Faraday left London to accompany SirHumphry and Lady Davy on an extended tour of the Con-tinent. They visited France, Belgium, Italy, Switzerland,and Germany, and in the course of their travels they metAmpère, Arago, Gay-Lussac, Chevreul, Dumas, Volta,de La Rive, Biot, de Saussure, de Staël, Count Rumford,and Humboldt. Faraday gained greatly in knowledge andwas very happy, except for the unpleasantness caused byLady Davy who treated him as a servant.

They returned to England on April23, 1815, and twoweeks later Faraday was again engaged at the Royal Institu-tion, as a laboratory assistant at a salary of thirty shillings

per week. During several years that followed, he worked atthe sidc of Sir Humphry in the laboratory, and also assisted

him at the lecture table. Faraday aided Davy in tbe develop-

ment of thç miner’s safety larnp and in nrany of the experi-rnents that Davy was pursuing. bot at the same time Fara-day carried on a certain amount of original research. In

1816 he presented a series of seven lectures before the CityPhilosophical Society on chemical srrbjects. Although hewas becoming known in a limited way, hc was so close to

the brilliant Davy that for a time his talents were obscured.On Jur~e 12, 1821, Faraday married Sarah Bernard, who

was a member of a religious sect çalled Sandemanians, ofwbich Faraday was also a member. Their marriage appears

to bave bcen very happy for botb, throughout their longlivcs.

When Oersted’s discovery o f electronlagnetisln waz a n -nounced in 1820, Davy brought a copy of the paper to the

laboratory immediately, where he and Faraday repeatcd theexperiments. Faraday was occupied at the time with mauyspecial problerns, including alloy steels, b u t h e seerns to

bave been muçh impressed with Oersted’s discovery andduring h i s leisure momcnti returned t o the experiment

many times. He made his first independent discovery afterbis marriage, namely, the rotation about a magnetic pale of

an etectrical conduçtor carrying a current. This discoverycarne on Septcmber 3, 1821, and on Christmas Day of the

same year he sbowed his wifc a conductor carrying a cm-rent rotating under the influence of thc earth’s magnetism.

During the year 1821, whiçh had been an eventful onc forFaraday, he was made superinteodent of the Royal Institu-

tion.In addition to bis lectures, experiments, administrative

duties, and researches for thr government, Faraday began

,

56 Chapter Four

to receive many requests for special research work, o f aprivate nature, some of which he undertook. The fees hereceived for this work might have made him wealthy, but

some years later he gave up such work altogether, becausehe felt that it was interfering with what he considered moreimportant projects.

Faraday’s mind reverted constantly to electrical and mag-netic problems. In 1822 he had written in his notebook thewords, “convert magnetism into electricity.” During theyears that followed, Faraday returned to this problem againand again. If his apparatus had been better, the discoverywould probably have been made in 1824 or 1825. In themeantime important work in other fields was bringing himrecognition. He had liquified a number of gases, includingchlorine, and had read a paper on the subject in 1823. In1824 he produced benzol, or benzine, and during that yearhe also began his researches on optical glass, which contin-ued until 1829.

In 1825 Faraday was appointed to the post of director ofthe laboratory and professor of chemistry at the lnstitu-tion. In 1826 he began his Friday evening lectures, whichwere to continue for many years, and during that year also,he began his Christmas lectures for children. On Decem-ber 3, 1827, Faraday took as his assistant Sergeant Ander-son who, until his death in 1866, worked faithfully at Fara-day’s side.

ELECTROMAGNETIC INDUCTIONIn 1824, Arago had noted that a certain very fine compass,which had had copper in the bottom of its cell, oscillatedfor only a short time when in its ce11 but when the needlewas removed it oscillated over a longer period. The copperwas tested and was found to contain no iron. Arago then

tried iotating a copper disk under a magnetic needle artdfound that the needle tended to follow the rotation of thecopper disk. It was found also that other met& exhibitedsimilar effects. Silver showed a greater effect than copper,while lead, mercury, and bismuth were less effective. Acopper disk was made to rotate by revolving a magnet nearit. Faraday and other researchers were aware of these phe-nomena but none çould offer a satisfactory explanation.

In September 1831 Faraday again attacked the problemof producing electricity from magnetisrn. His experimentsat this time are described in his Ezperimental Researches inElectricity. His first apparatus consisted of a wooden spool,o n w h i c h were wound twelve separate helices, insulatedfrom one another with calice and the individu1 turns sep-arated by a winding of twine. He connccted the even nurn-bered coils into one series and thc odd numbered coils intoanother. The one set of coils he connected to a battery andand the other set to a galvanometer. With a current flowingfrom the battery, he saw no effect on the galvanometer.Later, with a much more powerful battery, consisting of ahundred cells, connected to a single pair of insulated coils,he noted slight effects on the galvanometer when the circuitwas made or broken. The deflection was in one directionwhen the circuit was made and in the other direction whenit was broken. As long as there was a steady flow of curentfrom the battery, the galvanometer showed no effect.

His next experiment is generally considered as the one inwhich he proved conclusively that eleçtricity could be pro-duced from magnetism. HC used a welded iron ring 6 inchesin outside diarneter, of T/a inch soft iron rod. On one sectorof the ring he wound threc coils, covering about 9 inches ofthc çircunderence, and on arrother part he wound a singlecoil containingabout 60 fcet of copprr wire, about ‘120 inch

58 Chapter Four

in diameter. It should be noted that commercially insulatedmagnet wire did not exist until about twelve or fifteenyears later.

In Faraday’s description of his experiment, he designatedthe triple coi1 as “A,” and the single coi1 as “B.” The coi1“B” was connected to a galvanometer, and the three coilswere joined together, with the terminals connected to abattery through a switch. When the battery circuit wasclosed there was a powerful deflection of the galvanometerin one direction, and when the circuit was opened there wasan equally strong deflection in the opposite direction.

In his next experiment, Faraday dispensed with the bat-tery and instead made use of a very large compound mag-net. He mounted a helix on an iron bar, which extendedout beyond the helix on either side. As the bar carrying thecoi1 was brougbt near the magnet, it was drawn suddenly tothe poles. The galvanometer, which was connected to thecoil, was deflected violently as the bar was attracted to themagnet, SO that the needle spun around. When the bar waspulled suddenly away from the magnet, an equally violentdeflection of the galvanometer needle occurred in the oppo-site direction.

A single t-uï-Il uf cupper strip about the iron bar was suffi-tient to produce oscillations of the galvanometer needle.When the helix without the iron bar was moved across thefield of the magnet, there were wide swings of the galva-nometer needle, but the effect was much weaker than withthe iron tore.

Faraday made many variations of these experiments, inone of which he produced a steady current through a cop-per disk when it was rotated between the poles of a rnagnet.The galvanorneter connection was made between the axis ofthe disk and its periphery, with a sliding contact on the

latter. This device will be recognized as a unipolar gencra-ter and the reverse of Barlow’s wheel described in the pre-

vious chapter.Faraday used the current obtained by induction from his

coils to produce a spark between charcoal points, and withthe discharge from the same coils hc magnetized needles.

He also coostructed a simple loop of wire: whose terminals

were conneçted to two commutator segments, upon whichtw hrushes rested. When the loop was turned upon its axis

in a rnagnetic field, his galvanometer indicated a pulsating,unidirectional current.

It now became clear to Faraday what the significance waaof the damped swings of Arago’s compass needle and the

revolution of the needlc when placed near a revolving cop-per disk. Induced currents in the copper disk produced

magnetic fields that opposed tbe relative motions of diskand needle.

Most of this scries of experiments had required the short

space of only a few days, and in a few weeks Faraday had apretty complete notion of the processes of electromagneticinduction. His first paper on the subject was delivercd to

the Royal Society on November 24, 1031, entitled “Experi-mental Researches in Electricity.” New of the discoverpcaused a tremendous reaçtion t h r o u g h o u t tbe world. Theway now lay open Cor the conversion of meçhanical energyinto electrical energy, but the production of practical ma-

chines, by means of which this much-desired end was 10 be

açcomplished, still lay in the future.

OTHER CONTRIBUTIONS BY FARADAY‘The discovery of electromagnetic induction was one of the

greatest discoverics of all timc in its effcct 011 the materialwelfare and progrcss o f mankind. Faraday’s work i n elec-

60 Chapter Four

tricity did not, however, end here, for he made great stridesin electrochemistry, determined the specific inductivecapacities of many materials, established a relationship be-tween light and magnetism, investigated diamagnetism, andwith the assistance of his friend, the Reverend W. Whewell,established an important part of our present-day electricalnomenclature. Faraday brought into common use the fol-lowing terms:

electrode ion diamagneticanodecathode

electrolyteelectrolysis

anioncationlines of forceparamagnetic

dielectricelectrochemicalequivalentspecific induc-tive capacity

Berzelius must be considered the father of electrochemis-try, and although Davy made many great new discoveriesin this field, it was Faraday who established it as an exact,quantitative science. He developed the theory of ionizationand discovered the relationships from which he determinedthe electrochemical equivalents of a large number of ele-ments.

Faraday gave up his private practice about the year 1832.He had accumulated some money, and his needs were rela-tively simple. He did, however, continue to serve the Britishgovernment in many ways. He became a lecturer at theWoolwich Royal Military Academy in 1829 and continuedin this capacity until 1849. For a number of years he was aconsultant to Trinity House on lighthouses, and in 1847 heproposed lighting buoys with incandescent lamps using plat-inum spiral filaments.

No other man contributed SO much to electrical science asdid Faraday, and his achievements were recognized during

his lifetime hy many learned societies and universities inmany countries. He was humble, kindly, deeply religious,

quiet, persevering, and had almost an intuitive insight intonrany of nature‘s secrets, and beheld the wonders of crea-

tion with a reverent awc. His life ended in 1867.

JOSEPH HENRY

There is an amazing similarity between Faraday’s IXe andworks and those of his American contemporary, Joseph

Henry. The two rnen were very rnuch alike in many re-spects . Henry ws horn at Albany, IVew York, either on

Decemher 17, 17Yî: or 17YY, probably the latter. The cor,-fusion is due to the fact that the record in the old registerat Albany is not very distinct. He was of Scottish ancestry.

At an early age he went to live with his materna1 grand-

mother at Galway in Saratoga County where Ire attendedthe district school. At the age of ten hc began working halldays at a store in thc village and attended school only part-

lime. While he was still at Galway, hc gainrd accç~s to a

library in the village church, and as a result hc became apassionate reader.

At the age of fifteen, Joseph left Galway and returned to

his mother’s house in Albany. His father had died someycars earlier, and I us mother supporte<1 hcrself and her SO,,

by keeping boarders. For a lime, aîter his retwu to Alban)-,it seemed that Joseph might bccome an actor. Ile had CO~I-

siderable talents in acting, in arranging scenery, and in plny-writing, but his interests were srrddenly shiftcd in another

direction. At the agc of sixteen, hc wos confined tu thehouse for B bricf period due to an accident. While he was SO

confined, he happened upon a book belonging to a gentle-man who was then a boarder nt his mother’s house. The

book was entitled Lectures on Experimental Philosophy,

62 Chapter Four

Astronomy, and Chemistry by Dr. Gregory. This book SO

fascinated Young Henry that he resolved, forthwith, todevote his life to serious study.

Upon his recovery, Joseph Henry appeared before theother members of “The Rostrum,” a dramatic organizationof which he was then president, and tendered his resigna-tion. His next step was to enter a night school, whose facili-ties he soon exhausted. He then took up English grammarand rhetoric with a private teacher. These studies were fol-lowed by a brief period of tutoring, after which he enteredAlbany Academy as an advanced pupil. In order to meet hisexpenses, he began teaching in a neighboring school. Nexthe became an assistant at the Academy, and a little later heaccepted a position in the family of S. Van Rensselaer as aprivate tutor. While he was in the Van Rensselaer house-hold, he had much leisure time, which he devoted to studiesin the subjects which interested him most.

He was at this time considering preparing himself for themedical profession, but it happened that he was offered aposition as a surveyor with a party engaged in laying out anew road in southern New York, and he accepted the offer.A few months later, after the survey had been completed,Henry was offered a professorship at Albany Academy,which offer he quickly accepted.

HENRY’!3 FIRST EXCURSIONS INTO SCIENCEThe great series of electrical experiments and discoveriesthat soon brought fame to Joseph Henry began here atAlbany Academy. For an American city of that periodAlbany was well suited to the development of scientificpursuits, because there were several societies whose purposewas to promote scientific experiments and discussion.

Dr. Beck, who was president of Albany Institute, which

was one of these organizations, presented a series of lec-tures on chernistry, at whicb he was assisted by tlenry.Unfortunatcly Henry’s duties a s a p r o f e s s o r occupied SOmuch of his time that he had little leisorr for experiment.His teaçhing r e q u i r e d seven hours o f each d a y , elevenmonths of the year.

Henry’s rarliest scientifiç papers dealt with the adiabaticexpansion of steam aod with tbe cooling effects produçedby the expansion of gases. At this time, he was also assistingin compiling meteorological data for the Albany area.

Ilis first electrical paper, delivered before the AlbanyAcademy on October 10, 1827, dealt with the subject ofelectronlagnetisrn, and in this paper be described an electro-magnet made by William Sturgeon of London in 1825.Ilenry described this magnet as borscshoe shaped, woundwith a single widety spaced layer of eightecn turns of wireover a wrnish-insulated iron tore. With a powerful batterythis magnet WBS capable of lifting 0 pounds. Sturgeon’smagnet was the fi& to employ an iron tore. Ampère sndArago in France had made helices that behaved like mag-nets in 1820 and 1821. Jobann Sçhweigger of Halle, Ger-many, aided by J.C. Yoggendorff, built their so-callcd multi-plier in 1820, in which çlosely spaced coils of wire insulatedwith fabric werc wound upon a nonmagnetic spool.

By combining the ideas associated with tbe Sturgeon eleç-tromagnet and thç Schweigger multiplier, Ilenry began thçconstruction of clectromagoets in which he was the first tou s e superirnposed coils o f insolated wire, wound uponh o r s e s h o e - s h a p r d iron cores. Tbe insulation, wbich wasapplied by hand, was cotton or silk. For a later electromag-net it was said that Henry used a silk dress belonging to biswife. In 1820, be demonstrated an electromagnet using400 torns of wire with a lifting power of many pounds, but

64 Chapter Four

the exact figure is not known nor is the power of his bat-tery. Later in the same year he completed another magnet,with a %-inch iron tore wound with several coils. He be-lieved it was necessary to distribute the magnetizing forcealong t h e tore. Because his electromagnets had coils withmany turns, he called them intensity magnets. This lattermagnet, with a small battery, supported a weight of39 pounds.

HENRY PROPOSES

THE ELECTROMAGNETIC TELEGRAPH

After constructing a number of electromagnets, Henry be-came interested in operating an electromagnet at a distance.In 1830 he connected one to the end of a line 1030 feetlong and was able to operate it successfully from the otherend. Henry pointed out that it was possible to construct atelegraph in this way.

With the aid of P. Ten Eyck, he next built an electromag-net with a tore weighing 21 pounds, wound with nine coils,each of which contained 60 feet of wire, insulated withwaxed cotton. This magnet supported 750 pounds. In 1831at Yale College Henry supervised the making of an electro-magnet that supported 2065 pounds.

ELECTROMAGNETIC INDUCTION

Unlike Faraday, Henry did not keep a notebook to recordhis ideas and experiments, nor did he Write many papers atthis period of his life. In a later paper he mentions anexperiment, which he conducted in the early 183Os, inwhich he discovered independently the principle of electro-magnetic induction, but Henry credited Faraday with thediscovery. The apparatus used by Henry consisted of aniron bar in the middle of which was a coi1 connected to a

galvanometer. He placed t h e iron bar carrying t h e coilacross the poles of an electromagnet connected to a batteryand found that when he raised and lowered the plates ofthe battery into and out of the electrolyte, the galva-nometer needle was deflected, first in one direction andthen in the other.

SELF-INDUCTIONMile Faraday deserves the credit for the discovery of elec-tromagnetic induction, it was Henry who first discoveredself-induction. Self-induction is that property of an eleçtri-cal circuit that causes a counter electromotive force whenthe circuit is made or broken and is designated by thesymbol L. A little later, Faraday discovered self-inductionindependently. Henry was honored in the use of his namefor the unit of self-induction.

MARRIAGE AND PROFESSORWIP AT PRINCETONHenry had now become famous, but he remained a poorprofessor, and while money matters were of little concernto him, the lack of money undoubtedly hampered him inhis experimental pursuits. Despite his poverty and the im-probability that he could ever hope to earn a comfortableliving, he had married Ilarriet L. Alexander, his cousin, in1830. The mariage appears to bave been a happy ont inwhich six children were born to them, three of whorn sur-vived Henry.

Near the end of the year 1832, Henry was offered thechair of Natural Yhilosophy at Princeton Univcrsity, whichhe promptly accepted. As was the case at Albany, his teach-ing duties were arduous and afforded him little Lime forexperiment. In addition to his regular courses, whicb iomodem terms would probably b e called physics, h e also

66 Chapter Four

taught chemistry, minerology, geology, astronomy, andarchitecture. His burdens of pedagogy notwithstanding, hefound time to construct another magnet with a liftingpower of 1 Yz tons. He also installed a telegraph signal, in-cluding a relay, between the college and his house, a dis-tance of about a mile, using the earth as one side of thecircuit.

During what were rather happy years for him in the aca-demie surroundings of Princeton University, he continuedhis experiments in electromagnetism, electromagnetic in-duction, and self-induction. He was loved and revered byhis students and was regarded as perhaps the foremostscientist in his field in America.

In 1837, the university sought to reward Henry in somemeasure for the extraordinary services he had rendered,both to the university and to the world at large. He wasgranted a one-year leave of absence to visit Europe, onwhich visit he was accompanied by A. D. Bache, a descen-dant of Benjamin Franklin. Henry was received with greatcourtesy by European scientists, including Faraday, Wheat-stone, Daniell, Arago, and de La Rive. He was also invitedto speak before gatherings of the learned societies.

ELECTRICAL OSCILLATIONS AND

ELECTROMAGNETIC WAVES

Refreshed by his sojourn in Europe, Henry returned to hispost at Princeton and to his experiments. I-le had discoveredthe essential principles of the transformer and experi-mented with coils placed at varying distances from eachother. He also discovered the oscillatory nature of the dis-charge of a Leyden jar by discharging one across a gapthrough a circuit containing a small coil. In this coi1 he

placed an unmagnetized steel needle and found that afterdischarging the Leyde” jar the needle was magnetized,sometimes in one direction, and again in the opposite direc-tion.

This small coil and needle became very important in otherexperiments, as for example in detecting the inductive ef-fects of lightning, whiçh Ire accomplished by connecting thecoil between the met4 roof of his houx and the ground.Lightning flashes up to 20 miles away caused the needle tobe magnetized.

In a somewhat similar expcriment, he made a discoverywhose grc‘eat importance was not recognized until fifty yearslater. For this experiment, nenry strung a circuit of wireabout the pcrimrter of the uppcr floor of a building, and asimilar closed c i r cu i t , containing t h e çoil and needle ,around the walls of the çellar. The two circuits were about30 feet apart. When a Leyden jar was discharged throughthe circuit on the upper floor, he found that the needle inthe coil in the cellar had bcen magnetizcd. Frorn his dc-scription of this experiment it is clear that Henry recog-nizcd that h e w’as dealing w i t h a phcnomenor~ differentfrom thc electromagnetic induction erperiments, in whichthe coils were close together and connected by magneticcircuits contnining iron. He compared the effects in thepresent expcriment with those of light and spoke of thedisturhance being propagated wave-fashion.

OTHER RESEARCHES

\Vhile still a professor at Princeton, Henry carried on re-searches in many other fields, notably in meteorology, butalso in metallurgy, ballistics, light, and astronomy. The con-genial atmosphere at Princeton held Henry for fifteen years.

68 Chapter Four

THE SMITHSONIAN INSTITUTIONIn the year 1837 the United States government received abequest of about $500,000 from the estate of JamesSmithson, an Englishman, for the purpose of founding “atWashington, under the name of the Smithsonian Institution,an establishment for the increase and diffusion of knowledgeamong men.” For ten years the bequest was tossed about inCongress, but an organization was formed and a board of re-gents appointed. After SO many years of deliberation theboard of regents, in 1847, asked Joseph Henry to becomethe director of the Smithsonian Institution and to under-take its organization.

The founding of the Smithsonian Institution brings up avery interesting parallel. The Royal Institution in Londonwas founded in 1799, and the moving spirit in its foundingwas Benjamin Thompson (Count Rumford), an Americanby birth, who had a most colorful career in Austria, En-gland, and France. It was he who first appointed SirHumphry Davy as the head of the Royal Institution. TheSmithsonian Institution was founded by an Englishman,but it was Joseph Henry who gave it purpose and direction.

The offer of the regents was accepted by Henry, where-upon he resigned his professorship at Princeton and movedto Washington. He presented an outline of his conceptionof the organization and purposes of the Institution whichthe regents accepted. For thirty-two years Henry guided theSmithsonian Institution, writing, administering, planning,and experimenting. Under Henry’s administration, theoriginal bequest was not, as might have been expected, dis-sipated but rather increased to more than double its originalvalue.

Despite the great burden of administrative duties con-nected with the directorship, Henry found time to carry on

Figure 4.2 Joseph Henry (t’rom Smithsonim Institution)

70 Chapter Four

experiments of the most varied kinds, including acoustics,strength of materials, testing of munitions, advising onmilitary inventions, operation of lighthouses, foghorns, col-lecting meteorological and astronomical data, and manyother things. Henry’s well-filled life ended at Washington,D.C., on May 13, 1878.

5

Direct-CurrentDynamos and Motors

After the discoveries of Oersted, Faraday, and Henry in

electromagnetism, electromagnetic i n d u c t i o n , a n d self-induction, all of the necessary fac& needed for the develop-

ment of tbr generation of electricity by meçhanical meanswere known, but the construction of actual, practical ma-

chines still required the solution of many problems. Tbepurely researçh a s p e c t s o f elcctricity were now blending

inlo engineeriog problems.

PIXII’S MACHINEThe first small machine was built in 1832 by Hypolite Pixii

of Paris, an instrument rnaker who had become interestedin eleçtriçity. This machine was, in modem terms, a mag-

neto and consisted o f two coils o u a U - s h a p c d tore, thc

polc faces of which werr opposite the poles of a revolvingpermanent magnet. In its original form the machine pro-duçed alternating çurrent, but Pixii also built machines in

whiçh the coils revolved and whiçh were equipped withcommutators. In the samc year, Dal Negro, an Italian, builta similar magneto clcctric machine independently of Pixii.

Many others became interested in building small magnetomachines over the next eighteen years, including Sax~on of

Philadelphia in 1833, K. M. Clarke of England in 1834, and

Page of Washington in 1835. I)uring tbis period, there wereprobably vast numbers of other suçh machines built byunknown scient&, professors, mechanics, and others.

NOLI.E’T’S MACIIINESThe first improvement, after Piaii’s machine, was made by

II. hollet, a proSessor of physics in the military school at

72 Chapter Five

Figure 5.1 Pixii’s Machine and Clarke’s Machine. Pixiïs machinefor generating an electric current had a rotating magnet that inducedalternating magnetic fields in the soft iron cores and an electriccurrent in the coils that surrounded them. The current reversedtwice per revolution but was converted to direct current by a com-mutator. Clarke’s machine employed the same principle but hadrotating coils and a fixed magnet. (Courtesy Burndy Library)

Brussels. With the aid of his assistant, Joseph Van Malderen,he built a large machine in which thirty-two permanentmagnets were mounted on a stationary frame in longitu-dinal rows, spaced at equal angular distances. The rotorwithin this frame consisted of a number of coils equal tothe number of pole faces of the permanent magnets on thestator.

The magnet poles were, of course, arranged SO that theywere alternately north and south, and the coils were con-

nected in such a mariner that tbe induced electromotiveforces became additivc. The terminal wires were connectedto insulated rings mounted on the shaft, which had brushesbearing upon them in much thc same manner as later alter-nating-curent machines. AL 400 rcvolutions per minute thismachine produced 6400 alternations per minute, or 53l/3cycles. Because voltage hod not yet beerr defined, the pres-sure is not known, but since a similar macbine was usedlater for arc lights, we may assume tbat it was in the vicin-ity of 50 volts or perhaps a littlc more.The exact date of Nollet’s machine is indefinite, but it was

probably about 1849 or 1850. In 1853 a company wasorganized in Paris for the purpose of manufacturing ma-chines on the Nollet design. This company, called the Alli-ance Company, was probably the first electrical manufac-turing concern in the world. It produced several sizes ofmachines, having from thirty-two to forty-eight magnets,and from sixty-four to ninety-six coils. Originalty the Alli-ance machines were to be used for electrochemical workand, what now seems stranger still, for the decompositionof water to obtain oxygen and hydrogen for use with thclimelight or calcium light. For this purpose thc machineswere equipped with commutators. Unfortunately, the useof the machine for tbe decomposition of water was a busi-ness faiturr.

F. H. Holmes, of Engtand, adapted the Alliance machine toarc ligbting, using carbon points. Motive power was fur-nished by a steam engine, and it was found that it required5 horsepower t o supply t h e electrical energy f o r one1100.candlepower arc lamp. This and similar machines weresoon put to work in several British lighthouses and Faradayhimself directed the fint installation at South Forelandin 1858.

74 Chapter F i v e

DYNAMOS

In 1845 Wheatstone suggested the use of electromagnets inplace of permanent magnets for the fields of the new ma-chines, and similar suggestions came from Soren Hjorth ofDenmark and Varley of England. The first such machinewas built by H. Wilde of Manchester. It was not self-exciting, but instead it was equipped with a small magnetoused as an exciter. This arrangement was eminently success-fui, S O much S O that the machine overheated because ofoverload and also because of eddy-current losses in the solidiron cores of the armature and field magnets.

Wilde’s machine employed the shuttle armature, whichhad been invented a short time previously by Dr. WernerSiemens of Berlin. The success of this machine was fol-lowed shortly by the construction of self-exciting machinesat almost the same time hy Moses G. Farmer of Salem,Massachusetts, Alfred Varley and Charles Wheatstone ofEngland, and Dr. Werner Siemens of Berlin. These werecalled dynamoelectric machines, or simply dynamos, ascontrasted with the magnetoelectric machines, or magnetos.

Antonio Pacinotti of Florence, Italy, developed a slottedring armature in 1860, which was the prot.otype of mostlater machines. Lénobe Théophile Gramme of Belgium,who had been a patternmaker for the Alliance Company, in1871 constructed a ring armature, in which the coils werewound on a smooth iron ring. Although the Gramme arrna-ture was a more recent development, it was later abandonedin favor of the Pacinotti type.

ELECTRIC MOTORS

Many experimenters had sought to convert electrical intornechanical energy or, in other words, had sought to buildan electric motor. Several such devices bave been men-

tioned previously in this work, such as tbe whirligigs ofmilson and Hamilton, Franklin’s electric wheel, Barlow’s

w h e e l , and Faraday% revolving c o n d u c t o r , b u t none o ftbese was of any practical value.

In 3832 Sturgeon buill a small electric motor of a generaltype, of which there were many variations, in whicb con-

t a c t i s m a d e at regular inlervals ta energize a n electro-rnagnet, causing it to attract a revolving iron bar as it ap-proaches ~bc rnagnet’s polcs. Ilenry b u i l t n walking-bearnmotor on this principle. The mosl notewortby a t tempt of

this kind was made by Thomas LIavenport, a blacksmitb ofBrandon, Vermont, in 1834. He built such a motor power-

fui enougb to operate a small electric railway, and in 11140he opcrated a printing press witb tbe power supplied by one

of his motors.Professor Jacobi of St. Petersburg built a somwhat similar

motor in 1834, and in 1839, witb tbe use of such a motor,

propelled n b o a t carrying fourtren passcngers. 4 Scotch-rnan, Robert Davidson, in 1838 built an electric car weigh-

ing 6 t o n s . Tbere wete witbout doubt bundreds o f otber

similar attcmpts, but until tbr last quarter of the nineteentbcentury tbere were two serious draw-backs: there ~8s as yet

no satisfactory motor, and there was no cbeap source of

eleetric power.In lUi3, at au iudustrial exposition in Vicnna, there oc-

curred one of tbose fortunate accidents that profouodlyaffccted tbc c o u r s e o f rlectrical developmcnt. At tbe ex-

posi t ion WEIR an exhibit of Gramme dynamoelectric ma-chines. Khilc one of the machines was in operation, a work-mm carelessly cormected tbe terminaIs oSanotbcr macbineto tlx Ares that carried the electrical energy froc the firstIllachine. Tbe second machine began to whir nud spark at

the coturuutntor and attaincd :I cor~siderable speed before it

76 Chapter Five

could be disconnected. When Gramme was informed of thisstartling event, he grasped its importance immediately. Thenews was carried to the world through the technical jour-nals of the day and created a great stir.

Within the next decade the electric motor had been putinto service in many applications for which a compactsource of power requiring little attention was desirable suchas railways, elevators, mine hoists, machine tools, printingpresses, fans, sewing machines, and grinders.

6

Improvements in Batteriesand Electrostatic Machines

The development of the electric dynamo and motor oc-cur red during a p e r i o d wben there were rnany irnprove-mcnts in oldcr kinds of electrical devices. The fietd of etec-trical researcb hod broadened grcatty, and no si& line ofinquiry ~a.3 any longer sufficientty important to rnerit thcentire attention of electrical experimenters.

During tbe period under consideration many new forms ofvoltaic cetls appcared. In tbe lïrst tbirty years after Volta,practically att batteries KCX simple copper ond zinc couplesin an acid solution. Volta himself bad compiled a list ofelements, known a s the clectromotive series; wbicb i n -dicated tbc electricnt pressures that coutd be developed be-tween various couples. Sinee Volta bad no meauuring instru-ments worthy of tllc name, such an arrangement was anachievement of gcnius.

The original coppcr, zinc, aad acid batteries had severalserious faolts, cbicf among \rhicb was polarization, w b i c bhas been rnentioned previousty. Because of this defect, itwas impossible to draw a large current froc a battery formore tban a few seconds beforc its power was seriouslyimpairzd. The zinc and acid in tbese batteries werc ratberquickty consumcd and were expensive; aIso: the acid cauacdmuch damage when it \V~S spitted.

THE DANIELL CELL

Despite att of tbese objectionable cbaracteristics, tbere WBSno substantial change in batteries wtil 1836, when P r o -fesser .]. F. Danielt devised the battery tbat bears bis name.Tbis buttery still bad electrodes of copper and zinc, but tbesolution, now çattcd etectrotytc (Faraday’s term), ru-as cop-

78 Chapter Six

per sulfate and zinc sulfate. The zinc electrode was in aporous cup, in a zinc sulfate solution, and the copper elec-trode in cylindrical form surrounding the cup was immersedin a copper sulfate solution, a11 of which was contained in acylindrical glass jar. This battery did not polarize and usedneutral salts that were only mildly corrosive, and it was notexpensive. It delivered about 1.1 volts as we measure elec-tromotive force today. A modification of the Daniel1 cell,known as the gravity, crowfoot, or bluestone battery, waswidely used on American telegraph lines for many years. Inthis battery, the two fluids were separated from each otherby the difference in their specific gravities. The zinc sulfate,being lighter, floated above the copper sulphate. In its usualform the zinc, or negative, element was a heavy casting withradiating fingers (hence the name crowfoot) which wasclamped over the top of the battery jar by a lug oppositethe fingers. The copper element was made up of three orfive copper leaves, held together by a copper rivet in thetenter, with the outer leaves bent outward in arcs to form asomewhat star-shaped figure. The copper element was laidon the bottom, immersed in the copper sulfate solution,and was connected to the outside by means of an insulatedcopper wire that ran up the side of the jar and was bentover the edge.

In another modification of the Daniel1 cell, devised byJ. H. Meidinger, a spherical glass flask with a long neck wasfilled with copper sulfate solution, with the neck immersedin the part of the Daniel1 ce11 outside the porous cup. Whena battery of any of these types was in operation, copperfrom the copper sulfate solution was deposited on the cop-per electrode, while at the same time the zinc element wasconverted into zinc sulfate by chemical action of the freeSO4 ions, released by the copper sulfate, attacking the zinc

electrodc. The cffect was t o incrcasc tbe quantity o f z incsulfate and diminisb the quantity of copper sulfate; andtberefore, as the battery operated, some of tbe zinc sulfateso lu t ion had to he removed from t i m e t o time, and tbecopper sulfate replenisbcd. In the Meidingcr battery thiswas accomplished by means of the flask, and in the gravitybattery copper sulfate crystals were placed in the bottom,zinc sulfate drawn off, and the watcr replenished.

THE GROVE CELLSir W. K. Grave, in 1839, devised a çell in which a zincelectrode was placed in a porous cup in a dilute sulfuricacid solution, and outside tbe cup was a platinum plate inconçentrated nitric acid. The Grave battery had a highelectromotive force, about 1.9 volts, and it did not polarize,but it n’as objectionable because it gave off disagreeablebrown fumes produced by nitric acid, and the strong acidswere highly corrosive. Furthermore the platinum electrodewas very expensive.Bunsen altered the Grave cell somewhat in 1842 by sub-

stituting a carbon rod fo r t he p l a t i num element. Th ischange reduced the cost, but tbe otber objections to theGrave b a t t e r y still remained. The Bunsen cell was, never-theless, used rather extensively. Its voltage was the same asthe Crove battery, about 1.9.

THE LECLANCHÉ CELLThe most widely used batteries wcre those invented byGeorges Leclanché, whicb were known by that name. Theelements in tbe Leclanché battery werc zinc and carbon inan electrolyte of ammonium cbloride (sa1 ammoniac). Theearlier forms, called wet batteries, were made with a largecarbon cylinder, in t h e çenter o f which ~ILS a z inc rod

8 0 Chapter Six

separated from the carbon by an insulator. These batteriespolarized rather quickly, but this fault was partially over-corne by making the carbon electrode large and porous SO

as to absorb and distribute the hydrogen that appeared onthe positive electrode.

A later form of the Leclanché ce11 was the dry battery,which was widely used in telephone work and for rnanyothcr purposes, especially flashlights. In its usual form, thedry ce11 consists of a zinc container, which is also the nega-tive electrode, the inside of which is lined with paper andfilled with a mixture of granulated carbon and manganesedioxide saturated with ammonium chloride, with a carbonelectrode in the tenter. More recent dry cells have a steeljacket on the outside to prevent damage by efflorescence.Polarization is minimized by the manganese dioxide, whichgives up oxygen to form water with the hydrogen.

OTHER BATTERIES

There were numerous other forms of batteries which wereused at various times. Among these were the Fuller, Krüger,Lalande-Chaperon, Partz, Grenet, bichromate, and Smee.The Edison-Lalande battery is somewhat similar to theLalande-Chaperon b a t t e r y except t h a t i n t h e Edison-Lalande battery the positive electrode is copper oxide in-stead of iron, but the electrolyte in both cases is a solutionof caustic potash. The Edison-Lalande battery was ratherwidely used in the United States for railway signal work,because, among other reasons, the battery did not freeze.

Two standard cells have been introduced for use in thelaboratory. One of these is the Weston ce11 which has elec-trodes of cadmium and mercury and an electrolyte ofcadmium sulfate. Its voltage is 1.0183 at 20” Celsius. Theother is the Clark ce11 with electrodes of zinc and mercury

and an electrolyte of zinc sulfate. lts voltage is 1.4328 at

15” Celsius.In recent years several types of dry cells have been pro-

duccd in quantitics because of their special uses. ‘Thcy havc

such advantages as geater discharge capacities and longerlife; in some cases they are rechargeable. These batteries arenot necessarily new.

There is a rnercury battery that has a potassium hydroxideelectrolyte. The nickel-cadmium battery is rechargeable.Another rechargeable battery is the manganese-zinc battery

with a potassium-hydroxide electrolyte. If çompletely dis-charged this battery is ruined. Otherwise it may be charged

up to about f i f ty times. The silver cbloride battery dates

back to 1860 and is still used for special purposes.

%ORAGE BATTERIES

The principle of the secondary, or storage, hattery was dis-covered early, but for many years was of only scientific

interest because there was nothing to be gained by chargingone hat tery with another; the si tuation changed greatly

when the dynamo appeared. Gaston Planté, who had been

investigating polarization, made the very important dis-covery in 1860 that lead plates imrnersed in a sulfuric acid

solution and charged constituted an excellent secondarybattery. When such a battery was charged, a thin layer of

lead dioxide was formed on the posit ive plate, while the

negativc plate was converted into sponge lead. Planté’s hat-teries were forrned by repcated charging and discharging, a

process that was slow and expensivc. In his enrlier batterieshe rolled together two sheets of lead, separated hy heavylinen, gutta-percha, or ruhher. Later he constructed hat-teries with multiple Clat Plates in which the positive and

82 Chapter Six

negative elements were interleaved, as in a modern storagebattery.

Inspired by Planté’s successes, others began to experimentwith secondary batteries, notably Camille Faure, also aFrenchman, who in 1881, patented a battery with leadplates to which had been applied a coating of red lead. Thered lead was more easily converted to lead dioxide andsponge lead than the pure lead in Planté5 battery. TheFaure battery also had more active material and hencegreater capacity.

A further improvement was made by Sellon and by

Volckmar, who prepared the plates with grooved or per-forated faces, and the depressions were then filled with redlead paste before the forming process. Batteries of thistype, with further improvements, were built by Swan inEngland and Brush in the United States. Another improve-ment that followed shortly was the use of cast grids con-taining a small yuantity of antimony.

ELECTROSTATIC INDUCTION MACHINES

Electrical currents of considerable magnitude were nowavailable from batteries, magnetos, and dynamos, but therewas still great interest in the older electrostatic machines.There were many of the old frictional machines in use forexperimental purposes in laboratories, but Volta’s electro-phorus and Bennet’s doubler had shown that an originalsmall charge could be increased many times by manipula-tion. Holtz and Toepler in Germany and Wimshurst in En-gland devised new electrical machines based on the induc-tion principle, SO arranged that after a few turns a smallinitial charge was increased to a very large one. In thesemachines, as well as in an earlier one by C. F. Varley, sec-tors of metal foi1 were mounted on glass disks, which

in turn were mounted on shafts SO that they could be

revolved. Charges were built up by induction from disks ona neighboring plate. In the H&z and Toepler machine, the

second disk was stationary, whereas in the Wimshurst nn-chine the plates revolved in opposite directions.

These new electrostatic machines were built in great num-

b e r s f o r experimental purposes and also f o r t h e medicalprofession, 10 be used for the treatment of disease. Vol-u m e s were written o n the subjecl o f eleçtrotherapeutics,

and eleclrodes of ail conceivable shapes were designed toreach the various organs or tissues to be treated. no pro-gressive or prosperous physician’s office was w i t h o u t aHoltz or Wimshurst machine and a multitude of accessories.Some of these machines were of grcat sice, and they per-

formed miracles, if the reports of the period could be be-

lieved, but miracles notwithstanding the machines graduallydisappearcd from the physiçians’ offices.

We may douht thc testimon& regarding thc alleviation of

human suffering, but these machines did çontrihute i n avery substantial way to the inçrease of knowledge and af-

forded muçh cntcrtainment. One of the most beautiful ex-

pcriments thal could be performed with such a machinewas with Geisslcr tubes. Heinrich C;e&ler was a glassblower

at tbe university at Bonu, Germany. His tubes were made in

many fantastic shapes; some were evacuated, while otherscontaincd traces of various gases or mercury. Many of thr

g l a s s eovelopes çontained mctalliç salts that fluoresçedwhen excited by the electrical machine. In some respects,

Geissler tubes anticipated modem tube or fluorescent light-ing.

During thc early part of this period, tbe most important

developrnent was t h e introductiou o f t h e eleçtromagnetic

telegraph, but this is a story in ilself and Will be told later.

84 Chapter Six

The electric bel1 was the first electrical device to be usedextensively in homes. The inventor of the electric bel1 is notdefinitely known, but it may have been Miraud of Rouen,France, or his compatriot Leclanché, the inventor of thesal-ammoniac battery.

Before the large-scale commercial use of electricity forlighting, there were electrical concerns manufacturing tele-graph instruments, insulated wire, table, batteries, in-sulators, bells, and many telegraph accessories. These con-cerns were often instrumental in the development of newapparatus such as annunciators, burglar alarms, fire alarms,and railway signals. As the scope of the industry widened,several of these firms took over the manufacture ofdynamos, lighting equipment, switches, sockets, fixtures,fuses, and a hundred other items. Some of these companiesbecame the nuclei of the great electrical manufacturing con-cerns of today.

7

Electrical Instruments,La~s, and

Definitions of Units

~More electriçity could beçome an exact science, capable

of mathematical analysis, it was essential that its propertiesbe defined in terms of measurable units. Certain conceptsregardirrg electrical power, pressures, quantit ics, rates offlow, and those relating to circuits, such as reaistance, self-

induction, capacity, and still others relating ta dielectricsand chernical action had already been well established be-fore the units of measurenrent were defined. Similar ideas

regarding magnetism and magnetic circuits existed.

TANGENT GALVANOMETERA great many instruments of various kirlds bave already

been mentioned in previous chapters, some of whicb were

nrere indicators, and others provided accurate quantitativemeasurements. A great improvement in the Scbweigger and

Poggendorff multiplier was made by Pouillet in 1837, atwbich time he invented the tangent galvanometer. This iw

strument h a d a relatively large coi1 w i t h a diamcter o f30 centimeters or more, at the centcr of whicb was a short

magnetic needle to which a pointer was attached at rigbtangles that moved over a scale divided into degrees. Whenno current flowed through thç coil, the needte came to restin the magnetic meridian, but when a current was sent

through tbe coi!, witb the plane of the toit in tbc magot-ticmeridian, the needle took a position which was in the direc-tion of tbe resultant of tbe forces produced by tbe eartb’smagnetic field and the field produced by the carrent flow-

ing through the coil. By reading the deflection of the needle

in degrees, the current could be calcutated by multiplying

86 Chapter Seven

Figure 7.1 Poutilet’s Tangent Galvanometer (Courtesy BurndyLibrary)

Electrical Instruments and Laws 87

the constant for the particular instrument by the tangent ofthe angle of deflection. Weber greatly improved this instru-ment in 1846 by attaching a small mirror to the needle, inwhich the reflections of a scale could be read through atelescope. In the same year Weber also built a moving coi1galvanometer, as opposed to the stationary coi1 in the tan-gent galvanometer. This instrument depended only on theinteraction between the field produced by the coi1 and theearth’s field.

D’ARSONVAL GALVANOMETER

The most reliable of a11 galvanometers was that invented byDeprez and d’Arsonva1 in 1862, known as the d’Arsonva1galvanometer. In this instrument a small moving coi1 wassuspended between the poles of a permanent magnet. Themagnet was provided with concave pole faces. A cylindricaliron tore was mounted between the pole faces, leaving agap on either side sufficient for the coi1 to swing withouttouching. Originally the coi1 was suspended on torsion wiresthat were also lead-in wires for the coil. Later the coi1 wasmounted on jeweled bearings with hairsprings used as arestraining force and also used as conductors for the cur-rent.

WHEATSTONE BRIDGE

Wheatstone’s bridge, as it is commonly known, althoughaccording to Silvanus P. Thompson, it was invented byChristie, came into use about 1843. It was the first accuratedevice for comparing resistances. In it an unknown resis-tance could be inserted into a divided circuit that includedthree known resistances, a battery, and a galvanometer.When the known resistances, one of which was variable,were properly balanced SO that the galvanometer reading

88 Chapter Seven

was zero, the unknown resistance could be calculated by asimple proportion.

ELECTRICAL AND MAGNETIC LAWSThe advent of accurate measuring instruments made it pos-sible to verify and extend electrical and magnetic laws thatin many cases had been proposed on the basis of partialinformation. Some of these laws have already been men-tioned, such as the inverse square laws for electric and mag-netic fields by Coulomb, the law governing the force be-tween a conductor carrying a current and a magnetic poleby Ampère, and Ohm’s law, which was announced in apaper in 1827, entitled “Die Galvanische Kette.”

Before units of measurement for electricity and mag-netism could be established, it was necessary to define cer-tain fundamental relationships by laws expressed in theform of equations. It is regrettable that we do not know theauthors or the years for some of these laws, particularly themagnetic laws, but it is probable that many if not a11 ofthem were the work of Gauss. Between the years 1820 and1862 electrical and magnetic laws, measurements, and unitswere firmly established through the efforts of a long list ofworkers including Ampére, Coulomb, Biot, Savart, Faraday,Henry, Ohm, Poisson, Pouillet, Gauss, Weber, Lenz, Rie-mann, Kirchhoff, Neumann, Kohlrausch, Green, Joule,Lord Kelvin, von Helmholtz, and Maxwell.

The accomplishments of these men were greatly in-fluenced by the work of Newton as set forth in hisPrincipia. Newton was the first scientist to apply mathe-matics to such general natural laws. Newton had establishedthe inverse square law for gravitational fields, althoughHooke had claimed credit for the principle. Coulomb WZLS

undoubtedly aided by this law for gravitational fields in

Electrical Instruments and Laws 89

Table 7.1. FundamentaI Equations

ElectricEquation Author Year

f = k gq’/? Coulomb 1785

H = 2i/r Biot and 1820Savart

f = im . ds/r2 Ampère 1822q = it - -

I = V/R Ohm 1827V = d@/dt Faraday 1831Heat = ki2Rt Joule 1843

MagneticEquation Author Year

f = k mm’/r2 Coulomb 1785

H = 4nnill - -

H= 2nnilr - -

H=f/m - -

@=BA - -

p=B/H - -

formulating his law for electric and magnetic fields, whichhe confirmed by means of his torsion balance.

Table 7.1 gives the fundamental electric and magneticequations upon which the definitions of units were based.

ELECTRIC AND MAGNETIC UNITSKarl Friedrich Gauss (1777-1855) and Wilhelm Weber(1804- 1891) were the principal authors of the electric andmagnetic units. Gauss developed a system of magnetic unitsin 1832, using the millimeter, milligram, and second as theunits of length, mass, and time. In 1839 Gauss definedelectric potential at a given point in the electrostatic systemas the work required to move a unit charge from infinity tothat point. Beginning in 1840, Weber developed the defini-tions of the electric units in the electromagnetic system. Healso, as did Gauss, used the millimeter, milligram, secondsystem. Other scientists generally preferred the centimeter,gram, second system, or, as it is generally known, the cgssystem.

90 Chapter Seven

For some years after Gauss and Weber there were nowidely accepted units for electricity and magnetism. In1861 the Committee on Electrical Standards of the BritishAssociation for the Advancement of Science, under theleadership of William Thomson (later Lord Kelvin), wasgiven the task of formulating definitions that would be con-sistent with one another and would be reproducible. Theyrecognized the work already accomplished by Gauss andWeber and proceeded from that point. In the committee’sreport of 1864 it established values for the practical unitsof electromotive force and resistance, based upon themeter, gram, second system. This committee established thepractical unit of electromotive force, which it called thevolt, at lO* times the absolute electromagnetic unit. Thepractical unit of resistance, which this committee called theohm, was established at 109 times the emu absolute unit.From these definitions of the volt and ohm the practicalunit of current would become l/le the emu absolute unit.

A later committee of the British Association recom-mended in 1873 the use of the cgs system instead of themgs system. This committee also recommended the use ofthe terms erg and dyne for the absolute units of work andforce. These recommendations met with general approvalthroughout the scientific world.The first International Electrical Congress met in Paris in

1881 and approved the cgs system as the basis for thedefinitions of the electric and magnetic units. The ParisInternational Congress confirmed the definitions estab-lished by the British Association in 1864 and 1873. It alsodefined and named the coulomb and farad.

Neither the British Association nor the International Con-gress gave any consideration to the esu absolute system ofunits. Gauss and Weber had developed both the emu and

Electrical Instruments and Laws 93

Table 7.2 shows the ratios of the principal practical elec-trie units to the emu and esu absolute units. Table 7.3 is acorresponding table for magnetic units.

It is somewhat ambiguous to speak of practical magneticunits since the emu units are used in most practical applica-tions.

The subject of electric and magnetic units is rather confus-ing SO that in reading a textbook one must first discoverwhich system of units the author is using. Systems other

Table 7.2. Practical Electrical Units

Kind of Name of patios of Practical Units to

Unit U n i t Symbol emu esu

Potential Volt Y 108 1/(3 x 102)

Current Ampere I 10-l 3 x 109

Resistance O h m R 109 1/(9 x 10”)

Quan t i t y C o u l o m b 0 10-l 3 x 109

Capacity Farad C 1o-g 9 x 10”Self-Induction Henry L 109 1/(9 x 10”)

Table 7.3. Practical Magnetic Units

Kind ofU n i t

M.M.F.FluxReluctance

In tens i tyPermeability

Induction

Name of Ratios of Practical Units to

U n i t Symbol emu esu

Gilbert 5 1 3 x 10’0Maxwell @ 1 l/( 3 x 10’0)Gilbert aMaxwell 1 9 x 1020

Oersted H 1 3 x 10’0G a u s sOersted ’ 1 149 x 1020)

Gauss B 1 1/(3 x 10’0)

92 Chapter Seven

esu absolute electric and magnetic units. Weber noted thenumerical ratio between the two systems in 1846. In 1856Weber and Kohlrausch found that the dimensions of thisratio constituted a velocity which equaled the velocity oflight, within the limits of experimental error. The velocityof light was known approximately at that time from theobservations of Roemer in 1676 on the eclipses of Jupiter’ssatellites. The first accurate, terrestrial measurements weremade by Fizeau in 1849.

The fourth International Electrical Congress met at theWorld’s Fair in Chicago in 1893. It confirmed the previousdefinitions of the absolute and practical units and defined aprototype of the standard ohm as the resistance of a col-umn of mercury 106.3 centimeters in length, and 1 squaremillimeter in cross section at a temperature of 0” Celsius.The prototype of the volt was given in terms of the voltageof the Clark standard ce11 whose voltage was given as1.434 volts at O°Celsius.There were periodic meetings of the International Electri-

cal Congress at which refinements in the definitions werediscussed but in general the original absolute and practicalunits remained unchanged. Suggestions were made fromtime to time for modifications in the definitions of theunits. In 1882 Heaviside suggested changing the definitionof the unit magnetic pole SO as to eliminate the factor 4~that occurs in certain of the fundamental equations. Fopplin 1894 proposed changes in the coefficients of the funda-mental magnetic and electric units for the sake of greatersymmetry. Lorentz called this the Gaussian system. Giorgiin 1901 proposed a combination of these suggestions withthe mks (meter, kilogram, second) system. These and otherproposals Will be discussed later.

Electrical Instruments and Laws 91

Figure 7.2 Lord Kelvin (From Bumdy Library)

94 Chapter Seven

than the practical, emu, or esu which have been introducedare the following: mks (meter-kilogram-second), mksa(meter-kilogram-second-ampere), Giorgi (Same as mksa),Heaviside-Lorentz (rationalized system that suppresses thefactor, 47~), and Gaussian (electric units numerically equalto esu and magnetic units equal to emu).

The IEC (International Electrotechnical Commission),which was organized in 1904, is now an arm of UNESCO inthe field of electrical engineering. It and its committees arenow responsible for the definitions of electric and magneticunits. In 1935 the EMMU committee of the IEC adoptedthe mks system, and in 1950 the U. S. Congress passed alaw fixing the electric units for the United States as definedin the mksa system.

The subject of electric and magnetic units has now be-corne SO involved that it would be impossible to discuss thematter fully in this history. Volumes have been written onthis subject, but the best and most concise review of thepresent state of the matter is U. S. Bureau of StandardsMonograph 56 written by the late Francis B. Silsbee, pub-lished in 1962, and reprinted in 1963.

8

The Electric Telegraph

The need for rapid communication between distant pointshas been felt from the beginnings of civilization. Many earlymethods were devised, some of which operated with afair degree of success and are still in use. Among thesedevices are semaphores, smoke signals, drums, the firing ofcannon, heliographs, blinker lights, bells, and others. In thetime of Pierre de Maricourt it was proposed to use compassneedles for signaling, on the theory that the movement ofone compass needle would cause a similar movement inanother needle, even at a great distance. Magnetic needlesdid in fact become part of certain telegraphic devices at alater date.

After Stephen Gray’s discovery of the transmission ofelectricity over conducting threads and the experimentsthat followed, in which Leyden jars were discharged overgreat lengths of wire, the thoughts of many turned to theuse of electricity for communication. Gray’s experimentswere made in 1729, and in 1746 Winckler set up an electrictelegraph in which there were as many wires as there werecharacters to be transmitted.

Scots Magazine published in 1753 an anonymous letter,later ascribed to Charles Morrison, which proposed usingmany wires each of which would terminate in a metal bal1corresponding with a letter of the alphabet. Near each bal1was to be hung a strip of paper, properly labeled, whichwould be attracted when a charge was sent over the line. Healso suggested the use of glass insulators for supporting thewires.

Lomond proposed in 1787 using a single wire with a pithbal1 electroscope at the receiving end and, presumably,using some sort of code. Reizen built a multiple-wire tele-

96 Cha@r Eight

graph in 1794 in which sparks at the receiving end wereused to identify the characters transmitted. Sommeringbuilt a multiple-wire telegraph at Munich in 1809, usingVolta’s recently discovered batteries and Carlisle andNicholson’s discovery of the decomposition of water. Eachof the wires in Sommering’s telegraph terminated in a cupof acidulated water, SO that when the circuit was closed,through the battery, bubbles of gas were liberated in theappropriate cell.

EARLY ELECTROMAGNETIC TELEGRAPHSAfter Oersted’s discovery of electromagnetism and Schweig-ger’s invention of his galvanometer or multiplier, bothAmpère and Laplace proposed electromagnetic telegraphsemploying coils and magnetic needles at the receiving end,equal in number to the cliaracters to be transmitted, with acorresponding number of wires. Harrison Gray Dyar built atelegraph line on Long Island, New York, which operatedduring the years 1828 and 1829, in which messages wererecorded on a moving strip of paper by electrochemicalmeans.Joseph Henry’s line, built in 1830, has already been men-

tioned. On this line he used the equivalent of a telegraphsounder. Weber and Gauss built a telegraph line atGottingen in 1833, which was nearly a mile in length, inwhich the receiving device was a galvanometer. In the sameyear Baron Schilling constructed a telegraph line at St.Petersburg, using five needles in his receiving apparatus.

Wheatstone’s telegraph of 1837 employed a single needleand was the first to be used commercially. A considerableamount of telegraph business developed in England duringthe ensuing years. In 1837 Steinheil constructed a telegraphline at Munich, more than 12 kilometers in length, using a

The Electric Telegraph 97

receiving apparatus that recorded the message on a papertape by means of dots. Steinheil also discovered in 1838that it was possible to use the earth for one side of thecircuit.

SAMUEL F. B. MORSEMany others were giving serious thought to the problem ofthe electric telegraph, among whom was Samuel F. B.Morse (1791-I872), who had acquired a limited scientificknowledge during h i s undergradua te days a t Ya leUniversity. At this time, however, Morse was far more inter-ested in painting than in science, and to this end he spentthe years 1811 to 1815 in England studying art. Upon hisreturn to the United States he became a successful portraitpainter, and in 1825 was one of the founders of the Na-tional Academy of Design. His interest in science was re-vived in 1827 when he studied electromagnetism underJ. F. Dana of Columbia College. He was still, however, in-terested primarily in painting and in 1829 returned toEurope to study the great works of art in the galleries ofEngland, France, and Italy.

On his return voyage to the United States aboard thepacket ship Sully, he met Dr. Charles S. Jackson, who de-scribed to Morse a number of electrical experiments he hadwitnessed a short time before in Paris. These conversationswith Dr. Jackson renewed Morse’s interest in electromag-netism, whereupon he confided to Dr. Jackson his latentideas about an electric telegraph. He soon became com-pletely absorbed in the matter to the extent that he couldthink of nothing else. He worked out in considerable detailthe design of an electromagnetic telegraph recorder, amechanical sending device, a code of dots and dashes fornumbers, and perhaps also a relay.

The Electric Telegraph 99

Before the Sully reached port, Morse had made rathercomplete sketches and notes on the recording telegraph heintended to construct. The Sully docked at the wharf at thefoot of Rector Street in New York on November 15, 1832.As he disembarked, Morse was met by his two brothers,Sidney E. and Richard C. Morse. Because he was almostwithout funds at the time, his brother Richard invited himto live at his house until such time as he might again be-corne self-supporting. Morse’s brothers were the publishersof a newspaper, the New York Observer, and were appar-ently comfortably well-off.The telegraph that Morse had in mind at this time was

designed to send and receive by mechanical means. In hissending apparatus he planned to use a form of type consist-ing of dots and dashes. He was given a room at his brother’shouse where he began immediately to work on his tele-graph. Here he cast type and in the process damaged thefurniture and carpets. His brother then gave him the use ofa room of the fifth floor of the newspaper building, at thecorner of Nassau and Beekman Streets. This room becamehis shop, studio, kitchen, living room, and bedroom. Herehe worked, ate, slept, and lived in the direst poverty. It isnot clear how his three children were cared for. They hadbeen living with relatives since the death of their mothersome years earlier.

Morse labored on his telegraph in these quarters for sometime and then moved to Greenwich Lane. Here he eked outa bare living by painting an occasional portrait and by giv-ing lessons, but his primary concern was with his telegraph,which began to take shape in a very crude form. His trans-mitting instrument was made with a wood frame on whichwas mounted a pair of wooden rollers, one of which wasprovided with a crank. A belt made of carpet binding

100 Chapter Eight

passed over the rollers and carried the portrule, a sort oftypesetter’s stick, in which the lead type was placed. Alever was mounted above the rollers on a pivot near itstenter, one end of which was provided with a roundedtooth that engaged the projections on the type as theportrule was carried forward. At the other end of the lever,a wire bent into the form of an arc was attached with itsends dipping into two mercury cups.

The receiving apparatus of this first Morse telegraph wasalso built on a wood frame. It carried three wooden rollers,over which passed a strip of paper. One roller was driven byclockwork that moved the paper strip lengthwise. Over themiddle roller was a pendulum whose swing was limited bytwo stops. On its lower end, it carried a pencil that wasmade to move crosswise of the paper strip under the in-fluence of an electromagnet. The circuit passed from onepole of the battery through the mercury cups, to the line,to the electromagnet and returned to the battery over theother side of the line. Impulses corresponding to the dotsand dashes, set up in type on the portrule, were sentthrough the circuit, causing the pendulum to swing andcausing the pencil at the lower end of the pendulum todraw an irregular sawtooth line. The mark on the papercould then be translated into dots and dashes and, bymeans of the code, into numbers. Morse’s code at this timewas not alphabetical but contained only numbers, whichcould be translated into words by means of a dictionary.

In 1835 Morse was appointed professor of the Literatureof the Arts of Design at New York City University, and wasassigned to quarters in the university building on Washing-ton Square. He moved his belongings to the new quarters,including, of course, his telegraph.

Progress up to this time had been painfully slow, but

The Electric Telegraph 101

within a short time, perhaps with the help of ProfessorPage, he succeeded in getting his telegraph to operate, andlate in 1835 was able to exhibit his invention to a group offriends. Professor Page was Charles Grafton Page, a nativeof Salem, Massachusetts, and a physician turned physicistand inventor. He contributed greatly to the development ofthe induction coil. He built several motors of the inter-mittent impulse type, one of which he used to operate asmall locomotive. He was also the author of several bookson induction.

In 1836 Morse continued his work on the telegraph inorder to improve its operation. He also experimented withrecording by chemical means, a method that had previouslybeen carried out by Dyar, and later by Bain, but Morsedecided against it. Also during this period, Morse gavefurther thought to the matter of relays and in 1835 or 1836designed such a device.

DEMONSTRATION OFTHE FIRST MORSE TELEGRAPH

On Saturday, September 2, 1837, Morse exhibited his tele-graph, operating over 1700 feet of wire, to a group whichincluded Professor Daubeny of Oxford University, Profes-sor L. D. Gale of New York City University, ProfessorTorrey, and Mr. Alfred Vail, who was a recent graduate ofthe university and whose family owned the Speedwell IronWorks of Speedwell, New Jersey. The Vail business in-cluded a brass and iron foundry and a machine shop.

PARTNERSHIP WITH ALFRED VAILAlfred Vail became greatly interested in Morse’s telegraph,and returned the following week to discuss the inventionmore fully with Morse. He was convinced that the telegraph

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was practical and entered into a partnership agreement withMorse under which the Speedwell Iron Works would under-take the construction of an improved instrument. This ar-rangement was vital to the success of the telegraph andresulted in the production of much better and more reliableinstruments.

U. S. GOVERNMENT INTERESTED IN TELEGRAPHOn March 10, 1837, the secretary of the treasury, LeviWoodbury issued a circular letter to collectors of customs,commanders of revenue cutters, and other interested per-sons regarding a resolution passed by the House of Repre-sentatives, which requested information on a system of tele-graphs for the government of the United States. Morse, whohad received a copy of the circular letter, sent a detaileddescription of his telegraph and its mode of operation tothe secretary, dated September 27, 1837, and on Novem-ber 28, 1837 sent a second letter giving the secretary theresults of the demonstration at New York City Universityin September.

The Speedwell Iron Works was in the process of making animproved Morse telegraph, which was completed late in1837 and was demonstrated in a room at the Speedwellshop on January 6, 1838, over a 3-mile circuit of insulatedcopper wire. It is not clear whether the new instrumentused a fountain pen or merely a stylus to indent the paper,but both methods were used in Morse telegraph instru-ments. The new receiving instrument made four separatelines of dots and dashes on the paper, probably on thetheory that at least one would be legible. The code in usewas still the early one, using only numbers that were trans-lated into words by means of a specially prepared dic-tionary .

The Electric Telegraph 103

DEMONSTRATIONS OF THE IMPROVED

MORSE TELEGRAPHThe telegraph was now ready for a public demonstration,and such a demonstration was held before a large gatheringin the Geological Cabinet of the University of the City ofNew York on January 24, 1838. Ten miles of wire wereused in this test, and for the first time what is now knownas the Morse code was employed. In other words, messageswere composed of characters representing letters and notnumbers. There is some evidence to indicate that Vailrather than Morse may have been responsible for this newtelegraphic alphabet, although Morse was undoubtedly con-sulted in the matter. Whether or not the portrule formechanical sending was still in use at this time cannot bedetermined definitely. Vail had improved the Morse tele-graph greatly and had t ransformed it from a crude workingmode1 to an instrument that in appearance and per-formance was of commercial quality.

A more important demonstration was given on Feb-ruary 8, 1838, before the Franklin Institute of Philadelphia,perhaps the foremost scientific body in the United States atthe time. Its Science and Arts Committee was greatly im-pressed by what it saw.

From Philadelphia, Morse took his telegraph to Washing-ton, where on February 21, 1838, President Van Buren andhis cabinet witnessed the transmission of telegraphicmessages over 10 miles of wire. Preceding this demon-stration, Morse had written a letter to F. 0. J. Smith, chair-man of the Committee on Commerce of the House ofRepresentatives, in which he proposed building an under-ground line 100 miles long and offered the telegraph for thesole use of the government because he foresaw a possiblemisuse of the facility in private hands. After the demonstra-

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tion, Morse, in a second letter, reduced the suggested dis-tance to 50 miles and requested an appropriation of$26,000, excluding contingencies, to finance the construc-tion of an experimental line.

Following Morse’s letter to Smith, the Commerce Com-mittee reported to the House of Representatives on thedemonstration and recommended an appropriation of$30,000. Mr. Smith then decided that he would like to jointhe telegraph venture and offered to resign his position inCongress. A partnership was agreed upon between Morseand his associates in which sixteen shares were divided asfollows: Morse nine shares, Smith four shares, Vail twoshares, and Professor Gale one share.

PATENT APPLICATIONS

On April 7, 1838, Morse applied for a United States patent.The partners believed that foreign rights to the inventionshould be protected by patents as well as the rights athome, and accordingly Morse and Smith sailed for Englandon May 16, 1838. After spending seven weeks of frustratingeffort with British officiais, they were refused a patent,partly on the grounds that a telegraph had already beenpatented by Wheatstone and Cooke, and partly because theclaim was made that the details of Morse’s telegraph hadalready been published. Both arguments appear to havebeen insincere, and the truth was probably that the Britishgovernment did not wish to have an American firm invadethe British telegraph business. Although Morse was greatlydisappointed in his efforts to obtain a British patent, hefound pleasure in being able to attend the coronation ofEngland’s great Queen Victoria as the guest of the Ameri-cari minister, Andrew Stevenson.

Morse and Smith left England on July 26, 1838, on theirway to Paris. In Paris Morse exhibited his telegraph to a

The Electric Telegraph 105

distinguished gathering which included Arago, Baron Hum-boldt, Gay-Lussac, and others. In describing the apparatusexhibited in Paris, Morse again referred to the portrule,indicating that he had still not given up the idea of mechan-ical sending.

Morse remained in Paris until March of the following year,during which time he exhibited his apparatus to manygroups and individuals. There was at this time much politi-cal unrest in France involving King Louis Philippe, and as aresult the patent application was delayed. He did, however,receive a patent eventually, but it had little value because ofcertain oddities in the French patent law, which providedthat an actual installation must be made within two years.Since the telegraph was to be a government monopoly, andsince the French government was not disposed to make thenecessary expenditures, nothing came of the patent.

While in Paris, Morse made application for a Russianpatent through the Russian minister, Baron Meyendorf.Shortly thereafter, he returned to England and held furtherdemonstrations before members of the House of Lords, af-ter which he sailed back to the United States aboard thesteamer Great Western, which arrived in New York onApril 15, 1839.

Because Morse and his partners lacked funds and becauseCongress had not acted on the bill providing money forbuilding an experimental line, there was little progress dur-ing the next several years. After more than two years aUnited States patent was issued to Morse on his telegraphon June 20, 1840. The delay was not SO much the fault ofthe patent office as it was Morse’s failure to supply a11 ofthe necessary information. There was no action by Con-gress on the appropriation bill during the sessions of 1840,1841, and 1842.

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SUBMARINE CABLEDuring this rather dismal period for Morse and his partnersthere was one interesting new development. Morse some-how got together enough money to have two miles of sub-marine table manufactured, which he laid between the Bat-tery and Governor’s Island in New York harbor in thesummer of 1842. A test of this table was made on Oc-tober 19, 1842, during which four characters were receivedwhen transmission was suddenly interrupted. A ship’sanchor had fouled the table, and when it was drawn to thesurface the ship’s crew tut it off because they had no ideaas to its purpose. This table contained a single strand ofcopper wire, insulated with rubber and protected withspiral strands of tarred hemp.

CONGRE% APPROPRIATES $30,000

FOR AN EXPERIMENTAL LINEOn December 30, 1842, Charles G. Ferris, a member of theCommerce Committee of the House of Representatives,submitted a report on Morse’s telegraph together with a billcalling for the appropriation of $30,000 for the construc-tion of a telegraph line by Samuel F. B. Morse and his as-sociates. This bill passed the House on February 23, 1843,by a vote of eighty-nine to eighty-three. The Senate waspreoccupied with many matters, but finally on the last dayof the session, Marc11 3, 1843, just before midnight, the billwas approved by the Senate without opposition. Morse hadbeen sitting in the gallery a11 day and into the evening,hoping that the telegraph bill would be called up. When hewas told that there was no likelihood that the bill would beconsidered, he left the Senate Chamber with a heavy heart.He was informed of its passage early the next morning by

The Electric Telegraph 107

Miss Ellsworth, the daughter of the commissioner of pat-ents, who had become a friend of Morse.

CONSTRUCTION OF THE LINEMorse and his partners were jubilant and began immedi-ately to make preparations for the construction of a tele-graph line between Washington and Baltimore, to be laidunderground in lead pipe. Vail began the manufacture ofnew telegraph instruments. Professor L. D. Gale was put incharge of construction. Professor J. C. Fisher supervised themanufacture of the insulated wire, and Ezra Cornell, whohad invented a machine for laying pipes underground, wasput in charge of laying the lead pipe.

It became evident after some miles of pipe had been laidthat the underground system would not work. Apparentlythe difficulty lay in the fact that the joints in the pipe werebeing made with the insulated wire in place, and the heatused in splicing charred the insulating material and caused itto break down. The lead pipe was probably in short lengths,and no junction boxes were used.

Two-thirds of the appropriation had been spent when theunderground project was abandoned, but some of the ma-terials purchased could be salvaged. It was then decided toerect poles along the Baltimore and Ohio Railroad right-of-way. Morse referred to the poles as spars, and they weredescribed as 30 feet high, probably the overall length. Theywere placed at intervals of 200 to 300 feet, a distance whichwas too great for the small-sized copper wire used. The wirewas probably no larger than No. 14, and with these longspans there was difficulty later with the breaking of wiresand of wires swinging together in high winds. Sufficientwire had been purchased to span four times the distancebetween Baltimore and Washington, but it is unlikely that

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a11 of the wire was used. The wire was attached to in-sulators, but there is no description of them. Later it wasthe practice on American telegraph lines to use glass in-sulators, whereas on European lines porcelain was used.

In earlier experiments with the telegraph, Morse had usedCruikshank batteries, with which he experienced consider-able difficulty because of polarization, but on this projecthe turned to the Grove battery, which was expensive butdid not polarize. On his latest European trip Morse hadlearned of the Daniel1 cell, which he admired greatly butwhich for some unknown reason he did not use on this line.Later a modification of the Daniel1 cell, known as the grav-ity cell, became the American standard for telegraph use.

As the line progressed, constant testing was carried onfrom various points along the line to the terminal in Wash-ington. When the line reached the railway junction nearBaltimore, a temporary station was established from whichmessages could be exchanged with Washington. Work hadthen been in progress for about a year, and it was decidedthat the line must be in operation by May 1, 1844, at whichtime the National Whig Convention was to meet in Balti-more.

When Henry Clay was nominated for president by theConvention, the news was carried by messenger to theterminus of the then-existing line and sent to Washingtonby telegraph. Similarly, the nomination of TheodoreFrelinghuysen for vice-president was sent to Washington.Shortly thereafter the telegraph circuit was completed toMount Clare depot in Baltimore and to the Supreme Courtbuilding in Washington.

“WHAT HATH GOD WROUGHT!”

On May 24, 1844, the first officia1 test of the line was to bemade. On the morning of that day Morse, his friends, and

The Electric Telegraph 109

other observers gathered about the instrument in the Su-preme Court building in Washington while Alfred VaiI wasat the instrument in Baltimore. Morse had agreed to allowMiss Ellsworth to Select the message to be sent, as anacknowledgment of his gratitude for her service in bringinghim the news of the passage by the Senate of the appropria-tion bill. Miss Ellsworth chose a short passage from theBook of Numbers in the Bible, “What hath God wrought!”The message was sent by Morse and received by Vail inBaltimore, who promptly repeated the message back toWashington. Morse was congratulated by his friends andsoon by officia1 Washington as the news of his successspread.

It is impossible to say precisely how the operation wascarried out, but it seems clear that Morse had abandonedhis portrule and had changed to some form of key. In de-scribing a later test , Mr. Holmes of South Carolina, abrother of a representative in Congress, described the opera-tion in a room beneath the Senate Chamber in these words,“saw him operate by dipping into a phial of quicksilver theend of one wire from the battery.” This method of operat-ing was very crude, but with the aid of Alfred Vail thetelegraph key soon came into existence.After the first officia1 message on May 24, 1844, the

Washington instrument was moved to the lower level of theCapitol in readiness for messages from Baltimore in connec-tion with the Democratic National Convention, which as-sembled there on May 26, 1844. After nominating James K.Polk for president, the Convention nominated Silas Wright,a senator from New York for the vice-presidency. Mr.Wright was not present at the Convention but had remainedin Washington. When the news of his nomination was sentto Senator Wright by telegraph, he refused to accept it. His

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refusa1 was promptly sent back to Baltimore and an-nounced to the unbelieving delegates, who adjourned untilthe following morning in order to confirm the rejection, ifsuch was indeed the case. The telegraphic message was con-firmed by Senator Wright, and thereafter the messages be-tween Baltimore and Washington were given full credence.

COMMERCIAL OPERATION OF THE TELEGRAPHDuring the following year the telegraph operated withoutcharge to its users. Expenses were covered by an appropria-tion by Congress of $8000, and the telegraph was placedunder the supervision of the postmaster general. Alfred Vailbecame the operator at Washington, and H. J. Rogers atBaltimore. Beginning April 1, 1845, a charge was made ofone cent for each four characters transmitted, but therevenue was insufficient to caver the cost of operation.

Morse tried to interest the federal government in the con-struction of a telegraph line to New York, by way of Balti-more, Wilmington, Philadelphia, and Trenton, but he wasunsuccessful. He then organized the Magnetic TelegraphCompany, which was incorporated in Delaware on May 15,1845, by special act of the legislature. It was the purpose ofthis company to build the line to New York. Its stock-holders were Morse, Gale, Vail, Ezra Cornell, and twenty-three others.

On August 6, 1845, Morse again sailed for England, andagain failed in his patent application. From England hewent to Holland, where the Wheatstone telegraph was inuse but was now equipped with electromagnets. Morsenoted that on the line between Amsterdam and Haarlem,No. 12 iron wire was being used, which had a much greatertensile strength than the smaller copper wire on his Wash-ington-Baltimore line.

The Electric Telegraph II 1

From Holland Morse went to Hamburg by steamer andthen back to Paris, where he exhibited his telegraph beforethe French Chamber of Deputies on November 10,184s.

CONSTRUCTION OF NEW TELEGRAPH LINES

In 1846 Morse’s United States patent was reissued withimprovements up to that time. Telegraph lines were nowunder construction in many directions, and in June 1846the line between Washington and New York was completed.By 1847 a line was completed to St. Louis, and in 1848 onewas constructed to Louisville and Nashville. The latter linewas built by Henry O’Reilly and was soon involved in apatent suit brought by Morse, in which after some years oflitigation, Morse was upheld by the United States SupremeCourt. This was only one of many such suits that followed.

WESTERN UNIONBy 1851 there were over fifty telegraph companies in theUnited States. The Western Union Telegraph Company wasorganized originally as the New York and Mississippi ValleyPrinting Telegraph Company on April 1, 1851, for the pur-pose of building a line from Buffalo to St. Louis. This com-pany bought progressively the lines and equipment of othersmaller companies until after twenty years it had unifiedmost of the entire telegraph system of the country. Manyof the smaller telegraph companies had been in seriousfinancial difficulties and were more than willing to sel1 theirholdings to the larger and stronger Western Union.

PRINTING TELEGRAPHSThe original New York and Mississippi Valley TelegraphCompany did not use the Morse telegraph but rather theHouse Printing Telegraph System, which had been devel-oped by Royal E. House of Vermont. This system, unlike

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the Morse recorder, printed the message in plain letters andnumerals. Similar instruments using the so-called step-by-step method had been worked out by Cooke and Wheat-stone in England and improved by Stroh. These latter in-struments did not, however, print but merely showed theletters to the receiving operator, whereas House’s instru-ment printed the message on paper. The House system wasfirst used on lines between boston and New York and be-tween New York and Philadelphia. It continued in use oncertain lines until 1860 when it was replaced by the simplerMorse telegraph with key and sounder. The sounder wasfirst used in 1858, much to the chagrin of Morse himself,whose operators had learned to read the messages cominginto his recording machine by sound.

In later years one of the stock tickers was devised onsomewhat the same principle as the House printing tele-graph, but there were at least half a dozen stock tickersusing various schemes. The key and sounder remained thestandard on both American and European telegraphs formany years, but eventually the high-speed printer wasdeveloped and replaced the key and sounder altogether.

RELAYS, DUPLEX AND MULTIPLEX SYSTEMSMany auxiliary devices and improvements were produced asthe telegraph business grew. The relay, which Morse hadinvented at an early stage, was greatly improved and wasmade very sensitive. In order to reduce the capital invest-ment in lines, ways were sought to increase the capacity ofthe lines by speeding up the rate at which messages couldbe sent and by sending simultaneous messages over thesame circuit. Gintl of Vienna was the first to invent aduplex telegraph in which a message could be sent in each

T h e Electric Telegraph 113

direction at the same time. This telegraph came in 1853,and was followed the next year by other duplex telegraphsby Frischen, and Siemens and Halske. None of these wasvery successful, and it was not until 1871 that J. B. Stearnsinvented a successful telegraph of this type. Many othershad worked on the problem including Stark, Edlund,Preece, Nedden, Farmer, Maron, and Muirhead.

In 1874 Edison invented his quadruplex telegraph, whichmade possible the sending of two simultaneous messages ineach direction over the same circuit. The first multiplexsystem was invented by M. G. Farmer of Salem, Massachu-setts, in 1852, using a commutation method, but this devicewas not used until many years later, probably because ofthe difficulty in maintaining synchronism at the two endsof the line. A similar device was exhibited by Meyer at theVienna Exposition in 1873. Harmonie telegraphs usingtuning forks were invented by Elisha Gray, Edison, andBell.

RAILWAY TELEGRAPHS

It is interesting to note that the development of the tele-graph and of the railroads took place at about the sametime. In England the Wheatstone telegraph was used fortrain dispatching very early, probably before 1840. OnAmerican railways the use of the telegraph for this purposedid not occur until somewhat later, although Morse’s firstline was built on a railroad right-of-way and the Baltimoreinstrument was in a railway station. Many of the later tele-graph lines were also built along railway lines, and the tele-graph office was often in the railway station. The railwaytelegraphs were usually independent of the commercial tele-graphs.

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THE FIRST TRANSCONTINENTAL TELEGRAPH LINEThe New York and Mississippi Valley Telegraph Companychanged its name to Western Union Telegraph Company onApril 7, 1856. Its telegraph lines were spreading across thecontinent at an amazing rate. On October 24, 1861, thefirst transcontinental line was in service, an event which wasof great importance to the federal government, because theCivil War was then in progress. It was almost eight yearslater, on May 10, 1869, that the first transcontinental rail-way line was completed. During the Civil War the telegraphplayed an important role in many campaigns, and this wasthe first major war in which either the telegraph or therailroad was used.

ELECTRICAL MANUFACTURING

The telegraph was the first electrical industry, and itbrought with it the organization of numerous manufactur-ing concerns producing telegraph instruments, relays, linewire, insulated magnet wire, table, poles, cross arms, in-sulators, pins, lightning arrestors, linemen’s tools, and vari-ous other items. These industries grew to considerable size,and were in some cases the predecessors of companies thatlater produced dynamos, lighting equipment, and telephonesupplies.

9

The Atlantic Cable

EARLY SUBMARINE CABLESSubmarine tables were not new at the time the earliestattempts at laying an Atlantic table were made. Morse hadlaid a 2-mile submarine table in New York harbor in 1842.In 1845, between Fort Lee and New York City, Ezra Cor-ne11 laid a table 12 miles long, which contained two copperwires insulated with cotton and India rubber and protectedby a lead sheath. This table operated several months butwas destroyed by ice.

In 1849 a British company undertook the laying of a tele-graph table between Dover and Calais, but this table failedbecause the insulation consisted merely of tarred hemp,which could not withstand the penetration of seawater. Thefollowing year a new table insulated with gutta-percha wasmanufactured in England and was laid across the channel insix or seven hours by two small steamers. This table, how-ever, soon failed due to mechanical stress. Still anothertable was manufactured containing four wires, each insu-lated with gutta-percha and overlaid with hemp tordssoaked in tar and tallow and protected against abrasion byan iron wire armor. This table, laid in 1851, operated suc-cessfully.

In late May 1852, England and Ireland were connected bytable, and a yea r later t he re was a table be tweenScotland and Ireland. In June 1853 a telegraph table waslaid between Oxfordness in England and The Hague in Hol-land, a distance of 115 miles, the longest table SO far.

NEWFOUNDLAND CABLEAs early as 1849 or 1850, F. N. Gisborne, an English en-gineer who had previously been in charge of the construc-

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tion of telegraph lines in Nova Scotia and New Brunswick,proposed, to the Newfoundland House of Assembly, theconstruction of a telegraph line from St. John’s in New-foundland to the mainland. This line would cons& of over-land portions about 400 miles in length and an underseaportion of 85 miles. The route was to extend fromSt. John’s to Cape Ray, from Cape Ray to Cape Breton bysubmarine table, and across Cape Breton Island to themainland of Nova Scotia, where connections could be madewith existing telegraph lines.

When Gisborne surveyed the rugged terrain in Newfound-land, he decided that it would be necessary to put the lineunderground, and thereby also avoid the difficulties inmaintaining the line under adverse weather conditions. Ilehad been granted &500 by the Newfoundland House of As-sembly for the survey and raised sufficient funds fromother sources to begin construction. Ile had completed only30 to 40 miles of the line when his funds were tut off andconstruction was halted.

It was necessary to obtain new capital from other sources,and therefore, in 1854 he went to New York where he metMatthew D. Field, a civil engineer, who had been engaged inbuilding railroads and bridges. Field became interested andcalled in his brother Cyrus CV. Field, who had retired theprevious year from a successful business as a New Yorkmerchant and who, although only thirty-four years old, hadacquired a substantial fortune.

Cyrus Field invited Gisborne to his home to discuss thematter of the Newfoundland line, but Field soon had widervisions including a submarine table across the Atlantic. Hearranged a meeting with Samuel Morse, who had long cher-ished the notion that communication by telegraph underthe oceans was possible. In a letter to F. 0. J. Smith dated

The Atlantic Gable 117

March 2, 1839, written in Paris, Morse said, “1 see now thata11 physical obstacles which may for a while hinder, Willinevitahly be overcome; the problem is solved; man mayinstantly converse with his fellow man in any part of theworld.”

THE ATLANTIC CABLE

Both Field and Morse became enthusiastic over the possi-bility of establishing telegraphic communication with En-gland. Field set about raising the necessary capital immedi-ately. He organized a company of six partners called theNew York, Newfoundland, and London Telegraph Com-pany. The original partners were Cyrus Field, David DudleyField, an attorney and brother of Cyrus, Peter Cooper,Moses Taylor, M. 0. Roberts, and Chandler White. Later,after a charter had been granted by the NewfoundlandHouse of Assembly, the names of Samuel Morse, Robert W.Lowber, Wilson G. Hunt, and John W. Brett were added tothe list of partners. The new company acquired the Gis-borne properties.

In the fa11 of 1854, Field went to England to order tablefor the 85-mile Cabot Strait crossing, between Cape Rayand Cape Breton. When the Cabot Strait table was de-livered, it was loaded aboard a small sailing vesse1 that en-countered a severe storm and foundered, with the loss of a11of the table on board. A second attempt was successful,and the necessary land lines were completed, SO that by1856 communication was established between St. John’s inNewfoundland and New York.

The very difficult task of laying a table on the little-known ocean floor was now to begin. The first step was totake soundings to determine the most feasible route. Boththe British and the American governments were deeply

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interested in the project, and each authorized its navy toundertake soundings. For the British navy, LieutenantCommander Joseph Dayman was in charge, and for theUnited States Navy, Lieutenant Berryman. Berryman,sailing east, followed the great circle route out of TrinityBay, Newfoundland, and Dayman followed a westwardroute out of Valentia in Ireland. Both found the existenceof a great plateau, which received the name of TelegraphPlateau. The greatest depth encountered on the plateau was2400 fathoms, and there appeared to be no serious prob-lems in the way of laying a submarine table.

CABLE COMPANY IS ORGANIZEDOn September 26, 1856, the Atlantic Telegraph Companywas incorporated in England by Charles Bright, John Brett,and Cyrus Field, with an initial capital of &350,000. Thereis no further mention of Gisborne’s original company, theNewfoundland Electric Telegraph Company incorporated in1852, or the New York, Newfoundland, and London Tele-graph Company organized in 1854. It may be assumed thatthe useful assets of these companies were transferred to thenew company and that they were then dissolved. Gisborne’sname does not again appear in connection with the tablecompanies, but apparently he remained active in the Cana-dian telegraph business, for in 1879 he was appointed su-perintendent of the Canadian government telegraph andsignal service.

Field had left New York bound for England on July 19,1856, to arrange for the manufacture of table and to con-sult with his British partners regarding other steps thatmight be required for the table project. With the or-ganization of the new company, control passed fromAmerican to British hands, but this change was probably

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for the good of the undertaking because more British cap-ital was available, the table manufacturing companies werein England, and the British government was willing to sub-sidize the project with money and with ships. The UnitedStates Congress later also voted to render assistance.

CONTRACTS FOR THE MANUFACTURE OF CABLEEarly in 1857 the manufacture of 2500 miles of table wasbegun by two British firms, Glass Elliot and Company ofLondon and R. S. Newall and Company of Birkenhead,near Liverpool. The specifications for the table called for aconductor composed of seven strands of No. 22 copperwire covered by three layers of gutta-percha. This portionof the table was furnished by the Gutta-percha Company,after which it was sent to the two table companies. At thetable works the inner tore was wrapped with hemp tordthat had been treated with tar and other compounds. Next,the outer armor was applied which consisted of eighteen,seven-strand No. 22 iron wires. The outside diameter of thecompleted table was a little more than 5/s inch, and itweighed approximately 2000 pounds per mile. In additionto the submarine table, some 25 miles of land table for theshore ends were manufactured. This table was nine times theweight per mile of the main table, and was more heavilyarmored to protect against abrasion on the rocky shores.The main table had been made in 2-mile lengths that werelater spliced.

Technical consultants for the Atlantic Cable Company in-cluded William Thomson (later Lord Kelvin) of Glasgow,Michael Faraday, and Samuel Morse. The board of directorswas made up of the three organizers, Brett, Bright, andField, a number of British bankers and businessmen, andlater Lord Kelvin. Dr. Wildman Whitehouse, a doctor of

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medicine, whose interests had turned to electrical pursuits,was engaged by the company to take charge of testing andother technical matters, and unfortunately he was the supe-rior of the very able consultants who had far more knowl-edge of telegraph problems.

THE CABLE FLEET

The United States Navy assigned the steam frigate Niagaraof 5200 tons to the table-laying project, accompanied bythe side-wheeler Susquehanna, and the British navy fur-nished the Agamemnon of 3200 tons, accompanied by thepaddle-wheel steamer Leopard. Bot11 the Niagara and theAgamemnon had been specially equipped with tanks intheir holds for storing the table, and with table-laying ma-chinery o n t h e i r decks, including drums, guide wheels,brakes, dynamometers, and steam engines.

On April 21, 1857, the Niagara sailed from New Yorkwith Samuel Morse on board. Morse no longer had anyfinancial interest in the Atlantic table but had an intensepersona1 interest. After his arriva1 in England, Morse wentashore to renew old friendships.

LOADING AND TESTING THE CABLEThe manufacture of the table was completed in June, butloading aboard the two ships was not finished until lateJuly. The Agamemnon, because of its lighter draft, loadedits table at the Glass-Elliot works on the Thames, and theNiagara took its cargo aboard at the Newall works at Bir-kenhead, where there was deeper water.

Before going on to Valentia in Ireland, where table-layingwas to begin, the ships met in the quiet water of the Coveof Cork near Queenstown in order to make a final test ofthe table. Considering the fact that the table had been

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made in 2-mile lengths and spliced, such a test was verynecessary. It was this matter of splicing which probablyaccounted for much of the delay in loading. When the endsof the table aboard the two ships were joined and a batteryand galvanometer connected, it was found that the tablewas continuous and the insulation was good. The sluggishbehavior of a long table, due to its capacity, was alreadyknown and was confirmed by these tests, in which three-quarters of a second was required for a signal to traverse the2500 miles of table.

From the Cove of Cork the ships sailed toward Valentiaon the southwest toast of Ireland, where they arrived atthree o’clock on the afternoon of August 4, 1857. ByAugust 6 the land portion of the table had been placed andsecured.

LAYING THE CABLE

It was agreed that the Niagara would begin laying its table,and in mid-ocean a splice would be made with the table onthe Agamemnon, which would then continue the laying tothe Newfoundland terminus. The ships moved out on themorning of August 6, but after only 5 miles of table hadbeen laid it caught in the machinery on deck and snapped.The broken table end was retrieved in comparatively shal-low water and spliced. After a delay of less than a day theconvoy again moved westward toward Newfoundland.

During the laying, communication was maintained withthe station at Valentia in order to keep a constant check onthe condition of the table. At one point contact was lostfor a period of 2% heurs but then resumed. After movingwestward for two days, the ocean depth had reached2000 fathoms and the strain on the table had increasedproportionately, as this great length of table dangled into

The Atlantic Cable 123

the depths of the ocean. It was necessary to keep the table

taut as it passed over the sheave at the Stern of the ship, inorder to prevent the weight of the table alone from pullingit out SO rapidly as to deposit it in coils on the ocean floor.

Early in the morning of August 11, 1857, the engineer incharge of the drums that paid out the table found that itwas moving out too fast and applied the brake, whichgrabbed S O quickly that the table broke. At that time335 miles of table had been laid, and there was nothing tobe done but to return to England. Both ships put ashore atPlymouth and unloaded their table. At this time the tech-nique of grappling the table on the ocean floor had not yetbeen perfected, SO that in this instance the table alreadylaid was abandoned.

PROJECT POSTPONEDUNTIL THE FOLLOWING YEAR

Th ’e project was given up for the year 1857, but plans wereimmediately made to continue the project the followingyear. First of all, 700 miles of new table were ordered, andsubstantial improvements were made in the deck machineryfor paying out the table. At this time Thomson developedhis marine galvanometer that was to play such an importantrole in receiving table messages. With this device it waspossible to receive twenty words a minute, or ten times thenumber previously received. Thomson5 galvanometer wasvery sensitive and consisted of a delicately suspended,short, steel magnet, placed inside a coi1 of fine, insulated,copper wire. Just above the movable magnet, a small mirrorwas mounted which reflected a beam of light on a scaleplaced some distance in front of it. Behind the scale was alamp the light from which passed through a small openingin the scale to the mirror on the instrument. The reflected

124 Char)ter \tine

Figure 9.2 Thomson’s Marine Galvanometer (Courtesy BurndyLibrary)

spot of light from the lamp appeared on the scale where thedeflection could be read.

It was then decided that on the next attempt at laying thetable, the ships would meet in mid-ocean and proceed inopposite directions after making a splice. The wintermonths of 1857-1858 were devoted to fitting the ships withthe new deck machinery, improving the table tanks in theholds, instructing the crews, and in general making use ofexperience ah-eady gained.

The Atlantic Gable 125

SECOND ATTEMPT

In the spring of 1858, the ships arrived at Plymouth to takeaboard the table deposited there the previous year and inaddition the 700 miles of new table. Loading was com-pleted about the middle of May, and on May 29, 1858, theships sailed out of Plymouth harbor to the Bay of Biscay,where various experiments and tests were conducted intable-laying, buoying, and splicing. On June 3, 1858, theships returned to Plymouth harbor, and a week later sailedout for their mid-ocean rendezvous, where table-laying wasto begin. Besides the Niagara and the Agumemnon, the sup-porting vessels, the Vulorous and the Gorgon of the Britishnavy, made up the table-laying fleet.

By the time the vessels were out on the high seas thegreatest storm in the North Atlantic, in the memory of theexperienced seamen aboard the ships, broke upon the fourvessels. The high seas were particularly hazardous for theAgumemnon because she carried a deck load of table forwhich there was no room in the hold. After several days thestorm abated, and the ships proceeded to their rendezvouswithout serious damage. When the ships met in mid-oceanon June 25 the weather was calm and a11 was in readiness.

CABLE IS SPLICED IN MID-OCEAN

On the following day the tables on the two ships werespliced and the joint lowered into the sea. The ships nowmoved apart; the Agumemnon toward Ireland, and the

Niagara toward Newfoundland. After only 3 miles of tablehad been laid, the table on the Niagara caught in the deckmachinery and snapped. The ships returned to their startingpoint, spliced the table once again, and once more set outtoward their respective destinations. On June 27, whenthe ships were 80 miles apart, the circuit was interrupted by

126 Chapter Nine

what was found to be two breaks in the insulation. Oncemore the ships returned to the starting point, and again thetable was spliced. Al1 went well until June 29 when thetable broke about 20 feet from the Stern of the Agumem-non. About 300 miles of table was lost, but there still re-mained a sufficient length to complete the line between thetwo terminals. The table fleet turned back and arrived atQueenstown early in July, where the vessels were refueledand loaded with a new stock of provisions. On July 17 thefleet sailed out once again toward the mid-Atlantic. Splicingof the tables was completed on July 29, after which theships set out for Newfoundland and Ireland. This time onlyminor difficulties were encountered, and the table-layingwas completed on August 5 by both ships. When the newsof the successful table-landing was telegraphed to NewYork and from New York to a11 parts of the nation, cele-brations were held everywhere.

INSULATION BREAKS DOWNThis table continued to operate only until September 1,during which time less than four hundred messages hadbeen transmitted. Various explanations were offered for thefailure of the table. Undoubtedly the insulation had brokendown, and some held that the fault lay with the manufac-turers, some believed the insulation was injured by expo-sure to sun and weather while it was stored at Plymouth,and others attributed the damage to the fact that Dr. White-house, in testing, had applied high voltage from an induc-tion coi1 to the table.

The clouds of civil war were already hovering over theUnited States. Cyrus Field’s persona1 fortune was wiped outin a fire in 1859 and a business depression in 1860. In theinter im the Atlantic table management had learned muchfrom the failures, as had also the table manufacturers.

The Atlantic Gable 127

THE SECOND CABLENo further attempts were made to lay another table untilthe end of the Civil War in the United States. When workwas resumed in 1865, a single vesse1 was employed, theBritish-owned Great Eustern, the largest vesse1 in the world.The new table was much improved over those used in the1857 and 1858 attempts. Among other modifications theconductor was increased in size to seven strands of No. 18copper wire, with nearly three times the cross section of theearlier table conductors. Four layers of gutta-percha wereused instead of three, and the outer armor of stranded ironwires, of which there were ten, was covered with tarredhemp.

The Great Eastern was equipped with three iron-platetanks for storing the table and with much-improved paying-out machinery on deck. Below deck was an electrician’sroom in the charge of Mr. de Sauty, which was equippedwith batteries, Thomson’s marine galvanometer, clock, log-books, and such other paraphernalia as would be required.Among those on board to render technical assistance wereWilliam Thomson, C. F. Varley, and Cyrus Field.

MOST OF THE CABLE IS LAID SUCCESSFLJLLYBEFORE IT BREAKS

Early in July 1865 the table was loaded aboard the GrearEastern, which then proceeded to the new terminus about6 miles distant from the former landing place at Valentia.About 30 miles of shore table had already been placed bythe Caroline, and attached to a buoy in the harbor. Whenthe Great Eastern arrived, the splice was made to the shoretable, and on July 23 she and two accompanying warshipsof the British navy steamed out of the harbor toward theirdestination at St. John’s, Newfoundland. There were only

1 2 8 Chapter hine

minor difficulties until a point some 600 miles east of New-foundland had been reached. At that time a fault developedin the table after it had passed over the Stern of the ship,and an attempt was made to pull it back. As it was beingpulled back the table broke and efforts to retrieve it wereunavailing. Although the table had been grappled threetimes, in each case either the grappling table or some of itsattachments had failed. Further efforts to retrieve the tablewere abandoned and the ships returned to England.

There was of course great disappointment in the minds ofa11 who were connected with the project as well as in thegeneral public. Because of the many failures it became in-creasingly difficult to raise capital for the table enterprise.A new company called the Anglo-American Telegraph Com-pany was formed at this time, but it is not entirely clearwhether this company was a reorganization of the AtlanticTelegraph Company or merely a holding company to ar-range the necessary finances. In any case a new table wasordered and made ready. This table again differed some-what from the earlier ones in that it was stronger, and thearmor was made of galvanized wire.

THE THIRD CABLE

The new table was aboard the Great Eastern by the end ofJune 1866. Two additional ships, the Albany and the Med-way were chartered by the company to accompany theGreat Eastern. The Medway carried what was left of the1865 table in addition to 90 miles of heavier shore table. Itwas about July 12, 1866, after the shore table had beenlaid, that the convoy began its westward journey. Every-thing worked smoothly until the sixth day out when thetable became badly fouled in the after tank. The ship wasstopped quickly, and after several heurs the snarl was dis-

The Atlant ic Cable 129

entangled. No further mishaps occurred, and the table wassafely landed in a small inlet in Trinity Bay, where therewas a tiny village called Heart’s Content. The landing of thetable occurred on July 28, 1866, but the work of the ex-pedition was not yet finished. After a brief rest the shipsagain steamed out into the Atlantic to recover the end ofthe 1865 table, a task which was accomplished on Au-gust 31. A splice was made, and the second table wasbrought ashore on September 7. There were now two tablesin good operating condition.

Commercial service on the tables was begun soon after thefirst table was brought ashore, using the Thomson marinegalvanometer. Reading the messages received by this instru-ment was necessarily slow, because it depended entirely onobserving the deflections of the spot of light on the scale,to the right and to the left. At first the rate of transmissionwas only eight words per minute, but this rate soon in-creased to sixteen or seventeen. There was great need for arecording device, but the difficulty lay in the very feeblecurrents that could be transmitted over the table. In orderto trace a record of the message on paper a frictionless penwas needed.

THE SIPHON RECORDERIn 1867 Thomson, then Sir William Thomson, obtained apatent on what was called the siphon recorder, which was avery different instrument from his mirror galvanometer. In-stead of a stationary coil, a very light movable coi1 wassuspended by means of metallic torsion wires between thepoles of a strong permanent magnet. Connected to the coi1was a small glass siphon tube, one end of which dipped intoa bottle of ink and the other end, drawn out to a finecapillary tube, was held a short distance above a brass plate,

130 Chapter Rine

over which passed the paper strip on which the message wasrecorded.

The ink bottle was insulated and was kept charged by anelectrostatic machine. As the coi1 moved to and fro, underthe influence of the currents from the table, carrying withit the siphon tube, tiny drops of ink were deposited on thepaper in the form of a wavy line, pulled out by electrostaticattraction. The record was very similar to that in Morse’soriginal recording telegraph. There was nothing new in themoving coi1 principle since it had been applied earlier byWeber and d’Arsonva1. The siphon recorder with improve-ments and modifications became the standard receivingdevice for table messages, and was used for many years.

At first the charge for a message between New York andLondon was five dollars per Word, but as the speed of trans-mission increased and experience was gained in the opera-tion of the table, the cost was reduced until at the presenttime such a message costs in the neighborhood of twelve totwenty-three cents per Word, depending on the kind of ser-vice.

10

The Telephone

BOURSEUL AND REISIn the August 26, 1854, issue of L>Illustration of Paris thereappeared an article, written by Charles Bourseul, on theelectrical transmission of speech. Bourseul did not claimthat he had built an apparatus such as he described. The de-vice that he envisioned had a transmitter consisting of astretched membrane, to which was attached a metallic con-tact at its tenter. When the membrane was caused to vibrateby a sound, its contact would open and close a circuitthrougb a fixed contact in close proximity to the first. Thecircuit was completed through a battery and a receiver. Thereceiver consisted of an electromagnet whose poles werevery close to a thin iron diaphragm.

Johann Philipp Reis, professor of physics at Friedrichs-dorf, Germany, delivered a lecture in 1861 before thePhysical Society of Frankfurt in which he described an in-strument he had built, which he called the telephone, andwhich he said would reproduce sounds. Reis’s telephonewas essentially the same type of instrument described byBourseul except that the receiver was a knitting needle,wound with fine wire, and attached to a light wood box

which acted as a resonator. Reis himself said that he hadbeen unable to reproduce human speech sufficiently dis-tinctly to be intelligible. Others claimed that the instrumentwould transmit speech, and considered Reis the inventor ofthe telephone.

Reis and others who worked on this problem apparentlydid not realize that in order to reproduce speech it wasnecessary to do more than open and close a circuit veryrapidly, but rather that the electric current had to be modu-lated SO as to correspond as closely as possible with the

132 Chapter Ten

Figure 10.1 Reis’s Telephone (Courtesy Burndy Library)

complex wave form as well as the volume of the impressedsounds. Helmholtz had shown that the quality of a soundwas due to a combination of tones and not to a single puretone. The Reis transmitter was incapable of transmittingthe complex combination of tones that give the humanvoice or a musical instrument its quality. Furthermore, theReis instrument could not reproduce the variations in loud-ness. At best such a transmitter might reproduce a puretone, but more often the effect on the receiver was merelya rattle.

ALEXANDER GRAHAM BELL

It is generally acknowledged that Alexander Graham Bell(1847-1922) was the inventor of the telephone, but there

The Telephone 133

were numerous contributions by others. Bell was born inEdinburgh, Scotland, on March 3, 1%7, to Alexander Mel-ville Bell and his wife Eliza Grace (Symonds). Besides Alex-ander there were two brothers, Melville James, who wasolder, and Edward Charles, who was younger than Alex-ander.

The father had achieved recognition as a teacher of correc-tive speech and elocution, and also as a lecturer at theUniversity of Edinburgh and at New College. He and hisbrother published a book in 1860, called Z’he StandardElocutionist, which eventually ran through several hundrededitions.

Alexander and his two brothers received their early educa-tion from their mother, including lessons in music. At theage of ten Alexander entered a private school in Edinburgh,where he remained for a year, after which he attended theRoyal High School, from which he graduated at the age offourteen. After graduation Alexander spent a year with hisgrandfather in London, who taught him something of thegracious living of a gentleman and encouraged him in thestudy of speech and acoustics. Alexander, at this time, hadambitions to become a concert pianist, after having studiedthe piano in Edinburgh under the tutelage of Signor Au-guste Benoit Bertini, but his grandfather discouraged thisidea.

When he returned to Edinburgh, Alexander began a moreserious study of his father’s speech methods and particu-larly of the applications of Visible Speech, which was amethod of producing the various speech sounds by meansof ten basic symbols involving the positions of the tongueand lips. Combinations of these symbols could produce anyspeech sound in any language.

At the age of sixteen Alexander became a pupil-teacher at

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a school in Elgin. The following summer he studied Greekand Latin at the University of Edinburgh. When he wasseventeen he returned to Elgin, where he taught elocutionand music at Weston House Academy.

Grandfather Alexander Bell died in London in 1864 or1865, after which event Bell’s father moved to London,leaving his eldest son Melville James in charge of his pupilsin Edinburgh. While Alexander was still at Elgin, he wrote along letter to his father describing some experiments he hadconducted with tuning forks, electromagnets, and resona-tors, in complete ignorance of the experiments of Helm-holtz.

The elder Bell became well known in London, and hisspeech methods were in demand. He was made professor ofelocution at the University of London, and altogether hadachieved considerable success. In 1868 he was invited tolecture at Lowell Institute in Boston, which invitation heaccepted. Alexander, his son, now twenty-one years of age,was left in charge of the London classes, lectures, and les-sons.

THE BELL FAMILY MOVES TO CANADAIn 1870 the older brother, Melville James, died of tubercu-losis, a disease which earlier had taken the younger brother.Alexander was given a medical examination that disclosedthat he too was in some danger. The father, now thor-oughly alarmed, decided to abandon bis successful Londoncareer and to move to Canada. They settled near Brantford,Ontario, where Alexander soon recovered his health, andresumed his experiments with tuning forks and electromag-nets.

CLASSES IN BOSTON

In 1871 Alexander was asked to corne to Boston to workwith the pupils at the School for the Deaf, using his father’s

The Telephone 135

method of Visible Speech. After a time he returned toBrantford, but in 1872 he went once more to Boston wherehe opened a School for Vocal Physiology. Among his pupilswas Mabel Hubbard, the daughter of Gardiner Greene Hub-bard, a prominent Boston attorney. Mabel had become deafat the age of four and one-half years after an attack ofscarlet fever, and had been sent to Germany to learn lip-reading.

THE HARMONIC TELEGRAPHFrom his tuning-fork experiments Bell had conceived theidea of applying the principles he had developed to a devicehe called his harmonie telegraph. In general the principle ofthe harmonie telegraph lay in the use of various frequen-cies, which could be sent over a telegraph line simultane-ously and received on separate instruments, each of whichwas tuned to receive only a single frequency. During thewinter of 1872-1873 he carried on a series of experimentswith such an apparatus, but he became il1 and returned toBrantford in May to recover his health.

BOSTON UNIVERSITY AND GEORGE SANDERSHe did not return to Boston until October 1873 at whichtime he was appointed professor of vocal physiology in theSchool of Oratory of Boston University, but despite thenew activity he continued his private lessons. At that timealso, he became the tutor of a small boy named GeorgeSanders, who lived with his grandmother in a spacioushouse in Salem. The boy, whose father was ThomasSanders, had been born deaf. Thomas Sanders was a well-to-do leather merchant in Boston, and was to become Bell’smost important supporter, together with Gardiner Greene

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Hubbard. Bell was asked to live at the Sanders home inSalem, where he was given ample room for his experimentalequipment. He commuted to Boston by train each day anddevoted his evenings to teaching the Sanders boy, and afterthe boy had gone to bed he spent the remaining hoursworking on his harmonie telegraph. A fine friendship devel-oped between Bell, the Sanders, and the Sanders boy.

THOMAS A. WATSONBell was still a British subject at this time and believed thaton this account he would be unable to apply for a UnitedStates patent. He felt that his harmonie telegraph hadreached the stage of development at which it was patent-able, but his efforts to secure a British patent at this timewere unsuccessful.

His models of the harmonie telegraph were rather crude,and he felt that it was necessary to construct a more work-manlike device. TO this end he engaged the services of theCharles Williams shop at 109 Court Street, in Boston. It washere that he first met Thomas A. Watson, a Williams em-ployee, who was to become his assistant and lifetime friend.Watson served Bell in much the same way that Alfred Vailhad served Morse. The year was 1874. Bell was twenty-seven years of age and Watson was twenty.

THE PHONAUTOGRAPHAND THE REIS TELEPHONE

Although Bell’s primary interest at this time was in theharmonie telegraph, his mind was still occupied with im-proving his methods of teaching the deaf to speak. He per-formed experiments with a form of phonautograph, arecent development at the Massachusetts Institute of Tech-nology. This instrument traced the form of a sound wave

The Telephone 137

on a glass plate coated with lampblack. While conductingthese experiments at the Institute, he saw there for the firsttime a reproduction of the Reis telephone. Whether or nothe was influenced in his thinking by this mode1 is notknown.

From his experiments with the phonautograph, the har-monic telegraph, and even some experiments with humanears obtained from the Harvard Medical School, he gradu-ally evolved the idea of transmitting speech electrically. Heknew already that to transmit sounds accurately it wouldbe necessary to produce an undulating current which wouldfollow exactly the complicated waveform of the sound,and that a make-and-break current would not do. Theseideas were further developed during a visit to the familyhome in Brantford in the summer of 1874.

Upon his return to Boston, Bell described his ideas con-cerning the telephone to Sanders in some detail. Sandersshared Bell’s enthusiasm, but Hubbard was not at a11 ex-cited and wanted Bell to get on with his harmonie tele-graph, which he had helped to finance. Bell was now deter-mined to pursue his experiments with renewed vigor, and tothat end took over the top floor of the building in whichthe Williams shop was located.

Bell and Watson worked feverishly during the evenings andat such other times as they might be free from other duties.In 1875 Bell received a United States patent on his har-monic telegraph, a device on which Elisha Gray of Chicagohad also been working. Gray was the chief electrician of theWestern Electric Manufacturing Company, which at thattime produced telegraph equipment and related electricalapparatus for the Western Union Telegraph Company. Grayand Bell were both working on very similar ideas, but Grayhad a great advantage over Bell because of his connections

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with the Western Electric Manufacturing Company, thelargest producer of electrical apparatus in the United States.

MEETING WITH JOSEPH HENRY

While Bell was in Washington to obtain his patent on theharmonie telegraph, he met Joseph Henry, the secretary ofthe Smithsonian Institution who had been the mentor of SO

many experimenters in electricity, including Morse. Bellmentioned his ideas for the telephone to Henry, but ex-plained that his knowledge of electricity was too meager forthe problems involved, whereupon Henry advised him toget the knowledge he needed.

The Western Union Telegraph Company showed an inter-est in the harmonie telegraph and offered the use of itsfacilities in New York for further development, but Belldeclined the offer. Neither Bell’s nor Elisha Gray’s har-monic telegraph was developed commercially.

AGREEMENT WITH SANDERS AND HUBBARD

Early in 1875 Bell entered into an agreement with Sandersand Hubhard under which they were to contribute one-halfeach of the expenses Bell would incur in the developmentof his telegraph apparatus. No mention was made of anycompensation for Bell’s time and his living expenses. Bellbelieved that this agreement covered his work on the tele-phone as well as the harmonie telegraph, although it ap-peared later that the other two men who were parties to theagreement thought it covered only the telegraph.Bell’s income from teaching dwindled rapidly as he gave

more and more time to his experiments, with the result thathe was reduced to great poverty. He had hoped for the saleof his harmonie telegraph to the Western Union TelegraphCompany, but in this, as in other things, he was disap-

The Telephone 139

pointed. His spirits had fallen to a very low ebb, but withWatson’s encouragement they worked long hours to im-prove the harmonie telegraph and a new device, the auto-graph-telegraph, as Bell called it, or the telautograph, as itwas known later.

BELL% GREAT DISCOVERY

After much fruitless work in April and May 1875, thereoccurred on June 2, 1875, one of those fortunate accidentsthat SO often have resulted in great discoveries. Bell andWatson were at work on the harmonie telegraph in the atticof the Williams shop with Watson plucking the steel reedson the transmitter, and Bell tuning the corresponding reedson the receiver, when Bell became suddenly excited overwhat he had heard. He ran to Watson to find out whatWatson had done. The contacts on one of the reeds of thetransmitter had been welded together by the arc S O thatthey failed to open, and when Watson plucked the reed aninduced current was produced in the circuit, because theelectromagnet under the reed was energized, and an undu-lating current was produced by electromagnetic induction.This induced current caused the receiving reed to give off asound unlike that produced when the circuit was made orbroken through the contacts. Bell recognized at once thathe had discovered the means of producing the undulatingcurrent needed to transmit speech.

Bell made a sketch for Watson showing the details of anew apparatus he wanted Watson to build, and by the nextday his first telephone was ready. It consisted of two iden-tical instruments, each of which had a membrane of gold-beaters’ skin stretched over an opening in a box on the backof which rested a button attached to a hinged iron or steelarm. This arm formed part of a magnetic circuit with a

140 Char)ter l’en

small gap between it and one pole of an electromagnet. Theelectrical circuit for the two instruments was completedthrough a battery to energize the electromagnets.

After the Williams shop had closed for the day, the firsttests were carried out between the attic and the first floorof the shop over a pair of wires that Watson had strung. Bellhad been unable to hear Watson, but almost immediatelyWatson came running up the stairs exclaiming, “1 could hearyour voice; 1 could almost make out what you said.”Throughout the mont11 of June, Watson made one instru-ment after another according to the sketches which Bellprepared, as he sought to make an instrument that wouldtransmit the human voice clearly and distinctly.

Bell felt elated by his meager success, but Hubbard wasunimpressed and wanted Bell to Perfect his harmonie tele-graph and his autograph-telegraph, which in his opinion,were far more likely to produce tangible results and finan-cial returns. Sanders, on the other hand, believed in Bell’sability to make something of real value out of the presentflood of confused ideas and projects.

DESPAIR

The summer of 1875 was a wretched one for Bell becausein addition to his lack of funds he was in love with MabelHubbard, his former pupil. Hubbard was rather put outwith him, and his parents disapproved of his neglect of hisspeech classes. With these burdens pressing in upon him heagain fell ill, and once more sought to recuperate at hisparents’ home in Brantford. As his health returned, hischief concern was the condition of his finances, but he feltthat he could not or would not ask Hubbard or Sanders formore assistance. His thoughts turned to some of his father’swealthier neighbors. He caïled upon George Brown who

The Telephone 141

became interested in Bell% telephone, with the result thathe and his brother Gordon Brown agreed to lend Bell themoney he needed on the condition that they would beentitled to any foreign patents they might obtain, and thatBell was not to file for a United States patent until suchforeign patents, especially the British patent, had beenfiled, and that Bell would prepare the necessary patentspecifications as soon as possible.

Bell returned to Boston and the patent specifications weresoon ready, but the written agreement and the money fromthe Browns did not arrive. Things were getting SO desperatethat Bell was compelled to return to his teaching in order tolive, but he still stood by his agreement not to file for aUnited States patent until the British patent papers hadbeen filed. The year 1875 slipped away, and there was stillno word from the Browns. Hubbard and Sanders urged Bellto file his patent application regardless of his verbal agree-ment with the Browns. On November 25, 1875, Bell andMabel Hubbard became engaged, and as the prospectiveson-in-law of Hubbard his relations with that gentlemanimproved.

Bell arranged to meet the Browns at Toronto after Christ-mas, and on December 29 an agreement was concludedunder which each of the Browns was to pay Bell twenty-five dollars a month for six months for a half interest in anyforeign patents they might obtain.

Bell was working on improving the language of his specifi-cations. One very important modification later saved hispatent, namely a clause having to do with a variable resis-tance, presumably in a transmitter.

George Brown finally sailed for England on January 25,1876, and Bell as well as Hubbard were in New York to seehim off. They waited two weeks, during which time there

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was no word that the British patent application had beenfiled. Hubbard’s patience had run out, and, without theconsent of Bell, he filed for a United States patent on Feb-ruary 14, 1876. It was none too soon, for only a few heurslater Elisha Gray filed a caveat with the Patent Office on analmost identical invention.

NEW QUARTERSAt this time Bell moved his equipment from the top floorof the Williams shop building to his living quarters at 5Exeter Place where he and Watson now carried on theirexperiments. By this time Bell began to experiment withthe electrolytic transmitter, in which a wire attached to adiaphragm dipped into acidulated water contained in ametal cup. On the evening of March 10, 1876, they triedout this transmitter for the first time with excellent results.The transmitter was in one room and the receiver in an-other, when Bell suddenly shouted into the transmitter,“Watson, corne here 1 want you.” Bell had spilled acid onhis clothing and wanted Watson to help him. When Belldiscovered that Watson had heard his words distinctly onthe receiver the spilled acid was forgotten. They changedplaces back and forth, talking and listening, and both werefilled with enthusiasm.

TELEPHONE PATENT GRANTEDBell’s telephone patent was granted on March 7, 1876, andfortunately for Bell he had written his specifications inbroad enough language to caver not only his original elec-tromagnetic transmitter but also such other types as theelectrolytic.

THE TELEPHONEAT THE CENTENNIAL EXPOSITION

The year 1876 was the centennial of the nation’s founding,and in commemoration of that event a great World’s Fair

The Telephone 143

was held in Philadelphia. Bell had not entered his tele-phone, but Hubbard, who was in charge of the Massachu-setts educational exhibit, persuaded Bell to exhibit his tele-phone in that section. When the judges had reached theexhibit nearest that in which the telephone was shown, itwas late on a hot day, and the judges were about to leave.Dom Pedro, the Emperor of Brazil, who was with thejudges saw Bell, whom he had met previously in connectionwith his work on deaf mutes, and greeted him warmly. Thejudges followed Dom Pedro, who, when he learned of Bell’sexhibit, insisted that the judges inspect it. One after an-other of the judges, headed by Sir William Thomson, lis-tened while Bell recited from Hamlet into the transmitteron the opposite side of the hall. At first they were aston-ished and then became enthusiastic, as they alternately lis-tened and spoke into the apparatus.

They requested Bell to have the telephone moved to theJudges’ Hall for further tests. The day was Sunday, and onMonday Bell was to be in Boston for the annual examina-tion of his speech classes, SO that it was necessary for some-one else to look after the demonstrations. With some mis-givings on the part of Bell, William Hubbard was assigned tothe task. The Young Hubbard acquitted himself very well,SO that at least from the judges’ point of view the telephonewas the most important exhibit at the fair.

TESTING THE TELEPHONE

Late in July Bell went to Brantford once again, taking withhim two telephone sets. He made arrangements with theDominion Telegraph Company for the use of a telegraphline between Brantford and Paris, a distance of 8 miles, fora test of his apparatus. At first he used low-resistance re-ceivers, but the voices were obscured by line noises. When

144 Chapter l’en

he used high-resistance receivers, the voices came throughclearly. The battery that supplied the energy in this casewas in Toronto, 68 miles distant, SO that the circuit was inreality more than 70 miles in length.

On August 4 Bell’s father held a reception at his house inTutelo Heights, outside of Brantford, and arrangementswere made for the use of a telegraph line into Brantford,the last leg of which consisted of iron stove-pipe wiretacked on wooden fente posts to bring the circuit into theBell home. This test was also eminently successful and de-lighted the assembled guests. Apparently a11 of these testswere made with the original electromagnetic telephone inwhich the transmitter and receiver were one and the same.

During that summer Bell offered Watson a one-tenth inter-est in the telephone if Watson would devote a11 of his timeto further work on its improvement. Watson was reluctantto accept the offer because he, like Bell, was in need ofmoney, and his job at the Williams shop provided a steadyincome. After several weeks, however, he did accept andmoved into Bell’s quarters on Exeter Place. Here the workcontinued and soon resulted in an important improvement,the substitution of a thin iron disk for the membrane usedin previous instruments. A second great improvement, madeby Watson, was the use of permanent magnets in the re-ceivers in place of the soft iron cores of the electromagnets.With this instrument batteries were unnecessary.

WESTERN UNIONREFUSES TO BUY THE TELEPHONE

Despite his successes Bell felt frustrated, because he wantedto get married and he wanted to repay those who had SO

generously supported him. With these thoughts in mind he

The Telephone 145

offered his telephone to the Western Union Telegraph Com-pany for $100,000 but was refused.

SO far Bell’s telephone had brought him no financial re-turns except for such fees as he collected for his lecturesand demonstrations before various organizations, of whichthere were many. The first actual telephone installation wasmade between the Williams shop in Boston and the Williamshome in Somerville, a distance of three miles.

BELL IS MARRIED

Alexander Graham Bell and Mabel Hubbard were marriedon July 11, 1877, and early in August they embarked on asteamship bound for England, where they remained for fif-teen months. In England, Bell gave demonstrations beforescientific and other gatherings, and finally before QueenVictoria. While he was still in England the Electric Tele-phone Company was organized, and began installing tele-phones in London, using the Bell inventions. As was thecase with Morse, Bell was unable to obtain a British patentbecause of prior publication. Riva1 telephone companiessprang up, including one promoted by Fred Gower, whomBell had employed earlier in connection with his Americandemonstrations.

ORGANIZATION OF TELEPHONE COMPANIES

In the United States Bell’s partners had formed a companycalled the Bell Telephone Association in which Hubbard,Sanders, and Bell each owned a three-tenths interest, andWatson one-tenth. The company appointed agents in vari-ous parts of the country whose duty it was to make tele-phone leases and make telephone installations. At firstthese were only private lines, sometimes on the same prem-ises and sometimes between office and home.

146 Chapter Ten

Thomas Sanders had invested large sums of money inBell’s telephone up to the point that his credit was be-coming stretched, and he was in danger of losing his leatherbusiness. In the spring of 1878 Sanders’s relatives came for-ward with the funds needed to organize the New EnglandTelephone Company, which was licensed by the Bell Tele-phone Association to engage in the telephone business,using Bell equipment.

The Bell telephone at this time was still the simple electro-magnetic device in which the same instrument served asboth transmitter and receiver. In order to cal1 the person atthe other end of the line it was necessary to tap the dia-phragm of the instrument SO as to produce a faint noise atthe other end. Watson made a mechanical device to accom-plish the same purpose, which was called Watson’s thumper.Shortly thereafter, however, he invented the polarized bell,actuated by a small magneto.

The first crude exchange was installed by the HolmesBurglar Alarm Company in Boston in May 1877. Tele-phones in various financial institutions that had burglaralarms could be connected through the Holmes centraloffice. The first commercial exchange was put into servicein New Haven, Connecticut, on January 25,1878.

INFRINGEMENT BY THE WESTERN UNION

TELEGRAPH COMPANY

In December 1877 the Western Union Telegraph Company,which earlier had refused to buy Bell’s patent, organizedthe American Speaking Telephone Company. It owned thepatents on the Edison carbon transmitter, Gray’s inven-tions, and the Page induction coi1 patent. For the WesternUnion Telegraph Company to engage in the telephone busi-ness was a relatively simple matter because it already owned

The Telephone 147

the necessary lines, the manufacturing facilities, and hadample capital.

With the Edison transmitter and the induction coi1 West-ern Union had a telephone far superior to that of Bell andsoon made great inroads into the telephone business. TheBell company by this time had about three thousand tele-phones in service.

Hubbard and Sanders brought suit against the WesternUnion Telegraph Company for patent infringement. WithBell still in England it was necessary to communicate bytable many times to clarify disputed points. Bell becameconvinced that it was useless to fight the powerful WesternUnion Telegraph Company and was completely discour-aged.

He left England late in October 1878 with his wife and asmall daughter, born to them in May 1878, with the inten-tion of going to Brantford for an indefinite stay. Bell was,however, badly needed to testify at the tria1 in the infringe-ment suit against Western Union. Watson, who had goneto Quebec to meet the ship which docked on November 10,1878, succeeded in persuading the reluctant Bell to returnto Boston, where he entered Massachusetts General Hospi-ta1 for an operation. While he was there he made severalimportant depositions of great importance to the infringe-ment proceedings.

BELL PATENT UPHELD

The tria1 lasted about one year, at the end of which time asettlement was agreed upon under which the patent rightsrelating to the telephone were to be pooled; the WesternUnion was to receive a one-fifth interest in the Bell com-pany rentals and four-fifths were to be retained by the Bellcompany. This settlement was a clear victory for the Bell

148 Chapter Ten

company in that it established beyond doubt the validity ofits patents. One of the factors influencing the outcome wasthe acquisition by the Bell company of the Blake transmit-ter in October 1878, making the competitive positions ofthe two companies more nearly equal.

TRANSMITTERSAlthough Bell had experimented with the liquid transmitterin 1876 and found that it yielded much better results thanhis electromagnetic transmitter and receiver, he clung to hisoriginal invention tenaciously until the Bell company wascompelled by competition to adopt the Blake transmitter.There were many forms of transmitter in the early historyof the telephone, including Reis’s metallic contacts, theliquid transmitter, the Emile Berliner transmitter of 1877,the Edison carbon transmitter, the Blake carbon and plati-num transmitter, the Hunnings granular carbon and plati-num transmitter and its later improvements, and the solidback transmitter invented in 1890 by A. C. White, usingcarbon disks and granules. The Dolbear electrostatic trans-mitter was never used in actual practice.

THEODORE N. VAILWhile this book is a history of electricity and magnetism, itis also inevitably bound up with persons and corporations.Up to the time of Bell’s sojourn in England the movingspirits behind the Bell companies were Bell, Hubbard, Sand-ers, and Watson. In May 1878, Theodore N. Vail, who hadbeen general superintendent of railway mails for the UnitedStates Post Office, was given the position of general superin-tendent of the Bell company. It was his hard-nosed attitudewhich was to a large extent responsible for the favorablesettlement with Western Union.

The Telephone 149

Figure 10.2 Alexander Graham Bell (From Smithsonian Insti-tution)

150 Chapter Ten

EVOLUTION OF THE BELL COMPANIES

The Bell Telephone Association and the New England Tele-phone Company have already been mentioned. On July 30,1878, the Bell Telephone Company was incorporated inMassachusetts, with a capital of $450,000, to succeed theoriginal Bell Telephone Association. On March 13, 1879,the National Bell Telephone Company was incorporatedwith a capital of $850,000, and it controlled the New En-gland Telephone Company and the Bell Telephone Com-pany. Early in 1880 the American Bell Telephone Companywas incorporated in Massachusetts with a capital of$10,000,000, and its stock was exchanged for that of theNational Bell Telephone Company, on the basis of sixshares for one, after which transaction the latter companywas dissolved. Finally the American Telephone and Tele-graph Company was incorporated in New York on March 3,1885, to take over the long lines of the Bell companies, andit eventually became the owner of the majority stock inter-est in the various regional telephone systems. Its first presi-dent was Theodore N. Vail.Colonel William H. Forbes, together with his brother

J. Malcom Forbes, H. L. Higginson, and Lee, Higginson andCompany had by May 1, 1880, acquired a controlling inter-est in the American Bell Telephone Company. ColonelForbes, who was a close friend of Sanders, had purchased alarge block of stock through Sanders in 1879, and in thatyear became president of the National Bell Telephone Com-pany. When the American Bell Telephone Company wasorganized, Forbes became its president, with W. R. Driveras treasurer and Theodore N. Vail as general manager.

THE DIAL TELEPHONE

The many improvements made in telephone apparatus inlater years are beyond the scope of this book, except that

The Telephone 151

mention should be made of the invention of the automaticor dia1 telephone, by A. B. Strowger in 1889, which wasfirst used in the La Porte, Indiana, telephone exchange in1892.

BELL LABORATORIES AND WESTERN

ELECTRIC COMPANY

Many inventions and discoveries with uses in and outsidethe telephone industry, such as the transistor and the solarcell, have been made by the Bell Telephone Laboratories.The Western Electric Company, successor to the WesternElectric Manufacturing Company of Chicago and the Wil-liams shop of Boston, a wholly owned subsidiary of theAmerican Telephone and Telegraph Company, has pro-duced telephones, switchboards, tables, and the many otherkinds of equipment required in the telephone business.

OTHER TELEPHONE SYSTEMS

The telephone has become almost universal. In most coun-tries outside the United States telephone systems have beenlargely government-owned and have been connected withthe post office. In some countries telephone systems havebeen installed by foreign private corporations such as theInternational Telephone and Telegraph Company.

There are numerous telephone manufacturing companiesin other countries, especially in Sweden, England, France,Holland, and Germany. In the United States there are sev-eral manufacturers other than the Western Electric Com-pany, producing telephone equipment used by independenttelephone companies. Although the Bell system controlsthe greater part of the telephone business in the UnitedStates, it is by no means a complete monopoly.

11

Electric Lighting

Three forms of electric lighting have been known for a longtime. The electric spark, which later became the electricarc, was the first to be observed. Next came the glow inpartially exhausted glass globes excited by an electrical dis-charge, and finally came the glow of a wire heated by thepassage of an electric current.

Hawksbee performed a series of beautiful experiments inpartially exhausted glass globes in 1705. Some of thesewere globes that he used as part of his frictional electricmachines. Jean Picard had noted similar effects in the evac-uated portion of a Torricellian tube in 1675 but did notknow that they were due to electricity. Sir Humphry Davyfirst exhibited the electric arc at a lecture at the RoyalInstitution in London in 1809. Current for the experimentwas supplied by a large battery that had recently been in-stalled. The dazzling light of the carbon arc made a deepimpression upon the gathering.

After the invention of the Leyden jar it was discoveredthat a discharge from a battery of such jars would heat oreven fuse small wires. Soon after Volta’s invention of hispile, the heating effects of electric currents were observed.Many of the batteries were sufficiently powerful to fuseiron rods. It is not known who first proposed using suchheated conductors as sources of light.

ARC LAMPSAs long as the voltaic battery remained the only source ofcurrent electricity it was impracticable to use electricity forillumination because of the expense involved. With thedevelopment of magnetoelectric machines and later ofdynamoelectric machines, interest in electric lighting sprang

Electric Lighting 153

up almost immediately. The first practical arc lighting in-stallation, as was previously mentioned, was made at SouthForeland Lighthouse in England in 1858, using a Nolletmagnetogenerator. Beginning in the middle 1870s arclamps and arc lamp machines were produced in great num-bers and varied forms.

ARC LAMP MECHANISMSThere were literally hundreds of different arc lamp feedmechanisms. The arc lamp required that the electrodes bein contact for starting and then be separated by a sufficientspace to maintain a steady arc of maximum brightness. Usu-ally arc lamps were operated .in series S O that the samecurrent passed through a11 of the lamps in the circuit. Inorder to prevent the entire circuit from being interruptedby the outage of a single lamp, a short-circuiting device wasan essential part of the lamp.

Some of the control mechanisms were simple, while otherswere complicated and ingenious. In general the feed mecha-nisms employed electromagnets, racks and pinions, ratch-ets, and gears. Sometimes the Upper carbon dropped bygravity as it burned, and in some cases both carbons weremoved together mechanically as they became shorter. Inmost instances the power was supplied by electromagnets,but there were some that contained a clockwork that re-quired winding.

Between the years 1841 and 1844 Deleuil and Archereaudevised an arc lamp regulating mechanism that they appliedto two lamps installed in Paris. Because these lamps weresupplied by Bunsen batteries, the expense of operationproved to be prohibitive. In 1846, however, an arc light wasused in a presentation of the opera The Prophet in Paris,using a lamp mechanism made by Duboscq. Several inven-

154 Chapter Eleven

tors in England were also engaged in the design of arc lights,notably Wright and Staite. Staite’s lamps were used forlighting a large hall, but the great cost of batteries made a11of these attempts impracticable.

CARBONS

The carbons used in the early period of arc lighting weretut from pieces of coke. More satisfactory carbons weremade later from a carbon paste molded under pressure.The paste consisted o f fmely divided coke mixed with acarbonaceous binder. After forming under pressure, therods were heated to drive off the unwanted gaseous ma-terials and to form a hard carbon rod. A later improvementwas made by copper-plating most of the length of the car-bon rod to increase its conductivity.

MANUFACTURERS

In Europe the machines of Nollet, Siemens, Wilde, Ladd,Gramme, Schuckert, Ferranti, Hefner and Alteneck,Gulcher, Jablochkov, and others were used for arc lighting.In the United States the principal machines were those ofBrush, Thomson-Houston, Weston, and Wallace-Farmer.Each of the American firms mentioned manufactured acomplete arc lighting system including lamps, generators,regulating devices, switchboards, and other accessories.

STREET LIGHTING

For twenty years the only arc lamp installations in regularservice were the British lighthouses previously mentioned.In 1876 Jablochkov, a Russian, invented a very simple formof arc lamp known as the Jablochkov candle. In this lamptwo carbon rods were placed parallel to each other andabout 7s inch apart. The intervening space was filled with a

Electric Lighting 155

Figure 11.1 The Jablochkov Candle. This improved carbon arc con-sisted of two carbon rods separated by plaster of Paris. Its greatadvantage was that no mechanical moving parts were needed to keepa constant arc length. It was used in the first electric street lightingon the Avenue de 1’0pera in Paris in 1878. (Courtesy Burndy Li-

156 Chapter Eleven

kaolin cernent that acted both as an insulator and a binder.At the top of the candle was placed a powdered carbonmixture or a loose bit of carbon bridging the gap betweenthe rods, SO that when the current was turned on an arc wasestablished at each lamp. The Jablochkov system used analternating-current generator SO that the two carbon rodswere consumed at the same rate. This was the first commer-cial use of alternating currents.

The Jablochkov candle gave a soft pleasing light and be-cause of its simplicity gained favor for street lighting pur-poses. An installation of Jablochkov candles, which oper-ated successfully for three years, was made on the Avenuede l’Opéra in Paris about 1877. Alternating current forthese lamps was supplied by Gramme machines. Each lampcontained four candles that were switched on in turn auto-matically as the preceding candle was consumed. Eachcandle burned about 1% hours.

In the United States Charles F. Brush installed arc lampsin the show Windows of the Wanamaker store in Philadel-phia in 1878. Twenty lamps were employed for this pur-pose, supplied by five Brush dynamos. Crowds of peoplegathered to see the new lights, and to them it was a demon-stration of a new wizardry of which they had little concep-tion.

Charles F. Brush was a resident of Cleveland, and hislamps, dynamos, and other equipment were manufacturedby the Cleveland Telegraph Supply Company. The Wana-maker installation excited the admiration of two youthfulprofessors at the Philadelphia Central High School: ElihuThomson and Edwin J. Houston. Inspired by the success ofthe Brush installation, they set about building an arc lightmachine, with the financial assistance of George S. Garrett.

Electric Lighting 157

The Thomson-Houston machine and lamps were successful,and installations of these followed soon thereafter.

An experimental street lighting installation, consisting oftwelve Brush arc lamps, was turned on in Cleveland onApril 29, 1879. During the same year a company was orga-nized in San Francisco known as the California ElectricLight Company, which proposed to go into the business offurnishing arc light service for the streets and buildings ofthe City. The company’s first installation consisted of twoBrush dynamos, one with a capacity of six lights and theother sixteen lights. Business grew rapidly SO that additionsto the plant were needed almost immediately. The firstlamps were hung in business places, but within a short timecontracts were made for the lighting of streets.

As news of the success of arc lighting spread, there was animmediate demand for electric lights from a11 parts of thecountry, SO that for several years Brush, Thomson-Houston,Weston, and Wallace-Farmer were unable to keep up withthe demand for equipment. By 1884 or 1885 arc lightingfor streets was in general use throughout the United Statesand also in Europe. One interesting application, developedby the Brush company, was the use of ta11 steel towers, onwhich were mounted from four to eight arc lights to serveas a sort of artificial moon. Although a great many of theseinstallations were made, they were abandoned within ashort time.

Arc lights were well suited to street lighting and for manyyears were also used successfully for the lighting of largebuildings. They were not, however, well adapted to thelighting of homes and smaller buildings, because the lightwas too intense, it was not of the proper quality, and itflickered considerably. Usually arc lamps were operated on

Figure 11.2 A 1n woved Brush Arc Generator. This dynamo was in use &out 1880,Kourksy General Electic Compaq,)

Electric Lighting 159

Figure 11.3 Dedication of Lighting Tower. This tower, located inBridge Square, Minneapolis in 1883, was 257 feet high and carriedeight 4000 candle power lamps. As shown in the picture the lampswere lowered for trimming. (Courtesy Minnesota Historical Soci-ety)

1 6 0 Chapter Eleven

series circuits that required the use of dangerously highvoltage.

ENCLOSED ARC LAMPSThere was little change in arc lighting for some years until1893, when the enclosed arc was introduced by Louis B.Marks. The enclosed arc was used extensively for the inte-rior lighting of stores and larger halls, but it was less ef-ficient than the open arc light. One of its more importantadvantages was that the carbons lasted ten to twelve timesas long as in the open arc.

FLAMING ARCSIn 1898 Bremer of Germany invented the open flaming arc,in which the carbons were impregnated with various metal-lit salts. It produced intense illumination with colors de-pending upon the salts used. This lamp had an efficiency ofabout 35 lumens per watt as compared with 5 to 8 lumensper watt in the enclosed arc and about 15 lumens per wattin the ordinary open carbon arc. A lumen is the quantity oflight which falls on a square foot of area of a sphere of1 foot radius at the tenter of which is a 1 candlepower lightsource. Since the area of such a sphere is 12.57 square feet,the theoretical lumens would be 12.57 per candlepower. Inpractice, because some of the light of any actual lightsource is blocked off by the lamp itself, the total lumensare sometimes taken to be 10 times the horizontal candle-power.

INCANDESCENT ELECTRIC LIGHTSMethods of lighting by electricity other than the arc lamphad been tried by various experimenters beginning in theearly part of the nineteenth Century. The glow emitted by awire heated by an electric current had been observed soon

Electric Lighting 161

after the invention of the voltaic battery, and in fact ironand platinum wires had been heated to incandescence oreven volatilized by the discharge of Leyden jars.

Sir William Grove, the inventor of the battery bearing hisname, devised a lamp in 1840 in which a platinum wire washeated to incandescence by an electric current, while en-closed in a glass tumbler inverted over water.

Apparently the first incandescent lamp for which a patentwas granted was that of Frederick de Moleyns of Chelten-ham, England. He received a British patent on August 21,1841, for a lamp in which finely divided carbon was fedinto a gap between two coils of platinum wire connected toopposite poles of a battery. The platinum wires and a glasstube containing a supply of powdered charcoal were en-closed in an exhausted glass globe.J. W. Starr of Cincinnati, Ohio, sought a British patent in

1845 covering two incandescent lamps. In one lamp thelight source was a platinum strip enclosed in a glass globe.The length of the platinum strip was variable SO as to adaptthe lamp for different battery voltages. In the second lampthe substance to be heated to incandescence was a shortpiece of carbon rod which was held by clamps at each end.This assembly was placed in an expanded chamber at theUpper end of a Torricellian tube and therefore operated in avacuum. Such a lamp could be used for only a short timebefore the glass became blackened, and like its predecessorsit proved impracticable.

Other incandescent lamps were devised by Staite, Nollet,Roberts, Way, Shepard, de Changy, Gardiner, Morris,Farmer, Swan, Lodyguine, Konn, Sawyer and Man, andmany others. Moses G. Farmer lighted the living room ofhis home in Salem, Massachusetts, during the month of July1859 by means of incandescent electric lights, the current

162 Chapter Eleven

for which was supplied by Bunsen batteries. These lamps,which burned in open air, were merely strips of platinum,tapered at both ends and clamped to terminal pieces.

Sir Joseph Swan’s lamp of 1860 had a horseshoe-shapedfilament made of a strip of carbonized paper, operating in avacuum. With the air pumps available at that time the vac-uum was rather imperfect, and this fact led to the failure ofthese lamps. In 1865 the Sprengel mercury pump was in-vented which made possible high vacuums. In 1878 Swanmade lamps with carbon filaments which gave good results.There is considerable justification for the claim that Swanrather than Edison was the inventor of the incandescentlamp, except that Edison produced the first commerciallyacceptable incandescent lamps and accessories.

EDISON’S INCANDESCENT LAMP

In the United States the same problem was attacked withgreat energy by Farmer, Sawyer and Man, Maxim, and Edi-son. Farmer, Sawyer, and Maxim each produced graphitelamps in 1878 a11 of which operated successfully, but as wasthe case with a11 other lamps SO far produced they had shortlives. The globes soon became black, and they were expen-sive.

Edison began work on the incandescent lamp in his labora-tory in Menlo Park, New Jersey, in 1877. In his first lampsEdison experimented with carbon, then with platinum,with metallic alloys, and then returned to carbon. Severalpatents were granted to him on the metal filament lamps.

In 1877 and 1878 Edison was for the most part occupiedwith his work on the phonograph. In July 1878 he accom-panied an expedition to Wyoming to view an eclipse of thesun. On his return late in August, he went first to Ansonia,Connecticut, to visit the Wallace Brass works. Wallace and

FigureGeneral

Electric Lighting 163

11.4 Edison’s First Commercially Used Lamp’ Electric Company)

(Courtesy

164 Chapter Eleven

Farmer were manufacturing arc lights and arc light dyna-mos. When Edison returned to Menlo Park, he brought withhim one of the small dynamos.At Menlo Park Edison now attacked the problem of the

incandescent light in earnest. For more than a year he ex-perimented with a11 sorts of materials, including metals, car-bonized thread, paper, wood fiber, bamboo, palm leaves,and whatever else seemed to hold any promise of fulfillingthe conditions required for a durable filament. Finally onOctober 21, 1879, he made a lamp with a carbonizedthread filament that burned for forty-five hours before itfailed. He applied for a patent on November 4, 1879, whichwas granted on January 27, 1880.

EDISON ELECTRIC LIGHT COMPANY

Edison was not only a great inventor but also an excellentbusinessman and an organizer. On October 17, 1878, morethan a year before he made his first successful incandescentlamp, The Edison Electric Light Company was organizedwith a capital of $300,000. The stockholders and directorsincluded some of the most important New York bankersand financiers.

After his successful carbonized thread lamp, Edison con-tinued his experiments and made rather a large number oflamps with carbonized paper filaments. Incidentally, thename filament was first applied by Edison. Before that timethe glowing elements in the lamps had usually been desig-nated as burners, to correspond with gas burners.

On Sunday, December 21, 1879, the New York Heraldprinted a full-page description of Edison’s lighting system,which by this time included not only his incandescent lampbut also his dynamo and auxiliary equipment. After thepublication of the article in the Herald, gas company stocks

Electric Lighting 165

fell rapidly in price and Edison Electric Light Companyshares were traded for as much as $5000.

MENLO PARK

On New Year’s Eve 1879, an experimental installation oflamps with carbonized paper filaments was made at MenloPark. Special trains were run from New York City to ac-commodate the crowds of people who came to see the newlights. Edison had succeeded in “subdividing” the electriclight according to the queer expression that had becomecurrent during the preceding period. For some unaccount-able reason people had the notion that the electric light wasthe arc light, and it was argued with great vehemence thatthe light could not be subdivided, that is, produced insmaller units of lower intensity than the familiar arc lamp.

THE SEARCH FOR BETTER

FILAMENT MATERIALS

Despite his successes Edison was not satisfied that he hadobtained the best possible material for his lamp filaments,and continued his experiments with various vegetablefibers. He dispatched emissaries to Japan, China, Burma,Ceylon, and South America to obtain specimens of bam-boo, grasses, palms, and wood. His greatest success was withbamboo, and for nine years his lamps were made with car-bonized bamboo filaments.

IMPROVEMENTS IN LAMP SEALS

AND IN DYNAMOS

He was also working on various other problems connectedwith the incandescent lamp such as improving the sealaround the lead-in wires, obtaining a better vacuum by ex-pelling the occluded gases in the filament, and making a

166 Chapter Eleven

Figure 11.5 An Edison Bipolar Dynamo. This generator was deoped in 1886. (Courtesy General Electric Company)

vel-

more uniform filament. In some of these endeavors he wasaided by the discoveries made by others.

Edison was engaged also in developing a constant-voltagedynamo, with low interna1 resistance and greatly improvedefficiency. Many of the earlier machines had efficiencies ofonly 50 to 60 percent, but Edison succeeded in building amachine with more than 90 percent efficiency.

Electric Lighting 167

FIRST COMMERCIAL INSTALLATIONS

The first commercial installation of Edison’s new lamps anddynamos was made on the steamship Columbia which wasunder construction in the shipyards at Chester, Pennsylva-nia, for the Oregon Railway and Navigation Company. Thisinstallation included four dynamos, three of which oper-ated in parallel, with the fourth used as an exciter. Thisplant went into operation on May 2, 1880. Early in January1881 an Edison lighting system was installed in the litho-graphing plant of Hinds, Ketchum and Company a t229 Pearl Street, New York. About 150 installations in pri-vate plants were made during the following two years withmore than 30,000 lamps.

Edison’s lamps by this time were equipped with the nowfamiliar screw base. As the production of lamps increased inquantity, the quality improved and the cost was greatlyreduced. The growth of the lamp business soon made thefacilities of the Menlo Park laboratories inadequate. A fac-tory building was purchased in Menlo Park in 1880 for useas a lamp factory, but this also soon became too small, SO

that in 1881 a group of factory buildings in Harrison, NewJersey, was taken over by Edison for the manufacture oflamps. This plant was operated by the Edison Lamp Com-pany, a separate company that had been organized in 1880.

PEARL STREET, THE FIRST CENTRAL STATION

FOR INCANDESCENT LIGHTING

Edison had realized for some time that substantial econo-mies were possible through pooling the generating facilitiesfor a large number of customers in a single plant, or inother words through the construction of a central station.Savings would result from what is now known as diversityamong the customers and also from greater efficiency re-

that same mont11 the Edison Electric Illuminating Companyof New York was incorporated. This company made a con-tract with the Edison Electric Light Company for a com-plete installation of a generating station, underground ca-bles, wiring of buildings, lamps, fixtures, meters, and a11other auxiliary equipment, for incandescent light service inan area o f about one-sixth of a square mi le , boundedroughly by Wall Street, Nassau Street, the East River, andSpruce Street.

The plant was constructed at 257 Pearl Street, with boilersat the street level and engines and dynamos on the floorabove. Engines and boilers were purchased from the manu-facturers of such equipment. Dynamos were built by theEdison Machine Works on Goerck Street in New York City.Sockets, switches, and other equipment were produced byBergmann and Company on Wooster Street. Bergmann hadbeen associated with Edison at Menlo Park. Undergroundconduits and fittings were made by the Underground TubeCompany at 65 Washington Street.

The Pearl Street plant and distribution system were com-pleted and put into operation on September 4, 1882. Thesystem was an unqualified success notwithstanding manymisgivings of Edison and his associates. This was the firstincandescent central station in the United States, but therehad been many earlier stations supplying arc lamp service.

The success of the Pearl Street station resulted immedi-ately in orders for similar systems from a11 parts of thecountry. The load on Pearl Street grew rapidly, SO that the

Electric Light ing 169

Figure 11.7 Thomas A. Edison (Courtesy General Electric Com-PanY)

Electric Lighting 171

requests for service soon exceeded the capacity of the sta-tion. In the original installation there were six Jumbo dyna-mos capable of supplying 7200, 16-candlepower lamps.

SCHENECTADY WORKS

In order to fil1 the flood of orders for a11 types of equip-ment the various Edison factories expanded enormously. In1886 the Edison Machine Works moved to Schenectady,New York, where it later became the nucleus of the greatGeneral Electric Company works. Harrison, New Jersey, re-mained the site of one of the greatest lamp factories.

FOREIGN INCANDESCENT LIGHT INSTALLATIONSThe Paris exposition of 1881 gave great impetus to theadoption of incandescent lighting. At this exposition Edi-son exhibited a complete lighting system, including gener-ators, conductors, switches, fuses, lamps, sockets, and fix-tures. Other exhibitors were Swan and Lane-Fox ofEngland, and Maxim of the United States. In 1882 therewas an electrical exposition in the Crystal Palace in Londonthat included many electric lighting exhibits and a completeinstallation by Edison of his generating equipment, lamps,sockets, and accessories.

At about the same time the Edison Electric Lighting Com-pany of London Ltd. was constructing a plant in a buildingat Holborn Viaduct to serve nearby customers, amongwhom was the British Post Office. This plant began opera-tion in March 1882, about six months earlier than the PearlStreet station.

Early Edison lamps had no base, but the lead-in wires weremerely bent back over the neck of the lamp and madecontact with two spring clips in the socket. In the latterpart of the year 1880 the first Edison screw base lampsappeared, followed by improvements in 1881.

manufacturers used a different lamp base and socket. Grad-ually, however, there was a shift to the Edison screw base,and in many cases, in which a different socket had been in-stalled originally, adapters were provided SO that Edisonlamps could be used. In the early 1900s the Edison basebecame the standard for the United States except for spe-cial applications. Many European manufacturers alsoadopted the Edison base , but some, even to the presentday, use a bayonet type of base, similar to that used onautomobile lamps.

IMPROVED LAMPSThe bamboo filament lamp was produced in great numbersand was found to be rugged, but its efficiency was onlyabout 1.7 lumens per watt when new, and only half thatamount when the bulb had become blackened. With con-stant research and consequent improvements the efficiencyreached 2.5 lumens per watt in 1881. There was also a grad-ual improvement in manufacturing methods, in lamp con-struction, in lamp life, and a substantial decrease in cost. In1890 or thereabouts, there was a significant change whenthe squirted filament was introduced. This filament, as thename implies, was made by squirting a carbonaceous pastethrough a die, after which the soft thread was carbonized.Lamps of this type and the improved Gem lamp of 1905were manufactured until about 1918, but long before thattime metal filament lamps had taken over the great bulk ofthe market.

Electric Lighting 173

OTHER TYPES OF LAMPSMany new types of lamps came into existence begimiing atthe turn of the Century. Aside from the arc lamp improve-ments previously mentioned, came the low-pressure mer-cury arc lamp invented by Peter Cooper Hewitt in 1901,and with it the mercury arc rectifier. Also in 1901, H. W.Nernst of Germany invented the Nernst lamp in which thelight source was composed of one or more rods of moldedoxides of zirconium and yttrium. This material was prac-tically a nonconductor when cold but had an increasedconductivity with increase in temperature. It was necessarytherefore to provide a heating coi1 to raise the temperaturesufficiently SO that current would flow through the gloweritself. This lamp was used for only a few years for indoorand outdoor lighting.

The osmium lamp was developed in 1905 by Dr. Auervon Welsbach, followed by the tantalum lamp in 1906 byDr. Werner von Bolton, both of Germany. The sinteredtungsten lamp was patented in Germany by Just and Hana-man of Vienna in 1903, and a United States patent wasapplied for in 1905, but because of other claims the patentwas not granted until 1912.

While tungsten was an excellent material for lampfilaments, the metal was S O brittle that it had not beenpossible to draw it into wire. The filament produced by theJust and Hanaman method was formed by taking finelydivided tungsten, mixing it with a binder, squirting thepaste through a die, and sintering the particles of tung-sten together by passing a current of electricity throughthe thread that had been formed. Lamps made by thismethod were far more efficient than carbon lamps, but thefilament was weak and easily broken, and the lamps wereexpensive. Nevertheless the sintered tungsten lamps went

In a relatively short time drawn-wire tungsten filamentlamps were produced for the market. In 1913 Dr. IrvingLangmuir, also of the General Electric Company, perfectedthe gas-filled tungsten lamp. This lamp was a great stepforward because the filaments in these lamps could be oper-ated at considerably higher temperatures and consequentlyhigher efficiencies, particularly in the larger sizes, whereefficiencies of 20 lumens per watt were reached.

TUBE LIGHTINGGeissler tubes, which were mentioned previously, were pro-duced in great numbers around the middle of the nine-teenth Century. Some of these tubes contained mercury orvarious of the rare gases in small amounts, which gave offtheir characteristic color spectra when excited by the dis-charge of an electrostatic machine or an induction coil.Many of the tubes were also made with glass containingsalts that fluoresced in beautiful colors when they wereexcited.

About the year 1895, D. McFarlan Moore of the UnitedStates began experimenting with long glass tubes filled withcarbon dioxide gas, which gave off a good quality whitelight when a crurent of electricity was sent through them atrelatively high voltage. Beginning at about the year 1904,many installations of such tube lighting were made, espe-cially in stores.

Geissler had used neon and other rare gases in bis tubes,but such gases were expensive to produce. Georges Claudeof France discovered a method of obtaining neon cheaply,

Electric Lighting 175

and about 1910 began making neon tube lighting, but itwas not until 1922 that such lighting was introduced com-mercially, largely for advertising.

The principle underlying sodium vapor lamps was dis-covered about 1910, but they were first used for highwaylighting in 1933.

High-pressure mercury lamps were developed in 1912, butthese lamps, now widely used for highway and airport light-ing, were not introduced commercially until 1934.

FLUORESCENT LAMPS

The early research work on fluorescent lamps was done inGermany and in England. It had long been known thatcertain minerals would fluoresce under the influence ofultraviolet light, but no practical application was made ofsuch phenomena until many years later. The first fluores-cent lamps were made in Europe in 1934. They were intro-duced commercially in the United States in 1938. The fluo-rescent lamp is essentially a low-pressure mercury arc lamp,producing ultraviolet light, which in turn causes a coatingon the inside of the tube to fluoresce with a color depend-ing upon the kind of material used.

LAMP EFFICIENCIESEfficiencies had increased enormously with the introduc-tion of new types of lamps. Sodium vapor lamps had effi-ciencies of about 70 lumens per watt. High-pressure mer-cury lamps yielded from 40 to 55 lumens per watt, andfluorescent lamps produced a lifetime average of 51 lumensper watt. These figures may be compared with the earlyEdison lamps that yielded less than 2 lumens per watt.

bulbs, automobile lamps, sterilamps, sunlamps, photo-graphie lamps, glow lamps, and a host of others.

12

Alternating Currents

The early electric lighting systems, bath arc light and incan-descent, used direct current with the notable exception ofJablochkov candles, which used alternating current SO thatthe electrodes might burn at the same rate. Some of thefirst magnetogenerators, such as the Nollet machines, hadbeen built as alternators.

Electrical designers and manufacturers of the early 1880swere not altogether ignorant of alternating currents, butfrom the viewpoint of that day direct current offered SO

many advantages that alternating current had not been con-sidered seriously . Among other things there was no alternat-ing-current motor, and alternating-current generators couldnot be connected in parallel as Edison was doing with hisdynamos. Direct current was suited to electroplating, elec-trolytic processes, and could be used for charging storagebatteries. Arc lights performed better and more quietly ondirect current, and many electromagnetic devices would notfunction satisfactorily on alternating current.

Despite a11 of these disadvantages there was neverthelessone great advantage that was recognized after a time,namely that alternating currents could be readily and effi-ciently changed from one voltage to another, and sincehigher voltages were essential for transmission over dis-tances greater than about % mile, it was inevitable that al-ternating currents would be employed.

THE TRANSFORMERThe heart of the alternating-current system was the trans-former, and when the transformer had been brought to asatisfactory stage of development the alternating-currentsystem was established. The transformer was not really new

produce strong sparks and shocks due to self-induction.These experiments by Henry were published in 1835.During that same year, and following the path of Henry’sexperiments, P ro essorf C. G. Page of Washington made upsimilar coils on which connections or taps were made at in-tervals throughout their length. Page found that when abattery circuit was made or broken through any two ofthese connections, sparks could be obtained through anyother pair of connections. This arrangement was in effectan autotransformer.

INDUCTION COILSThe Reverend N. J. Callan of Maynooth College in Irelandconstructed an electromagnet, as he called it, a descriptionof which was published in 1836. It had a horseshoe-shapediron tore upon which he wound two coils of wire, one uponthe other. The inner coi1 was of heavy copper wire 50 feetlong, and the outer coi1 was of fine iron wire 1300 feetlong, each turn insulated from its adjacent turns. The twocoils were connected and a tap was brought out from thejunction between the coarse and fine wire coils.

Callan found that by making or breaking a battery circuitthrough the inner coi1 strong shocks could be obtainedfrom the outer coil. In the same year Callan constructed amuch larger coi1 with two entirely separate windings, ofwhich the inner one was copper wire ‘/binch in diameter,and the outer one also copper wire ‘/40 inch in diameter and10,000 feet long. He provided this coi1 with an interrupter

Alternating Currents 179

to produce an intermittent current. This coi1 producedsparks of considerable length. In 1837 Callan made severalcoils with separate primary and secondary windings, and hewas able to increase the effect by connecting the secon-daries of several such coils in series.

In the same year Sturgeon wound a double coi1 on a hol-low wooden spool into which he inserted iron cores. Profes-sor C. H. Bachhoffer, in working with a similar coil, dis-covered that a tore made up of a bundle of iron wires gavemuch better results than a solid iron tore.

Page made several two-winding induction coils in 1838,using iron wire cores and magnetic interrupters. Page as-serted that he had used iron wire cores before February1838, SO that there is some uncertainty as to whether he orBachhoffer deserves the credit for the invention. The inter-rupter used on these coils was Page’s invention. It was ac-tuated by the magnetism in the tore and the break wasmade in mercury cups.

Wagner and Neef made a modification of Page’s inter-rupter in which platinum contacts were substituted for themercury cups. MacCauley of Dublin may, however, havemade a similar interrupter at an earlier date than Wagnerand Neef.

In France Masson and Bréguet began to make inductioncoils of excellent workmanship in 1838. With them theycharged Leyden jars and produced luminous discharges inevacuated tubes. Similar experiments had, however, alreadybeen performed by Page.

H. D. Ruhmkorff of Paris began making induction coilsabout 1851. He was famiiiar with the work of Masson andBréguet, and others who had already produced powerfulcoils. One of these built by Page in 1850 gave a spark of8 inches. Ruhmkorff was an excellent craftsman, and made

from the primary winding.Fizeau, whose fame is due chiefly to his work with light,

discovered in 1853 that the performance of an inductioncoi1 was greatly improved by connecting a condenseraround the points of the interrupter. Such a condenserserved to absorb the self-inductive discharge from the pri-mary and made the break more abrupt. It served also toreduce the burning of the points by minimizing the spark atthat contact.

Ruhmkorff adopted the condenser and made many im-provements in various details, SO that his coils were prob-ably the finest made anywhere. He engaged in their manu-facture on a large scale and was therefore often consideredas the inventor of the induction coil. One of his largest coilsmade in 1867 gave sparks of 40 centimeters, or about16 inches.Another Parisian, named M. Jean succeeded in obtaining a

30-inch spark by immersing his coi1 in turpentine. It is pos-sible however that Poggendorff may have originated the ideaof oil immersion. Poggendorff improved the condenser byusing mica in place of oiled silk or paper. He studied care-fully the proportions of coils that give the best results andthe size of condenser required for coils of different sizes.

Other important coi1 makers were Storer of Germany,Apps and Grove of England, and Ritchie of the UnitedStates. Ritchie made a coi1 in 1860 that gave a spark of53 centimeters. The most famous coi1 was one built byApps for Mr. Spottiswoode, known as the Spottiswoode

Alternating Currents 181

coil, which gave a spark of 42 inches, or nearly 107 centi-meters.

Sir William Grove used alternating current from a smallmagneto machine to excite an induction coil. Up to thistime the magnetic circuits of induction coils were open.The cores, except those of Callan, were almost invariablycylindrical in form. In 1856 C. F. Varley obtained a Britishpatent for an induction coi1 with a closed magnetic circuit.The iron wires that made up the tore were considerablylonger than the coil. When the coi1 had been completelywound and insulated, these wires were bent back over thecoi1 from both ends SO as to encase it completely, and werethen firmly secured by bands.Jablochkov had applied for a patent in 1877 for a coi1 to

be used in connection with his arc lighting system in Paris.British patents were issued in 1878 to H. Wilde, C. W. Har-rison, C. T. Bright, J. B. Fuller, and de Meritens for induc-tion coils, or transformers to be used for purposes such aslighting and telegraphy. Marcel Desprez and Jules Car-pentier in France proposed in 1881 to use an induction coi1to raise the potential at the generator for transmission to amore distant point and then to use a second induction coil,with connections reversed, to reduce the potential to avalue suited to the purpose for which the energy was to beused. This proposa1 seems to have been the first to stateclearly the use of transformers as we now know them.

GAULARD AND GIBBS

Gaulard and Gibbs began work in England in 1882 on theapplication of induction coils, or transformers, or sec-ondary generators as they called them, to long circuits forlighting. Their original coils had straight cylindrical cores ofsolid iron. They were used on series circuits with the pri-

energy for a group of incandescent lamps, and the otherlighted several Jablochkov candles and incandescent lampsand also operated a small motor, probably a series com-mutator machine. Later in 1883 Gaulard and Gibbs madean installation along the Metropolitan Railway in London.Current was sent over a series circuit 16 miles in lengththrough four transformers that served incandescent and arclamps at four of the railway stations.

At an exhibition held in Turin in 1884, they set up acircuit 50 miles in length with four of their secondary gen-erators along the route. Each of these served a group of arcand incandescent lamps. Gaulard and Gibbs were refused aBritish patent but were granted a United States patent in1886. Their transformer had before this time been rede-signed with a closed laminated magnetic circuit.

In the meantime, during the year 1885, Zipernowsky,Déri, and Blathy of Budapest exhibited a pair of trans-formers in London with closed magnetic circuits. Thesewere operated at 1000 volts on the primary side and100 volts secondary. Other more or less successful trans-formers with closed magnetic circuits, had been producedby Rankin, Kennedy, and Hopkinson.

William Stanley had been experimenting with transform-ers, which he called converters, during the years 1884 and1885. In the latter year, working independently of develop-ments abroad, he set up a circuit at Great Barrington, Mas-sachusetts, which included an alternator, a %-mile line, anda transformer, from which he operated 150 16-candlepower

Alternating Currents 183

lamps. Stanley’s transformer was of the shell type; that is,the iron tore to a large extent encircled the windings. Thetore was made of sheet iron stampings, suitable for manu-facturing processes.

WESTINGHOUSE ALTERNATING-CURRENT SYSTEM

George Westinghouse had been watching the developmentof the alternating-current system with great interest and in1885 purchased the Gaulard and Gibbs rights in the UnitedStates. He engaged William Stanley to work on rhe problemand to design a transformer that could be produced inquantities by ordinary manufacturing processes. The West-inghouse Company began the manufacture of alternating-current apparatus within a short time, including transform-ers, generators, and auxiliary equipment. The first large-scaleinstallation was made in Buffalo in 1886. In the followingtwo years a great many alternating-current installationswere made by the Westinghouse Company in many citiesthroughout the United States.

There was considerable opposition to alternating currents,especially by the Edison Company, based on the fact thathigh voltages were employed, which it was said were verydangerous, a s they p r o b a b l y w e r e at the t ime . TheThomson-Houston Company hesitated for several years,and then in 1888 brought out a competing alternating-cur-rent system. Professor Thomson had experimented withtransformers while he was still teaching at Central HighSchool in Philadelphia in 1879 and had delivered severallectures on the subject.

ALTERNATING-CURRENT GENERATORS

Little has been said about alternating-current generators.They developed quite naturally from the direct-current

mostly slow-speed steam engines, and even though genera-tors were belted, their speed was still slow. The speed ofdirect-current machines was kept low for another reason. Inthe early days, brush and commutator troubles were amongthe greatest difficulties experienced by the operators, andthese troubles were greatly exaggerated at higher speed.When the carbon or graphite brush was introduced, some ofthe difficulties disappeared.

FREQUENCIES

Freyuencies at first were generally rather high; 133 cycleswas common. With the coming of the induction motor,however, it was found that lower frequencies were far moresuitable for power. Because of these conflicting require-ments the matter of frequencies was for a time in a chaoticstate. Gradually the higher frequencies disappeared andmost systems settled down to 50 or 60 cycles for lightingand 25 cycles for power, but there were some exceptions.

AC-DC CONVERSION

Most electric utilities started out with Edison or direct-cur-rent systems in their business sections, but as the demandfor electric service for residential use developed, alter-nating-current systems were built to serve the more distantcustomers. These alternating current systems at first weresingle phase and were later replaced by two- or t,hree-phase

installations.With this combination of direct- and alternating-current

Alternating Currents 185

systems, it became desirable to shift the load from one totbe other. For this purpose the rotary converter was thesimplest answer, but with the knowledge then availablerotary converters for the higher frequencies were impracti-table because of the high commutator speeds. It was notuntil about 1905 that 60-cycle rotary converters were intro-duced. Until that time tbey were used on 25-cycle orslightly higher frequencies, and motor-generators were usedat higher frequencies.

Street railway systems were changing from horse-drawn toelectric traction during the late 1880s and the early 1890sunder the leadership of Siemens and Hopkinson in Europe,and Edison, Sprague, Van Depoele, Bentley and Knight,and others in the United States. The advantages of alter-nating current generation, transformation, and transmis-sion, with conversion equipment in substations at variouspoints soon became apparent. Here also, the lower frequen-cies were necessary because of the limitations of conversionequipment. In many cases the railway companies’ equip-ment was more modern than that of the electric utilitiesbecause the railway companies had the advantage of tbeexperience gained by the electric companies.

ALTERNATING-CURRENT MOTORS

The direct-current motor was already well established whenthe alternating-current system came upon the scene. Seriesmotors sometimes operated on series arc light circuits, andshunt or compound-wound motors were used on the incan-descent systems. It was found that some of the series mo-tors performed tolerably well on alternating current, but atreduced capacities.

A form of induction motor was described by F. C. Baileyin 1879. Professor Galileo Ferraris of Turin, Italy, devel-

I 1

before a meeting of the American Institute of ElectricalEngineers, his invention of the induction motor. GeorgeWestinghouse realized immediately the value of the newmotor and acquired forthwith not only Tesla’s inventionbut also his services. Putting the new motor into com-mercial service was not without its difficulties. The earlyalternating-current systems were single-phase, 133 cycles-too high for a motor. The self-starting single-phase motorwas not available at first, and without two- or three-phasecircuits, the induction motor was useless.

The coming of the induction motor, therefore, made nec-essary the overhaul and redesign of much of the existingapparatus and the scrapping of many machines only two orthree years old.

NIAGARA FALLS DEVELOPMENT

There were widespread effects from the development of analternating-current motor, most important of which was thepower development at Niagara Falls. The original charterfor power at Niagara Falls was granted in 1886. It wasplanned at that time to construct a tunnel to receive thewater discharged from hydraulic turbines located at variouspoïnts in the city of Niagara Falls and discharge this waterat a point below the falls. Industrial sites were to be pro-vided along a canal from which each lessee would take thewater for which he contracted and discharge the tail waterfrom his turbines into the tunnel.

Alternating Currents 187

Although the generation of electricity had been con-sidered, no serious thought had been given to convertinglarge amounts of waterpower into electrical energy. Theproject was under discussion for several years, and manysolutions were offered, including the transmission of powerby compressed air. Fortunately the development of alter-nating-current apparatus had progressed sufficiently by thistime SO that its use was considered practical. The solutionfinally adopted, after bitter debate and with considerabledoubt and misgivings by many, was the plan offered byProfessor George Forbes, which called for the installationof polyphase alternating-current generators.

Work on the project was begun on October 4, 1890. Thecontracts for electrical equipment were awarded to theWestinghouse Company, and called for three 5000-horse-power, three-phase, 25-cycle, 2200-volt machines. This con-tract was let in October 1893, with delivery in about a year.Considering the fact that these were the largest machinesbuilt up to that time, and considering also that these werevertical machines in which the entire weight of the rotorwas suspended from the top bearing, it was an engi-neering accomplishment of the first order. The first powerwas delivered in August 1895, and the first customer wasthe Pittsburgh Reduction Company, which later became theAluminum Company of America. This company producedaluminum hy the Hall process, which had been discoveredin 1886. Operation of the first installation was eminentlysuccessful, and within a short time seven additional genera-tors were installed in Power House No. 1.

TRANSMISSION LINES

In the year 1891 a notable achievement was recorded inGermany with the construction of a llO-mile three-phase

about 1892 at 5000 volts, and from San Antonio, Califor-nia, to San Bernardino, also in 1892, 28 miles, with a15-mile tap to Pomona. This second line operated at10,000 volts single-phase.

The succcss of these early lines encouraged the engineersat Niagara to undertake the transmission of power to Buf-falo in 1896. The first line was 22 miles in length and oper-ated at 11,000 volts, three-phase. After Power House No. 1,with a capacity of 50,000 horsepower, had been completed,Power House No. 2, with an identical 50,000 horsepower,was begun, but the electrical contracts were awarded to theGeneral Electric Company.

Following the success of the Niagara Falls development,power companies throughout the country began the instal-lation of two- and three-phase systems to replace the now-outmoded single-phase equipment. Other large-scale hydro-electric developments followed close upon the heels of theNiagara Falls installation.

FREQUENCY AND VOLTAGE STANDARDS

Because the electrical age had corne SO suddenly there wereas yet no generally accepted standards. Not only were theredirect- and alternating-current systems, but there were manyvoltages, two-phase and three-phase, 25 cycles, 35 cycles,50 cycles, 60 cycles, and many types of equipment thatwere often incompatible with other equipment. With thepassage of time direct current has almost disappeared;60 cycles has become standard in the United States; volt-

Alternating Currents 189

ages are generally multiples of 115, although 120 volts hasbecome more common for residential service; and manu-facturers have adopted standards that make most types ofequipment interchangeable. Similar changes have takenplace in most other countries, except that in some Euro-pean countries 50 cycles is the standard frequency, and220 volts is in common use on lighting circuits.

wagons, coaches, barges, sailboats, and steamboats. Over-land transportation was limited until canais were con-structed to link up with natural waterways.

RAILS AND RAILWAYSFor some purposes it was found to be desirable to providerails made of timber or stone to guide the wheels of wagonsor carts. Some used flanged wheels riding on rails consistingof iron straps screwed to wooden stringers, and later ironrails attached to wooden ties were used. Installations of thissort became common around mines, quarries, and sawmills.The cars were sometimes drawn by horses, sometimespulled by tables, and in other cases pushed by men.

When the construction of the Liverpool and ManchesterRailway had been nearly completed in 1829, the directorswere undecided as to whether the motive power was to bethe horse, the steam-driven table, or the steam locomotive.George Stephenson finally proved that his steam loco-motive was the most satisfactory method of propulsion.The steam locomotive proved its value, and from that timeforward steam railroads were built in ever-increasingnumbers.

STREET RAILWAYSFor urban transportation the horse-drawn coach oromnibus was widely used in larger cities and for interurbanjourneys. Construction of the first street railway, or tram-way, was begun in New York City in 1832. The cars were

Electric Traction 191

home-drawn, provided with flanged wheels, rolling on ironstraps screwed to wooden stringers. Operation of this linewas begun in 1833, but the project soon failed due to lackof patronage. A similar project was undertaken in Boston in1836. A second attempt was made in New York City in1852, using grooved iron rails laid on timber stringers. Thisform of rail proved to be troublesome because it caught thecarriage wheels. In Philadelphia, a step rail was used on astreet railway in 1855 with somewhat greater success. Thefirst British tramway was built at Birkenhead in 1860. Be-tween 1860 and 1890, home-drawn street railways wereconstructed in a11 of the larger cities of the United States,and a somewhat similar development occurred in Europebut at a slower rate, due, in part, to the many narrow,winding streets.

The first elevated railroad began operation in New YorkCity in 1867. Motive power at first was supplied by a table,but a short time later steam locomotives were substituted.This project, as was the case with the first surface line,became involved in financial troubles but was reorganizedand continued to operate. Other elevated lines were built inNew York City, and eventually a11 of these were con-solidated into one system.

In some instances the steam locomotives built for use onthe elevated lines were used on surface lines. These werenot the same as those in use on main line railways but werelighter and resembled the cars in the train that they pulled.Such applications of steam locomotives were confinedlargely to interurban lines, where greater speed was re-yuired.

ELECTRIC PROPULSIONHorsecars, for a time, seemed to solve the public transporta-tion problem, but they were slow; and as the cities grew in

tion with his electric motor, built a small electric car whichhe operated on a circular track at Springfield, Massachu-setts, in 1835. Robert Davidson of Scotland, in 1838, builta five-ton car propelled by an electric motor of his owndesign.

In 1847 Moses G. Farmer, whose name is already familiarbecause of his early experiments in electric lighting, con-structed and operated an electric car capable of carryingtwo passengers. Professor C. G. Page of Washington made atriai run of a small electric locomotive on the Baltimore andOhio Railroad, between Washington and Bladensburg in1851. The motor was of the walking-beam type.

These and other experiments with electrically operatedcars were interesting, but none of them was practical be-cause the motors were inefficient and the batteries used forpower were much too expensive. After the dynamo hadbeen brought to a reasonable state of perfection and hadbeen found to be reversible, electric power for traction andother purposes took on an entirely different aspect. At theindustrial exposition in Berlin in 1879, Dr. Werner Siemensexhibited and operated an electric locomotive and cars overa circular track about 900 feet long, with power suppliedby a dynamo. The motors on the locomotives for the firsttime were commutator-type machines, which were capableof a steady and powerful pull. Current was suppliedthrough a third rail.

Two years later, in 1881, Dr. Siemens built an electricrailway at Lichterfelde, a suburb of Berlin, as a regular

Electric Traction 193

commercial ventrue. This electric railway went into opera-tion in the spring of 1881 and continued to carry passen-gers regularly thereafter.

Following Siemen’s demonstration, numerous similar rail-ways were built. Applications for electric railway patentsfiled in the United States Patent Office by Thomas Edisonand Dr. Werner Siemens in 1880 were denied because of acaveat filed by Stephen D. Field in 1879. The Field andEdison interests were, however, pooled, and a companycalled the Electric Railway Company of the United Stateswas formed. Edison built a small experimental electric rail-way at Menlo Park in 1880 and another in 1882. Field alsobuilt an experimental electric railway at Stockbridge, Mas-sachusetts.

At the Chicago Railway Exposition held in 1883, the Elec-trie Railway Company of the United States exhibited anelectric railway. A third rail was used for this project, aswas the case in the earlier Siemens exhibit, and the railjoints were bonded with heavy copper wire. Both the motorand the dynamo had been manufactured by the WestonCompany.

ELECTRIFICATION OF STREET RAILWAYS

These demonstrations had shown that electric tractioncould become successful, and as a result street railway com-panies became deeply interested in electrification. Therewere many objections to horsecars and table cars, the mostimportant of which was that they were too slow. Citieswere spreading out, and there was great need for movinglarge numbers of people from their homes to their places ofemployment.

In the United States those who became most active in thisfield, after Edison and Field, were Frank J. Sprague,Charles J. Van Depoele, Edward M. Bentley, Walter H.

,able to Edison. After the installation of the Edison systemat Brockton, Massachusetts, Sprague was put in charge. Hecontinued his work with Edison but also devoted consider-able time to his own research on the electric motor. Hesucceeded in designing an excellent motor and at the sametime began to take a serious interest in electric railways. InApril 1883 he resigned from Edison’s organization and inNovember 1884 organized the Sprague Electric Railwayand Motor Company.

Van Depoele, who was a skilled cabinetmaker and wood-carver, came to Chicago from Belgium in 1869. He built upa successful business and with his surplus funds began toexperiment with electrical equipment. Within ten years hewas installing arc lighting systems of his own manufacture,and in 1880 the Van Depoele Electric Manufacturing Com-pany was established in Chicago. At about this time hebecame interested in electric railways, and in 1884 ex-hibited an electric railway in Toronto, which was equippedwith overhead trolley wires. He received a United Statespatent covering this system a short time later, over theprotests of Sprague, who had also invented overhead trol-leys but was out of the country at the time.

Leo Daft installed and operated the Saratoga and MountMcGregor Railroad in 1883, using electricity for motivepower. Later he electrified one of the New York elevatedlines.

Knight and Bentley, who were employed by the BrushElectric Company at Cleveland, developed an electric trac-

Electric Traction 195

tion system that operated successfully. Their first experi-mental car was put in service on one of the Cleveland lineson July 26, 1884. Although the car was kept in operation,the difficulties encountered were enormous. They experi-enced troubles with the motor suspension, the main driveto the axles, the central station generators, the motors, andother equipment. Valuable experience was gathered, how-ever, and one by one the problems were solved. Theyabandoned the Cleveland experiment in 1887 and moved toWoonsocket, Rhode Island, where they had a contract withthe street railway company for the electrification of thesystem. Equipment for this project was supplied by theThomson-Houston Company. The first car on the Woon-socket lines was put in service in October 1887.

Knight and Rentley entered into another contract with theObservatory Hi11 Passenger Railway Company of AlleghenyCity, Pennsylvania. This project involved problems that hadnot been encountered previously, such as a 12 percentgrade on a Sharp curve. The work was completed in spite ofthe difficulties, and the first car was placed in service inJanuary 1888. The problems that followed, for a time,seemed almost insurmountable. The motor brushes werelaminated copper, and sparking was SO severe that brushesand commutators were sputtering and burning up in rapidsuccession, leaving a trail of copper along the entire route.

The Sprague Electric Company undertook the electrifica-tion of the Richmond, Virginia, street railway system in1887. After many construction difficulties, and after a caseof typhoid fever, Sprague succeeded in getting portions ofthe electrified system into operation late that year. TheRichmond undertaking was the most ambitious SO far, inthat it involved more miles of track, more cars, and manygrades, some of which were steep.

Depoele, who was then associated with the Thomson-Houston Company, recalled that he had once tried a carbonbrush on a small motor and it had appeared to work satis-factorily. No one believed that a carbon brush with its highresistance could overcome the difficulties in railway mo-tors, but the situation was SO desperate that anything wasworth a trial. Carbon brushes were tried and they worked.Not only did the brushes no longer burn up, but the com-

Figure 13.1 Sprague Electric Car (Courtesy General Electic Com-PanY)

Electric Traction 197

mutators took on a polished, dark brown appearance. Whencarbon brushes were substituted for copper and brass onthe railway motors, peace and tranquillity settled downupon the sorely harassed railway shops.

RAPID CONVERSION FROM HORSECARS TOELECTRIC PROPULSION

From that point forward electrification of the street rail-ways of the United States proceeded at a pace that taxedthe ability of the manufacturers to supply the neededequipment. There was, of course, a steady evolution in mo-tors, cars, control equipment, rails, roadbeds, overhead con-ductors, and power supplies. Among the important develop-ments were the series-parallel controller, interpole motors,alternating-current distribution systems with rotary-con-verter or motor-generator substations, heavier rails, newmethods of bonding, and higher speeds.

SUBURBAN AND MAIN LINE ELECTRIFICATIONThe electric street railways developed into interurban lines,elevated railways, subway lines, and main line railways.Mention should be made also of trackless trolleys, whichwere buses equipped with electric motors fed from a doubleoverhead trolley wire through a swiveled trolley pole.

THE DECLINE OF ELECTRIC STREET RAILWAYS

There are very few electric street railway systems remainingin the United States because of the lower cost and greaterflexibility of buses powered by interna1 combustion en-gines. In Europe, however, where the automobile has notmade such great inroads on the numbers of passengerscarried, electric street railways are still operating success-fully.

In the one hundred years between the closing decade of theeighteenth Century and the late nineteenth Century, elec-tricity had progressed from a little-known, mysterious,natural phenomenon to a well-established science of greatpractical value. It had moved from the laboratory and lec-ture room into industry and commerce, where it touchedthe lives of all. The first giant step was taken by Volta,followed by Davy, Oersted, Faraday, Henry, Pixii, Ber-zelius, Ohm, Weber and Gauss, Ampère, Coulomb, Morse,Wheatstone, Swan, Edison, Bell, Maxwell, Helmholtz, and ahost of others. The exploration of nature’s great house hadindeed progressed at an amazing rate, but there were manydoors that had not yet been unlocked. What lay beyondone of these had been guessed by Faraday, Henry, andMaxwell, but the key was found by a Young German profes-sor named Heinrich Hertz (1857-1894).

HERTZ DISCOVERS ELECTROMAGNETIC WAVESHertz, as a Young man, had been an assistant to the greatHelmholtz at Berlin. The researches of Helmholtz and themathematical explorations of Maxwell had convinced himthat certain electrical phenomena are accompanied by elec-tromagnetic waves in space. In 1887, at the age of thirty,when Hertz was professor of physics at the TechnischeHochschule in Karlsruhe, he succeeded in proving the exis-tence of such waves by means of rather simple apparatus.He set up a circuit containing an induction coil, a wire loop,and a spark gap. At the other end of the table he had a

Electromagnetic Waves and Radio 199

similar circuit containing only a spark gap. A dischargefrom the induction coi1 across the first gap was accom-panied by a weaker spark across the gap in the receivingcircuit. In order to prove that this experiment did indeeddemonstrate the existence of electrical waves, he carried onfurther experiments for several years, and succeeded in re-flecting and refracting these waves and in measuring theirwavelength. Joseph Henry, many years earlier had nearlysucceeded in proving what Hertz had found but had fallen alittle short. He had even spoken of the phenomenon asresembling waves. Faraday had demonstrated that a mag-netic field rotated the plane of polarization of light waves,and Hertz proved that electromagnetic waves were not lim-ited to the very short ones. Maxwell’s mathematical geniushad been vindicated.

SIGNALING WITHOUT WIRES

As has been SO often the case, great discoveries have beenanticipated by others. In Galvani’s first frog experiment anelectrical impulse had been transmitted from an electricalmachine to a scalpel without wires. Morse performed anexperiment in 1842, in which he buried two plates in theground on one side of a canal, connected through a batteryand a key, and on the other side he buried two similarplates, connected through a galvanometer. He succeeded intransmitting signals by means of this equipment, but theresults here were due merely to conduction.

Using somewhat similar equipment, Alexander GrahamBell performed experiments of the same kind on boats onthe Potomac River in 1882 and succeeded in sending signalsup to 1% miles.

Edison, working with Gilliland, Phelps, and Smith in1885, was able to establish communication between a

installed on the Lehigh Valley Railroad in 1887 and oper-ated successfully. The results were regarded at the time asmerely the effects of induction, but the system certainlycontained some of the elements of radio telegraphy.

GUGLIELMO MARCONIHertz and his colleagues were not greatly impressed withthe importance of the discovery of electromagnetic waves,but others began to see the possibility that there could bepractical applications for this newly discovered phenome-non. Near Bologna, Italy, a Young man only twenty yearsof age, named Guglielmo Marconi (1874-1937), began in1894 working with apparatus similar to that used by Hertz,with the definite purpose of using electromagnetic wavesfor communication without wires.

Marconi had one great advantage over Hertz because ofthe invention in 1890 by Branly of Paris of a device called acoherer. Branly had discovered that when certain metalfilings were subjected to high-frequency alternating currentstheir direct current conductivity was thereby increased.Marconi found that the coherer could be used as a detectorfor electromagnetic waves. He was able to improve uponBranly’s original invention by using silver plugs in a glasstube with a small gap between them which was filled with amixture of silver and nickel filings.

Marconi was not alone in his search for a method of wire-less communication. A Russian named Alexander S. Popov

Electromagnetic Waves and Radio 2 0 1

described his wireless telegraph apparatus before a gatheringof the Russian Physical Society in St. Petersburg in 1895.His equipment was very similar to that which Marconi wasusing and included a coherer as a detector. Popov claimedthat he had sent a wireless signal a distance of 600 yards.Because of Popov’s address before the Physical Society theRussians have claimed priority over Marconi. Whatever themerit of these claims it was Marconi who developed thewireless telegraph into a practical reality.

FIRST RADIO PATENT

During the year 1895 Marconi was able to transmit wirelessmessages over a distance of a mile. He received a Britishpatent in 1896. In 1897 a group of wealthy Englishmen, atthe suggestion of Sir William Preece, head of the BritishPost Office, formed a company called the Wireless Tele-graph and Signal Company, which gave Marconi about

&60,000 in stock and &15,000 in money for the use of hisinvention and retained him to carry on further experiments.By the year 1900 wireless signals were transmitted a dis-tance of 200 miles, and on December 12, 1901, Marconireceived a wireless signal at St. John’s, Newfoundland,which had originated at Poldu in Cornwall, England.

Many improvements were introduced as the result of yearso f experimentation, including improved antennas and farmore sensitive detectors. Marconi’s first detector was thecoherer. For his transatlantic transmission in 1901, he usedthe mercury detector that had been invented a short timebefore by Lt. Solari of the Italian navy. Various forms ofdetectors had been invented over the brief early period ofwireless telegraphy, including those already mentioned plusthe electrolytic, the magnetic, and the hot-wire.

volving high frequencies. Joseph Henry may have had someinkling of the need for tuning two circuits to respond to thesame frequency. Multiplex telegraphs had made use oftuning at lower frequencies in order to separate the differ-ent messages coming over the same line. When Marconiapplied this principle to wireless telegraphy, he achievedsuccess. He was granted a patent on tuned wireless circuitsthat for many years was the basic patent in that field.

CONTINUOUS WAVESThe spark used by Marconi for his wireless telegraph pro-duced a series of damped waves on a broad spectrum. Sucha signal would be strongest in the region of the naturalfrequency of the transmitter circuit but would includemany strong harmonies on both sides of the fundamental ornatural frequency of the circuit. Each spark caused a groupof electromagnetic waves of different frequencies that de-cayed to zero very quickly followed by another burst andanother, at a rate determined by the interrupter on the coil.The effect on the receiver was a tone determined by thefrequency of the interrupter. This tone was broken intodots and dashes by the key of the sender.As early as 1892 Professor Elihu Thomson had discovered

that a direct-current arc could produce undamped electricaloscillations. W. B. Duddell of England discovered in 1900what was called the singing arc. Valdemar Poulsen of Den-mark applied the discoveries of Thomson and Duddell toproduce high-frequency oscillations for use in radio trans-

Electromagnetic \I aves and Radio 203

mitters for which he received a patent in 1903. Fessendenused the Poulsen arc a short time later for wireless transmis-sion. Despite the development of the Poulsen arc, mostwireless stations were still using spark transmitters, but theyhad been greatly improved in the meantime SO that interfer-ence was diminished considerably.

Poulsen formed his own company in 1910, and in thesame year the Federal Telegraph Company bought his rightsfor the United States. The United States Navy adopted thePoulsen arc transmitter in 1912 or 1913 and used it untilthe end of World War 1. The German Telefunken beganusing a form of arc transmitter as early as 1906, and Ger-many was therefore further advanced in wireless transmis-sion than Hritain or the United States.

DETECTORS

The principal forms of detectors in the early period of radiodevelopment were coherer, mercury, magnetic, hot-wire,electrolytic, and crystal. The coherer and mercury detectorwere mentioned earlier in connection with Marconi’s work.It is rather surprising that a number of kinds of detectorshad been invented before there was any serious effort atwireless communication. An early form of magnetic detec-tor was devised by Ernest Rutherford in 1895. Marconimade two improved forms of magnetic detector in 1902.Altogether there were about a dozen forms of this type ofdetector.

R. A. Fessenden of the United States invented the elec-trolytic detector in 1902, and W. Schloemilch of Germanydiscovered the same principle a little later. The hot-wiredetector goes back to the year 1890 when Rubens andRitter made suc11 a device in the form of a Wheatstonebridge. Fessenden received a U. S. patent on an improved

also, General Dunwoody of the United States Army foundthat a combination of carborundum and carbon made a verystable detector. Many other crystals were found to be gooddetectors especially galena, which is lead sulfide. AfterWorld War 1, and especially after broadcasting was begun,amateurs built crystal receiving sets in great numbers.

THE EDISON EFFECTEdison had noted the blackening of his light bulbs in theplane of the filament and particularly near the positiveterminal. In trying to find the reason for this phenomenonhe had provided one of his lamps with a small plate insidethe bulb near the filament that was connected to a lead-inwire. He found that a galvanometer connected to this plateand to the filament showed a small current, when the lampwas in operation, and that the plate was negative with re-spect to the filament. He discovered also that when a bat-tery was connected to the filament and to the plate, acurrent could be made to flow in one direction but not inthe other. He noted also that when the battery voltage wasincreased sufficiently, a blue glow appeared around the fila-ment. The phenomenon, relating to the conductivity of theevacuated space in the lamp, called the Edison effect, wasdiscovered in 1883 and was patented by Edison.

Elster and Geitel in Germany began an investigation in1882 of ionization caused by incandescent metals. Aboutthe year 1888 they carried out experiments with evacuatedbulbs and rediscovered the Edison effect. Hittorf found in

Electromagnetic Waves and Radio 205

1884 that the space between hot and cold carbon elec-trodes was partially conducting.

THE FLEMING VALVE

William H. Preece, who was at the head of the British tele-graph service, about 1888 conducted a series of experi-ments with an Edison bulb containing a plate, in which heverified Edison’s discovery. Similar experiments by J. A.Fleming about the year 1890 yielded the same results, con-cerning which he read a paper before the Royal Society inthe same year and another in 1896.

It was during this period that the discoveries of MmeCurie, J. J. Thomson, William Crookes, Rutherford, Lenard,Planck, and others were being made. J. J. Thomson in 1897discovered and identified the electron, which he called acorpuscle. These discoveries served to clarify some of themysteries surrounding the Edison effect, the Crookes tube,ionization of liquids, and the spontaneous emissions fromcertain elements.

Fleming’s interest in the Edison effect was revived as aresult of the new discoveries and because of the Marconiexperiments. Realizing that what was needed for the wire-less telegraph was a more efficient detector, he set aboutthe task of adapting the Edison bulb to this purpose. Hemade bulbs in which a part of the filament was surroundedby a metal cylinder connected to a separate terminal. Thisdevice, called the Fleming valve, served as a detecfor andrectifier, but as a detector it was very little better than acrystal. The Fleming valve was brought out in 1904 and wascovered by a patent.

DE FOREST AUDIONLee De Forest of the United States, who had been investi-gating the conduction of electricity through gases since

Figure 14.1 Fleming Oscillation Valves (Courtesy Bumdy Li-brary)

1900, was also working on the Edison effect and wirelessdetectors. He filed patent applications for two-elementtubes in November 1904 and in January, February, andApril 1905. These tubes had two plates or wings. On Octo-ber 20, 1906, before a meeting of the American Institute ofElectrical Engineers held in New York, De Forest made hisfirst announcement of the invention of the three-elementtube containing a grid. He called his triode tube the “au-dion,” but he apparently had no notion at the time of whata giant this new tube was to become. TO him it was merelya wireless detector, by far the most efficient S O far dis-covered.

AMPLIFICATIONIn 1911 Lieben, Reisz, and Strauss of Austria were granteda French patent covering the use of triode tubes as ampli-

Electromagnetic Waves and Radio 2 0 7

fiers. These were connected through transformers SO thatthe plate of the first tube was connected to the grid of thesecond, and SO on.

ARMSTRONG3 OSCILLATOR TUBEIn the year 1912 a Young mari twenty-two years of age,then a student at Columbia University, made a discoverythat again completely transformed wireless communicationand made possible most of the progress which followed.The Young man was E. H. Armstrong, and the discoverywas the fact that when suitable connections were madefrom the grid of a tube to its plate the tube would oscillateand would generate high-frequency alternating currents thatcould be used as the source of continuous electric waves.

De Forest made the same discovery at about the sametime, but Armstrong was given priority, although his patentwas not filed until October 29, 1913. Besides Armstrongand De Forest, it appears that Round and Franklin in En-gland and Meissner in Germany had approached veryclosely to the same discovery at about the same time.

The European war began in August 1914, and radio be-came a matter of great military importance. New develop-ments in radio came very rapidly but were often cloaked ingreat military secrecy. The radio telephone soon came intouse for ship to ship, and ship to shore communication, butfor long-distance work radio telegraph was still used almostexclusively. For suc11 long-distance communication thesources of electric waves were still the spark for dampedwaves, and the Poulsen arc for continuous waves.

THE ALEXANDERSON

HIGH-FREQUENCY GENERATORR. A. Fessenden had made an attempt in the early 1900s tobuild a high-frequency generator. He took his idea to the

Figure 14.2 Ernst F. W. Alexanderson with His High-FrequencyGenerator. This is the later mode1 of his alternator used in radiostations after 1918. (Courtesy General Electric Company)

Electromagnetic Waves and Radio 209

General Electric Company, where Ernst F. W. Alexandersonwas asked to find a solution. After working on the problemfor two years, he produced a small generator which couldoperate at 60,000 cycles, and a little later at 100,000cycles. The first trials of the Alexanderson high-frequencygenerators were made in 1906, with somewhat indifferentresults. Little was heard of high-frequency alternators until1918 when a 200-kilowatt machine was installed at theAmerican Marconi Company station at New Brunswick.Signals from this new station were strong and clear.

The Marconi Company offered to buy exclusive rights tothe Alexanderson generator, but the General Electric Com-pany was dissuaded from taking such a step. Finally, in1919, a new company called the Radio Corporation ofAmerica was formed under the sponsorship of the GeneralElectric Company to exploit the new device. Later theAmerican Telephone and Telegraph Company, the WesternElectric Company, the Westinghouse Electric and Manufac-turing Company, and the United Fruit Company were in-vited to participate. In 1932 RCA became an independentcorporation, and its stock was widely distributed.

AMATEUR RADIO AND RADIO BROADCASTING

When the European war ended in 1918, radio was back inprivate hands, and with the change came a wonderful newinterest on the part of amateur radio operators. Many ofthese had been radio operators in the various navies orarmies and had sufficient knowledge to build sending andreceiving sets. These amateurs were licensed by the federalgovernment and were assigned station cal1 letters. At firsttheir messages were in international Morse code, but laterthey changed to voice. Their work greatly accelerated thedevelopment of radio, especially shortwave. The amateurs

Company established the first broadcasting station in theworld, station KDKA at Pittsburgh. Within a very shorttime there were hundreds of such stations throughout theUnited States and in Europe. The American stations, how-ever, were privately owned and depended upon advertisingfor their support, whereas European stations were ownedby the various governments and expanded more slowly.

The response of the public was immediate, and almosteveryone that had any mechanical ability was building acrystal receiver equipped with headphones. A short timelater they were building single-tube receivers with powersupplied by a six-volt storage battery, and after anotherbrief period came multitube radios with amplifiers andloudspeakers. The storage battery was messy and causedacid burns in clothing, rugs, and floors. As a substitute forbatteries the manufacturers soon provided rectifiers calledbattery eliminators, but these were not entirely satisfac-tory. There was a great need for radio tubes that wouldoperate on alternating current. This need was satisfied in1926 by the invention of the alternating-current tube byH. NI. Freeman and W. G. Wade of the Westinghouse Com-

PanY.The growth of the radio industry was phenomenal. By

December 1922 there were 569 radio broadcasting stationsin the United States and an estimated 1,500,OOO to2,500,OOO receiving sets. The broadcast and other frequen-cies were soon becoming crowded SO that it became neces-sary to establish frequency bands for various purposes.

Electromagnetic Waves and Radio 211

Regulation of the radio broadcasting industry was essential,particularly in the matter of frequency allocation but alsoin the power allowed to any one station.

REGULATION OF RADIO

As early as 1910 Congress had passed the Wireless Ship Act,which set forth requirements for wireless on ships and regu-lated its use. An international conference on radiotelegra-phy, held in Berlin in 1906, had issued certain regulationsgoverning wireless that were agreed to by a11 of the impor-tant countries. In 1912 Congress passed the Radio Act,under which the secretaries of commerce and labor weremade responsible for the licensing of radio stations andradio operators. Experimental broadcasting was approved in1919 for limited commercial stations on a wavelength of360 meters.

The first National Radio Conference, held in 1922, madecertain recommendations as a result of which the secretaryof commerce issued new regulations governing broadcastingstations. These regulations provided for a minimum powerof 500 watts with a maximum of 1000 watts and permittedfrequencies between 750 and 833 kilocycles. After theNational Radio Conferences of 1923 and 1924, the Depart-ment of Commerce allocated the frequency band between550 and 1500 kilocycles to radio broadcast and permittedpower up to 5000 watts. Despite a11 attempts to tope withthe tremendous increase in the number of radio broadcaststations, regulation was falling far behind the needs of theindustry, SO that interference between stations was wide-spread, especially after sunset.

The fourth National Radio Conference, called in 1925,asked for limitations on broadcast time and station power,

the LMI-White Act of 1927, which established the FederalRadio Commission. This commission had regulatory powersover radio, including the issuing of licenses, allocation offrequencies, and the control of station power. The act alsoempowered the secretary of commerce to inspect radiostations, to examine and license radio operators, and toassign station cal1 letters.

FEDERAL COMMUNICATIONS COMMISSIONIn 1933 the secretary of commerce appointed an inter-departmental committee to study and report on the na-tional and international radio situation. The committeerecommended that a commission be established with broadpowers to regulate communications of a11 kinds. In 1934the Congress passed an act establishing the Federal Com-munications Commission, or FCC as it is generally known.Although the commission was empowered to regulate a11forms of communication, its most pressing problems werein the field of radio and television, which was just begin-ning. The new commission succeeded admirably in bringingorder into what had long been a very confused situation.The discussion here has dealt only with the United States,but the problem was worldwide, and a11 other nationsfound it necessary to adopt regulations similar to thosedescribed for the United States. From time to time inter-national agreements regulating radio were made particularlyin the matter of assigned frequencies.

Electromagnetic Waves and Radio 213

FREQUENCY ALLOCATIONS

At the present time the frequencies assigned to AM radiobroadcast lie in the band between 535 and 1605 kilocycles,and for FM broadcast between 88 and 108 megacycles,with a total of 100 channels. Certain stations are permittedto broadcast during daylight hours only, whereas otherlarge and important stations are assigned to clear channelsand 24-hour service, with power up to 50,000 watts. Cal1letters have been established by international agreement,and for the United States broadcast stations east of theMississippi, in general, have cal1 letters beginning with W,and those west of the Mississippi beginning with K. FMstations carry the suffix FM after the cal1 letters.

In addition to broadcast radio and TV the FCC has allo-cated frequency bands to a host of other applications in-cluding Safety Services (aviation, marine, police, fire, localgovernment, forestry, highway, maintenance, special emer-gency, state National Guard, and disaster), IndustrialServices (power, petroleum, forest products, business,manufacturers, relay press, motion picture, industrialradiolocation, and telephone maintenance), Land Trans-portation Services (railroad, motor carrier, taxicabs, andautomobile emergency), Amateur Radio, and CitizensRadio. In addition to these there are such other frequencybands as Government Radio, Radar, Loran, Ramark, andRadio Relay Telephone.

RADIO RECEIVERS

The improvements in radio transmitters were accompaniedby corresponding improvements in radio receiving sets andparticularly in the quality of loudspeakers. In the earlyreceivers headphones were used almost exclusively, andthey were followed by loudspeakers that were essentially

- -used by the transmitting stations, SO that by the middle1920s the quality of reception had improved tremendously.A similar improvement occurred in phonograph recordingswith the advent of electrical transcription and later with thechange from wire to tape recorders.

In addition to the improvements in the sound systemthere were equally important changes in the electrical cir-cuits of receiving sets. The early crystal and single-tubereceivers used a regenerative circuit patented by Major E. H.Armstrong in 1914. The regenerative circuit was in effect alow-power transmitter that caused howls and squeals, dueto heterodyning other receivers or transmitting stations.Heterodyning refers to the superposition of one signal uponanother of slightly different frequency resulting in a beatfrequency signal equal to the difference between the two.In 1919 Armstrong invented the superheterodyne circuitfor which he received a United States patent on June 8,1920. Some time elapsed before this circuit was fully appre-ciated but eventually it became the most widely used ofany of the circuits. Another somewhat similar circuit,which was widely used for a time, was the tuned radio-frequency circuit invented by Louis Alton Hazeltine in1924. Improvements and modifications of the superhetero-dyne circuit were made by Hartley, Colpitts, and Meissner.

At first the radio-frequency stages of receiving sets weretuned by separate knobs and required a great amount ofpatience as well as luck in tuning in a particular station. Itwas thought that it was impossible to construct the variable

Electromagnetic Waves and Radio 215

condensers and other components with sufficient accuracyto mount them on a single shaft, but this result was accom-plished after a time with the aid of small trimmer conden-sers.

One of Armstrong’s greatest accomplishments was hisinvention of the FM system of radio broadcast. In the FMsystem the frequency of the signal is modulated rather thanthe amplitude. FM .is practically free from interferencefrom static or other radio signals.

FACSIMILE TRANSMISSION

Before discussing television it Will be helpful to trace thedevelopment of facsimile transmission, which, in some re-spects, was the forerunner of television. About the year1840 Alexander Bain of Scotland invented a crude methodof sending facsimile over telegraph wires that contained cer-tain elements used in later facsimile and television, espe-cially the scanning principle. In the Bain invention, thecharacters to be sent were first set up in metal and wereconnected to one side of a battery. A pendulum carrying ametal stylus was set to swinging over the metal charactersSO that the stylus made light contact with them. The otherside of the battery and the pendulum were connected tothe line. At the other end of the line was a similar pendu-lum and stylus, which traced the characters on a chemicallytreated paper. The pendulums served to synchronize thesending and receiving apparatus. Clockwork was used atboth ends to advance the metal characters and the paper SO

as to scan successive lines. There was great difficulty, how-ever, in maintaining synchronism, and because of the cum-bersome methods involved the scheme had no practicalvalue.

lac covering a thin metal sheet and was picked up b y ametal stylus. At the receiving end the message was tran-scribed on a sheet of chemically treated paper wrappedaround a metal cylinder. Both cylinders were revolved byclockwork at the same speed, but synchronism was almostimpossible.

COMMERCIAL FACSIMILEGiovanni Caselli built an apparatus on much the same prin-ciples but with much greater mechanical refinement andoperated his apparatus commercially over a telegraph linebetween Paris and Lyons for five years from 1865 to 1870.D’Alincourt made improvements upon the Caselli devicesby using tuning forks for synchronizing. Further improve-ments were made about 1875 by Francis de Hondt ofChicago and William Sawyer of New York.

PHOTOELECTRIC DEVICESNoah S. Amstutz of Cleveland demonstrated a facsimileapparatus in 1891 in which the transmitting device con-tained a selenium ce11 and the receiver reproduced the pic-t u r e i n halftone b y means o f d o t s . T h e photoelectricproperties of selenium had been discovered by WilloughbySmith in 1873, and its applications were improved upon byShelford Bidwell, both of whom were from England.

In the late years of the nineteenth Century, Dr. ArthurKorn of Germany improved upon the Amstutz apparatus

Electromagnetic Waves and Radio 217

by introducing a selenium ce11 in the receiving set whichacted as a relay or amplifier to reinforce the incoming signaland to overcome to some extent the sluggishness of theselenium ce11 in the transmitting device. This system wassuccessfully demonstrated in 1902.

After the invention of the vacuum tube, it became pos-sible to amplify the incoming signals even more. As a nextstep the selenium ce11 was replaced by the photoelectriccell, or photocell as it is now more commonly called. In thephotocell various compounds of cesium, potassium, rubid-ium, tantalum, thorium, or zirconium were used as thelight-sensitive material. These were deposited on a metalplate that was then enclosed in an evacuated glass tube withsuitable connections to the outside. Some of the later tubeswere gas-filled The new photocells responded much morequickly to changes in light intensity and covered a greaterportion of the visible spectrum than had been the case withthe older selenium cells. Another improvement of greatimportance to facsimile was the change to synchronizationby means of alternating currents or radio signals.

PICTURES BY CABLE

H. G. Bartholomew and M. L. D. MacFarlane of Englandinvented an apparatus that made possible sending picturesby table. The impulses from the photocell were first re-corded in the form of perforations in a paper tape that wasthen fed into a standard telegraph transmitter. A similartape was made at the receiving station, which could then beput into a machine that reproduced the picture.

By 1924 the Western Union Telegraph Company was fur-nishing regular picture service to newspapers. In the sameyear RCA sent pictures by radio to Europe.

apparatus in which the sendmg station had a mosaic OIsmall selenium cells, each of which was connected by wireto a small shutter in a corresponding mosaic at the receivingstation. When an image was focused through a lens on theselenium mosaic, each ce11 responded according to the in-tensity of light falling upon it. The corresponding shuttersat the receiving end were deflected accordingly and pro-duced a crude reproduction of the original image.

THE SCANNING DISKAND MECHANICAL TELEVISION

Dr. Paul Nipkow of Berlin invented the first mechanicalscanning disk in 1884, which was the forerunner of thevarious mechanical scanners used in television transmittersfor many years thereafter. In general, it consisted of a metaldisk having a series of holes arranged in a short spiral. Asthe disk revolved at rather high speed, light impulses werereceived through the holes, scanning the various parts of thepicture to be transmitted. These momentary light impulsesfell upon a selenium ce11 that was excited in accordancewith the intensity of the light falling upon it. The small andrapidly changing electrical impulses from the selenium ce11caused a neon light at the receiving station to change itslight output accordingly. The light from the neon bulbpassed through the holes of a scanning disk like that at thetransmitter, revolving in synchronism with it. The lightcoming through the holes in the scanner fell upon a ground-

Electromagnetic \I;aves and Radio 219

glass screen and produced an image of the original picture.Television sets of this same general type with various

improvements were in operation until 1933, but none ofthese was satisfactory or commercially useful. These me-chanical television sets operated at twenty-four frames persecond, with sixty lines per frame.

THE ICONOSCOPE

Modern television had its beginning with the invention ofthe iconoscope by Dr. V. K. Zworykin, who at that timewas employed by the Westinghouse Company but who laterjoined the staff of RCA. Zworykin’s patent was filed in theUnited States Patent Office on December 29, 1923, but wasnot granted until December 20, 1938. The iconoscope wasthe essential part of the television camera and was the firstsuch device to scan a picture entirely by electronic meth-ods. The receiving apparatus, called a kinescope and nowgenerally called a picture tube, was a modification of thecathode-ray oscilloscope invented by Karl F. Braun of theUniversity of Strasbourg in 1897. In 1923, shortly after hisinvention of the iconoscope, Zworykin set up a transmit-ting and receiving station, connected by wires, operating at60 cycles, with which he was successful in transmitting tele-vision pictures.

On January 7, 1927, Ph’l F1 o arnsworth filed a patent appli-cation covering an electronic camera tube, called the dis-sector tube, which in some respects was an improvementover Zworykin’s iconoscope.

Although the essential parts and technique were at handfor electronic television, it had not yet been establishedthat electronic television was superior to the older mechan-ical equipment. On April 7, 1927, the American Telephoneand Telegraph Company demonstrated the transmission of

vision and took place between New York City and Whip-pany, New Jersey, about 27 miles distant.

IMPROVEMENTS ON THE ICONOSCOPEVarious improved forms of television tubes followed theiconoscope, beginning with the dissector tube of PhiloFarnsworth in October 1934, the emitron by John Baird inNovember 1936, the orthicon by RCA in June 1939, fol-lowed by the image orthicon and the vidicon. There weresimilarities in a11 of these, but the later tubes were muchmore sensitive and covered a greater part of the light spec-trum. Al1 of them employed a stream of electrons from anelectron gun to scan the image. This process of scanning isaccomplished with remarkable accuracy by moving the elec-tron stream from side to side and downward line by line bymeans of electrostatic and magnetic fields. In the earliertubes, including the iconscope and dissector tube, the lightfrom the scene to be televised and the electron streamimpinged on the same photosensitive surface. In the latercamera tubes the electrons are directed toward a metal sur-face in back of the light-sensitive mosaic. This mosaicscreen is made up of a deposit of microscopic globules of acesium-silver compound on a sheet of mica. Although thecoating of tiny globules appears to the naked eye to becontinuous, the individual globules are actually separatedand insulated from one another. The cesium-silver com-Pound has the property of emitting electrons when lightfalls upon it, and the quantity of electrons emitted varies

Electromagnetic baves and Radio 221

with the light intensity. When electrons are lost, the glob-ules become positively charged. In the iconoscope and dis-sector tube, there is a metal plate attached to the back ofthe mica that behaves like a condenser plate. As the elec-tron beam moves back and forth across the cesium-silvermosaic, the positive charges on the globules are partly orwholly neutralized thereby, changing the potential of theback plate and causing it to give up a tiny alternating cur-rent of high frequency. This alternating current is thenamplified and becomes the video signal.

Other types of television camera tubes operate in a similarfashion except that the electron stream strikes a plate onthe back of the mosaic, changing its potential to correspondwith the changes in potential of the globules in the mosaic.It must be remembered that each charged globule holds abound charge of the opposite sign on the metal plate di-rectly opposite its position, SO that there is a mosaic ofbound charges on the metal plate and not merely a chargeon the plate as a whole.

In the image orthicon the electron beam is reflected backto an electron multiplier that serves to amplify the signalgreatly. The image orthicon is about one hundred times assensitive as the iconoscope and cari therefore be used inordinary or subdued light, whereas the iconoscope requiredintense illumination.

TRANSMISSION BY RADIO WAVESIn order to transmit the information from the televisioncamera by radio, the carrier wave must be modulated tocorrespond with tiny impulses received by the light-sensi-tive mosaic. Transmission of the signal is complicated bythe need for sending out another signal at the same time tocarry the sound. Roth signals are sent out by the same

spects resembles the camera tube, and reproduces the pic-ture on a fluorescent screen. Synchronism between thetransmitter and receiver is maintained by means of a specialsignal at the end of each line and frame. Audio reception isof course exactly like ordinary FM reception except for thefrequencies employed.

While ordinary black-and-white television was perhaps themost sophisticated mass-produced electronic apparatusdevised up to the time of its inception, color television isfar more complex. In general, color television uses combina-tions of red, green, and blue to synthesize approximationsto the colors of the spectrum.

The camera for color television has three separate tubes,one each for the colors red, green, and blue. In the receiverthere are three scanning guns, working in synchronism,which cause the red, green, and blue phosphors to glow intheir characteristic colors.

REGULATION OF TELEVISION ANDCHANNEL ALLOCATIONS

In 1941 the Federal Communications Commission estab-lished 525 lines per frame and 30 frames per second as thestandard for the United States. Different standards exist inother countries. The FCC also allotted frequency bands inwhich the channels were separated by a minimum of 6megacycles. In the United States the frequencies allottedto television are as shown in Table 14.1.

Electromagnetic IVaves and Radio 223

Table 14.1 Frequencies of Television Channels

V H F UHF

Channel Megacycles Channel Megacycles Channel Megacycles

2 5 4 8 1 8 0 1 4 470

3 6 0 9 186 24 530

4 6 6 1 0 192 3 4 590

5 7 6 11 198 44 650

6 8 2 1 2 204 5 4 710

7 1 7 4 1 3 2 1 0 6 4 77074 830

8 3 884

The initials VHF and UHF are used to designate very highfrequency and ultra high frequency. For Channe12 thewavelength is 5.56 meters, and for Channe183 the wave-length is slightly more than ‘/3 meter.

I1.U “II”“‘XYU L”“U

No other invention or discovery in the electrical field hashad S O many important and useful descendants as theCrookes tube. From it, directly or indirectly, came theX-ray tube, the cathode-ray tube or oscilloscope, the radiovacuum tube, the iconoscope and its successors, the kine-scope, a number of accelerators, the electron gun, and theelectron microscope. The Crookes tube might properly becalled a cathode-ray tube, but that term has for some rea-son been applied to the Braun oscilloscope. The Crookestube, in addition to its importance as the ancestor of SO

many other devices, led to the discovery of radioactivity.Essentially the Crookes tube is an evacuated glass vesse1

containing a cathode or negative electrode and an anode orpositive electrode. The construction of such a tube requiresonly a skilled glassblower and a good air pump.

Glassblowing is an ancient art, but the making of chemicaland other scientific apparatus did not develop until thefourteenth or fifteenth centuries. The glassblowers of thatperiod were hampered because of the lack of gas or liquidfuels. By the nineteenth Century glassblowing was far ad-vanced, as exemplified by the work of Geissler.

Von Guericke produced the first air pump in 1654; con-structed of glass, it resembled a syringe. Similar pumps byBoyle, Hawksbee, and Smeaton had improved efficiencies.Later, still more efficient pumps, such as the oil-air pump,were made of metal. In the oil-air pump the space belowthe piston was filled with oil which served to eliminate theair that would otherwise be trapped.

Crookes Tube, Structure of the Atom 225

Figure 15.1 A Diagram of the Crookes Tube (Courtesy BurndyLibrary)

The first mercury pump was made by Swedenborg in1722, followed by mercury pumps by Baader in 1784,Hindenberg in 1787, Edelkrantz in 1804, and Patten in1824. Geissler’s mercury pump of 1855 was capable of pro-ducing a vacuum of 0.05 millimeters of mercury. Toplerimproved the Geissler pump somewhat, but the Sprengelpump of 1865 was a great improvement in that it reducedthe labor and attention required and speeded UP the rate ofevacuation. The Gaede pump of 1907 was a rotary pump,mechanically operated, which produced a vacuum of0.00004 millimeters.

VACUUM TUBES BEFORE CROOKES

The earliest experiments in vacuum tube phenomena werethose of Picard and Hawksbee. Picard observed flashes oflight in the space above the mercury in a Torricellian tubewhen the tube was shaken, and Hawksbee noted the fluo-rescence in an evacuated glass globe when it was electrified.

sure of about 2 millimeters. When a discharge from an elec-trical machine was sent through the tube, Faraday observeda purple glow near the anode and a dark space nearer thecathode. This dark space has since been called the Faradaydark space.

Masson of France, who was one of the early induction coi1makers, constructed a vacuum tube with two electrodes in1853 and discovered that when a discharge from an induc-tion coi1 was sent through the partially evacuated tube abright pink glow filled it. This phenomenon occurs with apressure of about 5 millimeters of mercury. Theoreticallythe discharge from an induction coi1 should be a pulsatingalternating current that would not be well suited for use ina vacuum tube. Actually, however, the secondary voltage isS O much higher when the circuit is broken by the inter-rupter than when the circuit is closed that the secondaryoutput is almost unidirectional.

Heinrich Geissler of Bonn made a great number of vacuumtubes that were shipped to schools, colleges, and otherlaboratories everywhere, where they were used for instruc-tion and entertainment. Most of these contained air atabout 5 millimeters of mercury and exhibited the character-istic pink glow for that pressure. Others contained gasesother than air, and some were made of glass containingmetallic salts that fluoresced in various colors.

Julius Plücker, also of Bonn, discovered in 1858 and 1859that as the vacuum is increased the Faraday dark space be-cornes larger, and he noted the greenish phosphorescence of

Crookes Tube, Structure of the .4tom 227

the glass. He also observed the effect of a magnetic fieldupon the discharge. J. W. Hittorf, one of Plücker’s students,found in 1869 that an opaque abject placed in front of thecathode cast a shadow upon the glass.

Eugen Goldstein of Germany performed a long series ofexperiments with vacuum tubes of many shapes, having avariety of electrodes. He found that the cathode rays areemitted perpendicularly to the surface of the cathode, SO

that a concave cathode would tend to focus the rays, butthe sharpness of the focus was influenced by the residualpressure and the potential difference. He found that theproperties of the rays were independent of the materialused in the cathode, and he found also that the rays couldproduce chemical reactions.

Cromwell Varley advanced the idea in 1871 that thecathode rays were negatively charged particles but withonly partial proof.

SIR WILLIAM CROOKES AND HIS EXPERIMENTS

We have very little information about Crookes’s early ex-periments with the vacuum tube that now bears his name,but it appears that he must have begun his work during the1860s because it was reported that he demonstrated hispaddle wheel experiment in 1870. In this experiment heprovided two rails inside the tube on which the axle of thepaddle wheel could roll. In this experiment the paddlewheel, which had four vanes, was made to turn by thebombardment of what Crookes later called molecular lightor radiant matter, emanating from the cathode.

Crooke’s later tubes were constructed by a skilled instru-ment maker named Gimingham and were undoubtedly thefinest S O far produced. With them Crookes carried outmany experiments that were published in several papers

228 Chapter Fifteen

Figure 15.2 Sir William Crookes (From Smithsonian Institution)

Crookes Tube, Structure of the Atom 2 2 9

delivered in 1878 and 1879. In addition to the facts alreadyknown, Crookes found that the character of the dischargechanged as the degree of exhaustion increased. The firstdischarge occurred in the form of bluish streamers when thepressure reached about 10 millimeters of mercury. At about5 millimeters the tube was completely filled by a pink glow.At about 2 millimeters the Faraday dark space appearednear the anode, and there was a bluish negative glow nearthe cathode. At successively lower pressure steps, striationsappeared in the vicinity of the anode stretching out towardthe cathode, and another dark space, now called theCrookes dark space, appeared surrounding the cathode. Thedark space was in turn surrounded by the blue negativeglow.

As the pressure was further reduced, the Crookes darkspace increased in size until finally it encompassed the en-tire tube. Crookes speculated that the dark space near thecathode was a region in which the cathode rays had a freepath before colliding with gas molecules. The blue negativeglow was caused by these collisions. This theory was laterconfirmed, and it was found that the cathode-ray particles,later called electrons, had enormous velocities of sometens of thousands of miles per second as they were shot outfrom the cathode.

Other inventions or discoveries by Sir William Crookesincluded the radiometer in 1875 and the spinthariscope inthe early 1900s. He also observed the fluorescence of var-ious minerals under the influence of ultraviolet light fromhis tube. Crookes was above a11 a chemist of considerablestature and was the discoverer of the element thallium.

LATER DEVELOPMENTS IN CATHODE RAYS

Jean Perrin of Paris in 1875 confirmed Varley’s hypothesisthat cathode rays were negatively charged particles. Hein-

230 Chapter Fifteen

rich Hertz and his assistant P. Lenard succeeded in passingcathode rays through an aluminum window at the end ofthe tube opposite the cathode and found that the rays werecapable of producing fluorescence outside the tube.J. J. Thomson in 1897 found the ratio of the charge e to

the mass m of the corpuscle, as he called the electron, andhe found also that after leaving the cathode these particlestravel at a speed of about one-fifth of the velocity of light,depending upon the applied voltage and the degree of ex-haustion of the tube. In 1906, Millikan, by means of his oildrop experiments, was able to determine the value of e as-1 .609 X 10-19 coulombs. When this value was substi-tuted in Thomson’s value for e/m Millikan found the massof the electron to be 9.1072 X lO-‘* gram.

The term electron was first suggested by Dr. G. JohnstoneStoney as a name for the natural unit of electricity in 1891.Later he applied the term to the cathode-ray particles thatJ. J. Thomson called corpuscles. It was not until the year1900, or a little later, that the name came into general use.

X RAYS

Among the many descendants of the Crookes tube was theX-ray tube. On November 8, 1895, Wilhelm Conrad R&it-gen, a professor of physics at Würzburg University, wasexperimenting with a Crookes tube when he discovered thata screen coated with a thin layer of barium platinocyanidelying nearby fluoresced when the tube was operating. Hefound that abjects placed between the tube and the screencast shadows upon the screen that were darker for abjectsof greater density . When the hand was interposed, thebones cast darker shadows than the flesh.

The source of the rays coming from the tube, which Ront-gen called X rays because their nature was unknown to him,

Crookes Tube, Structure of the Atom 231

Figure 15.3 Wilhelm C. Rontgen (From Smithsonian Institution)

232 Chapter Fifteen

was found to be the inside surface of the glass tube and theanode upon which the cathode rays impinged.

For several years after Rontgen’s discovery, there was adifference of opinion among scientists as to whether X rayswere particles or very short electromagnetic waves. It be-came clear after a time that they were probably electromag-netic waves, but the matter was not definitely settled untilabout 1912, when Max von Laue of Berlin with his associ-ates Friedrich and Knipping performed the crucial experi-ment in which X rays in a small beam were allowed to fa11upon a thin crystal where they were diffracted. The dif-fracted rays falling upon a photographie plate exhibitedsymmetrical patterns about a dark central spot.

Von Laue’s experiment led W. H. Bragg and his sonW. L. Bragg of London University to extend the experimentby using a crystal lattice to obtain an X-ray spectrogram.lnstead of sending the X rays through a small hole in a leadplate to obtain a fine beam, they used slits; and instead ofsending the X rays through a crystal, they reflected themfrom the face of a crystal. The crystal was mounted SO thatit could be rotated about an axis at the point at which theX rays were incident upon the crystal face. A strip of pho-tographic film was arranged in an arc of a circle whosetenter was the axis upon which the crystal rotated. Thespectrogram obtained by this method was similar to thatmade by a spectroscope with ordinary light. The lines onthe spectrogram were due to X rays of different wave-lengths reinforced by reflections from deeper layers of thecrystal lattice. Since the thickness of the layers could bedetermined, it became possible to find the wavelengths ofthe X rays. Even more important was the fact that an ar-rangement of this kind made it possible to study the struc-ture of crystals.

Crookes Tube, Structure of the Atom 233

Many improvements were made in X-ray tubes, some ofwhich came soon after Rontgen’s discovery, but the mostimportant improvement was made by William D. Coolidgeof the General Electric Company in 1913, when he substi-tuted a hot filament cathode for the cold cathode usedpreviously. The Coolidge X-ray tube provided many moreelectrons than the older tubes and was much more efficient.The source of electrons in the cold cathode tubes was prin-cipally the small amount of residual gas. Since the CoolidgeX-ray tube had no need of this gas it could be evacuated tothe highest degree possible.

X rays were used in the Vienna hospitals within a fewweeks after Rontgen’s discovery and were soon in use formedical purposes everywhere. Many other uses were foundsuch as metallography, crystallography, detection of hiddenabjects, and a very important use in the advancement ofresearch in atomic physics.

RADIOACTIVITYAfter the discovery of X rays, there was great interest in thepossibility that other still unknown kinds of radiationmight exist. Scientists were spurred on also by Hertz’s dis-covery of radio waves and by the particles known to existin a Crookes-tube stream. Henri Becquerel of Paris triedwrapping various minerals in black paper and placing themon photographie plates to determine whether or not therewas natural radiation from such minerals. He found thaturanium compounds did cause a blackening of the plates.On February 24,1896, he delivered a lecture on the subjectbefore the French Académie des Sciences in which he men-tioned the facts that, not only the compounds of uranium,but the metal itself caused the plates to darken and that

234 Chapter Fifteen

the radiation, whatever its nature, would discharge either apositively or negatively charged electroscope.

Within a short time G. C. Schmidt and Mme Marie Curiediscovered that thorium produced effects similar to ura-nium and that other elements showed slight radioactivity.

In Bohemia, at Joachimsthal, there was a mining operationin which pitchblende was extracted, from which uraniumwas recovered. Mme Curie had found that the residue,after the extraction of uranium, was radioactive and ar-ranged with the Austrian government to obtain about a tonof the material. She and her husband Pierre set to work ona long chemical process of refining and re-refining the pitch-blende to produce an increasing concentration of the radio-active substance. In 1898 they discovered the element polo-nium (atomic weight 210) and five months later discoveredradium (atomic weight 226). Polonium, named after MmeCurie’s native country, is highly radioactive but has a half-life of only 140 days. Radium, on the other hand, has ahalf-life of 1600 y ears. Various other radioactive substanceswere found within a short time including radon and actin-ium. Radon was an emanation from radium but was foundto be an element with an atomic weight of 222. The radia-tion from radioactive elements was found to be of threekinds, called alpha, beta, and gamma rays. Becquerel foundthat beta rays were negatively charged particles moving athigh velocity. Ernest Rutherford identified the alpha rays in1899 as slower-moving, positively charged particles. Thegamma rays, as was the case with X rays, were not deflectedby a magnetic field, and their nature was still a mystery.Gamma rays were far more penetrating than X rays andcould be detected after passing through 30 inches of iron.There was growing suspicion that they were electromag-netic waves, but Bragg believed that they were neutral

Crookes Tube, Structure of the Atom 2 3 5

particles. Only after von Laue in 1912 proved the electro-magnetic nature of X rays did it become apparent thatgamma rays were also electromagnetic.

SCATTERING OF ELECTRONS

About the year 1903, Lenard had used thin metal foils toallow electrons from a Crookes tube to escape to the out-side and had noticed a scattering of the rays as they emergedfrom the foil. The scattering was different for each of themetals used and the rays formed patterns that varied withthe kind of metal and the velocity of the particles. Hededuced from these experiments that most of the mass ofthe atom was concentrated in a small part of the totalvolume of the atom.

In 1911 Ernest Rutherford, who was at that time profes-sor of physics at Manchester University, announced theresults of a long series of experiments on the scattering ofalpha rays, later identified as helium nuclei, after passingthrough metal foils. Rutherford’s associates during theseexperiments, who carried out most of the work, wereH. Geiger and E. Marsden. The source of the alpha rays wasa bit of radioactive radon enclosed in a block of lead withonly a small aperture on one side through which the rayscould emerge as a narrow beam. A piece of metal foi1 wasplaced in the path of the rays, and behind the foi1 was asmall microscope mounted on an arm whose axis was thetenter line of the foil. At the end of the microscope was afluorescent screen that showed scintillations when struckby the alpha particles.

The experimenters counted the number of scintillationsper unit of time at various angles from the line of the beam,deriving a pattern in which the dots representing observedscintillations were more or less symmetrically placed

236 Chapter Fifteen

Figure 15.4 Ernest Rutherford (From Smithsonian Institution)

Crookes Tube, Structure of the Atom 237

around the tenter, Most of tbe rays were not deflected ata11 or very slightly. Rutherford assumed that the widelydeflected rays had collided with one or more atoms.

By means of very complicated reasoning and calculationsRutherford concluded that an atom is largely empty spaceand that most of its mass is confined to the positivelycharged tenter, later called the nucleus, which he calculatedhad a radius of less than 10-l* centimeter. He concludedthat the positive charge on the tenter was exactly equal tothe sum of the negative charges on the associated electrons.

PHOTOELECTRIC EFFECT

The term photoelectric effect is somewhat ambiguous.Usually the expression means the photoemission effect, inwhich electrons are freed from metallic surfaces by theaction of light. There are, however, two other photoelectriceffects, called the photovoltaic effect and the photoco.nduc-tive effect.

The photovoltaic effect was discovered in 1839 by Alex-andre E. Becquerel, fatber of Antoine Henri Becquerel. Hehad immersed two electrodes of the same material in anelectrolyte and found that when light shone upon one ofthem there was a difference of potential between them ofabout 0.1 volt.

In 1878 R. E. Day found that selenium exhibited a photo-voltaic effect. The photovoltaic properties of cuprous oxidewere discovered in 1930 by B. Lange, L. 0. Grondahl, andW. Schottky. Photovoltaic light meters using silicon wereintroduced in 1954 by D. M. Chapin, G. S. Fuller, and G. L.Pearson, following a suggestion by Paul Rappaport.

Willoughby Smith was the first to observe photoconduc-tivity in 1873; he found that small rods of seleniumbecame better conductors of electricity when they were

238 Chapter Fifteen

exposed to light. Other materials, such as cadmium sul-fide, were found to have similar properties by B. Guddenand R. Pohl in the 1920s.

Heinrich Hertz of Karlsruhe, Germany, observed in 1887that ultraviolet light falling on the electrodes of a spark gapwould cause the spark to jump a greater distance. Hallwachsfound, in the following year, that ultraviolet light falling ona negatively charged body would cause that body to lose itscharge very rapidly, whereas a positively charged body wasnot affected. Ten years later J. J. Thomson and P. Lenard,one of Hertz’s students, discovered independently thatlight falling on a metal surface would cause the emission ofnegatively charged particles, later identified as electrons andcalled photoelectrons.

For most metals only ultraviolet light Will cause photo-emission. The exceptions are the alkali metals such as so-dium, potassium, lithium, cesium, and rubidium.

PLANCK% CONSTANT

The same period that produced the important findings ofcathode rays, radioactivity, and photoemission also broughtforth a new concept relating to the energies of electrons orphotoelectrons. Max Planck of Berlin had been studyingblackb do y radiation during the year 1900, and in thecourse of these studies he derived a theoretical formula thatfitted his graphs of experimental results, giving the distribu-tion of radiated energy over a11 wavelengths for differenttemperatures.

In the derivation of this equation he found it necessary toassume that radiant ehergy was emitted in very small dis-crete bundles called quanta and that the magnitude of aquantum of energy was hv, in which v was the frequency ofthe radiation and h was a new universal constant that he

Crookes Tube, Structure of the Atom 2 3 9

called the quantum of action. The value of this newconstant was determined by Robert A. Millikan to be6.62 X 10mz7 erg second.

PHOTOELECTRONS AND EINSTEIN’S EQUATION

During the period from 1897 to 1905, a number of experi-menters made measurements of the velocities of cathoderays, Lenard rays, photoelectrons, beta rays, and rays fromheated metals. Foremost among these experimenters wasJ. J. Thomson. Ethers were Lenard, Becquerel, Seitz, Stark,and Reiger. In carrying out these experiments, various indi-rect methods were used including magnetic deflection, elec-trostatic deflection, heating effects, and acceleration orretardation in electric fields.

Albert Einstein, whose fame rests chiefly on his theory ofrelativity and his hypothesis regarding the mutual convert-ibility of rnatter and energy, made an important contribu-tion to the theory of photoelectrons in the year 1905. Hisproposition in this regard is expressed by the equation E =hv = W + ‘/mu’ . In this equation the energy E equals theproduct of the Planck constant h and the frequency of thephoton v (the Greek letter nu), which equals the sum of W,the work required to free the electron from the metal, andits kinetic energy %mv2. Here m is the mass of the electron,and u is its speed after being freed by the photon. The valueof v is determined by one or more of the rnethods men-tioned in the previous paragraph.

The work W is a variable depending on the kind of metalused. It is least for the alkali metals and greatest for theheavier metals, as might be expected, because of the greaterforce holding the electrons in the heavier metals. The veloc-ity of the photoelectron increases with the energy of thephoton. High-frequency photons have greater energies than

240 Chapter Fifteen

low-frequency photons, and in order to free electrons fromthe heavier metals ultraviolet light is required. Adding tothe intensity of the light does not change the velocity ofthe photoelectrons but increases their number.

HYDROGEN SPECTRAIn 1885 J. J. Balmer studied the visible spectrum of hydro-gen and derived the formula h = 3645.6 [rz’/(n’ - 4)] inwhich h (the Greek letter lambda) is the wavelength of abright line in angstrom units (one angstrom = 10-* centi-meter), and n is a whole number 3, 4, 5, . . . . It was shownthat the empirical formula also applied with considerableaccuracy to lines in the ultraviolet region. These lines of thehydrogen spectrum have since become known as the Balmerseries. Rydberg modified the formula by expressing it interms of frequency rather than wavelength giving the fol-lowing expression: l/h = 1 0 9 , 6 7 8 ](I/L’) - (l/n*)] i nwhich l09,678=R, the Rydberg constant.

STRUCTURE OF THE ATOMJohn Joseph Thomson (1856-1940), head of the Caven-dish Laboratory at Cambridge University (not to be con-fused with William Thomson, Lord Kelvin), mentor ofErnest Rutherford, had conceived of the atom as a posi-tively charged mass in which the electrons were embedded.This concept is sometimes referred to as the plum-puddingmodel. Such a mode1 failed to explain many of the knownfacts SO that Rutherford was forced, rather reluctantly, tothe conclusion that the negatively charged electrons couldbe kept away from the positively charged tenter only bycentrifugal force. This concept, however, led to anotherproblem that was not resolved until some years later;

Crookes Tube, Structure of the Atom 241

namely, a revolving electron, according to Maxwell’s equa-tions, should radiate energy.

At this Point Niels Bohr (1885- 1962), a native of Copen-hagen, studied for one year at Cambridge under J. J.Thomson and the following year (1912) at Manchesterunder Rutherford. He returned to Copenhagen in 1913,where he completed and published his epochal theory con-cerning the structure of the hydrogen atom. Bohr’s mode1of the hydrogen atom was based on Rutherford’s proposa1that the electron revolves about a positively charged nu-cleus. He assumed that in any atom there were as manyorbiting electrons as there were positive charges on the nu-cleus, and in order to overcome Rutherford’s objection, hepostulated that as long as an electron remains in a givenorbit there is no radiation of energy. He theorized furtherthat an electron may jump from one orbit to another. If itmoves to the next higher orbit, one quantum of energy isabsorbed, and if it jumps to the next lower orbit, one quan-tum of energy is radiated.

Bohr showed that in the hydrogen atom, which had onlyone positive charge and one electron, the electron had fiveor more possible orbits in which the forces within the atomwere in momentary equilibrium. The radii of these orbitswere related to one another in the ratio of their squares oras 1, 4, 9, 16, and 25. Normally the electron in the hydro-gen atom is in the lowest orbit, or ground state. When it isin a higher orbit, the atom is said to be excited. If sufficientenergy is supplied to the atom from the outside, electronsare not only sent into higher orbits but may be freed fromtheir atoms altogether as is the case in photoemission.

By inserting the value of h in his equations Bohr deter-mined that the innermost orbit of the hydrogen electronhad a radius of 0.5 X lO-’ centimeter and the higher orbits

2 4 2 Chapter Fifteen

had dimensions in proportion to the squares of their orbitnumbers. Furthermore Bohr was able to determine mathe-matically the wavelengths of the emission liAes in thehydrogen spectrum. His calculations agreed with theexperimental results obtained by Balmer, and in additionBohr calculated the wavelengths of the Lyman series ofspectral lines in the ultraviolet and the Paschen series in theinfrared, both of which had been determined experimen-tally in 1908. The Brackett and Pfund series in the infraredwere found later. In a11 cases Bohr’s calculations agreedwith the experimental results and established the truth ofthe Bohr theory almost beyond doubt.

HEAVIER ATOMS, ELLIPTICAL ORBITS, AND SPINFor atoms more complex than hydrogen, theoretical solu-tions for spectral lines are a11 but impossible, because of theinteractions of the orbiting electrons and such further com-plications as elliptical orbits and spin. In the heavier atomsthe radii of the orbits are smaller because of the greaterpositive charge on the nucleus. Despite these difficultiesthere could be little doubt as to the validity of the Bohrtheory and its applicability when it was extended to includethe heavier atoms.

Close examination of the spectral lines of hydrogen andother elements, particularly those of the alkali metals, re-vealed that many of the lines were multiples, SO close to-gether that it was difficult to separate them. Sommerfeldadvanced the theory that in some instances these multiplelines were due to elliptical orbits of the electrons. In 1925Goudsmit and Uhlenbeck proposed the idea that some ofthe lines, which were doublets, could be accounted for byassuming that some of the electrons were spinning abouttheir axes.

Crookes Tube, Structure of the Atom 243

THEORETICALANDEXPERIMENTALPHYSICSOFTHE1920s

The period of the 1920s was one of tremendous progress inthe development of atomic physics and quantum mechan-ics. In 1921 A. H. Compton discovered what is called theCompton effect. He found that when X rays were allowedto strike a carbon block other X rays of lower frequencyappeared. These new X rays had different frequencies indifferent directions. Their lower frequency resulted fromthe loss of energy caused by each collision between anX ray, which behaved much like a particle, and an electronof a carbon atom.

Louis de Broglie of France in 1922, advanced the theorythat atomic particles have wave properties. C. J. Davissonand L. H. Germer expanded de Broglie’s theory in 1927.

The year 1925 was filled with announcements of newtheories in the field of atomic physics and quantum me-chanics. W. Pauli set forth a rule in that year called thePauli exclusion principle which stated that in any atom not w o electrons may h a v e the same quantum numbers.E. Schrodinger of Germany developed the theory that anorbiting electron is a wave packet made up of standingwaves pulsing within the atom. The Schrodinger picture ofthe atom was extended by W. Heisenberg in 1925, by Bornin 1926, and by P. A. Dirac in 1928. The theories devel-oped by this group were expressed in mathematical termsand were found to be consistent with the Bohr theory.More than forty years have passed since these theories wereannounced, and they are still generally accepted as valid.

Bohr’s original concept of the atom was rather simple, butwith the passage of time the picture has become more andmore complicated. In 1912, about a year before the publi-cation of Bohr’s theory, H. G. Moseley, a Young Oxford

244 Chapter Fifteen

graduate, using the X-ray spectrograph, found a relationshipbetween the X-ray spectra of various elements and theiratomic weights. On the basis of this discovery he deducedthat the electrical charges on the nuclei of atoms were ofthe same order as their atomic weights. It had long beensuspected that most of the mass of an atom was concen-trated in its nucleus. No longer was the nucleus of the atomthought to be made up entirely of positively charged pro-tons, but it was believed to contain neutrons as well. Thisnew concept of the atom was soon to become very impor-tant.

OTHER SUBATOMIC PARTICLES

Theories as to the nature of matter were changing rapidly,especially after the finding of new particles. In 1932J. Chadwick of England discovered the neutron, and in thesame year C. D. Anderson discovered the positron. The neu-tron was described as a particle similar to the proton butwithout a charge. Chadwick’s discovery was aided by earlierresearch by Bothe and Becker of Germany and Irène Curieand her husband, Frédéric Joliot. The positron was a verysmall particle, similar to the electron but with a positivecharge. Soon after the discovery of the positron, J. R.Oppenheimer succeeded in producing an electron pair, posi-tive and negative electrons, by the use of powerful gammarays. A great number of other subatomic particles havebeen postulated to explain various phenomena, some ofwhich perhaps exist and others of which may be differentmanifestations of more familiar particles.

Awareness of the existence of cosmic rays started aroundthe beginning of the Century. Their source is in outer space,but their exact origin is unknown. They consist of protons,alpha particles, and a smaller number of the nuclei of heav-

Crookes Tube, Structure of the Atom 243

ier atoms. They have exceedingly high energies much ofwhich is lost as the rays travel through the atmosphere. Asthey collide with air molecules thousands of secondary cos-mit rays are produced. In the course of this bombardment,positive and negative electron pairs are produced that re-unite immediately and are annihilated. A very interestingparticle that is a product of cosmic ray collisions is the pimeson. The pi meson may be positively or negativelycharged or neutral. It has a mass 275 times that of an elec-tron, and it may achieve a velocity close to that of light.Charged pi mesons disintegrate in a small fraction of a sec-ond to form charged mu mesons and a particle called aneutrino. The mu meson, in turn, decays in another smallfraction of a second, producing an electron and two neu-trinos. The neutral mesons are very unstable and disinte-grate even more quickly than the charged mesons into twogamma rays.

Since this is a history of electricity and magnetism, itwould not be appropriate to pursue the subjects of atomicphysics and quantum mechanics in great detail. Althoughthese studies had their origins in electrical phenomena, theyhave now extended into regions only remotely connectedwith the purposes of this book. The remaining discussion ofthese matters Will therefore be brief and Will be in thenature of an outline.

THE ELECTRON MICROSCOPE

De Broglie’s and Schrodinger’s hypotheses of the early andmiddle 1920s indicated that electrons behave in some re-spects like particles and in other ways like waves. HansBusch of Germany showed in 1926 that an electron beamcould be focused by an electrostatic or magnetic field.Ernst Bruche and H. Johannson, also of Germany, in 1932

246 Chapter Fifteen

succeeded in producing an image of a heated cathode, usingelectrostatic lenses. Two years later, Max Knoll and ErnstRuska of Germany constructed the first electron micro-scope equipped with magnetic lenses. Siemens and Halskebuilt an electron microscope in 1935 based on a design byvon Borries and Ruska, which had a resolving power of100 angstroms.In North America, work on the electron microscope was

begun in 1935 at the University of California and at BellLaboratories. RCA Laboratories began its work in 1936under the direction of Dr. V. K. Zworykin. In the sameyear work was also started at the University of Toronto.

Electron microscopes may use either magnetic or electro-static lenses, but very few have been built with electrostaticlenses. Electron microscopes have been built commerciallyby Siemens and Halske and several other European manu-facturers. In the United States they have been produced byRCA and General Electric.

In an electron microscope the entire system is enclosed ina chamber that has been exhausted to a pressure of 10-’ at-mosphere. Since the specimen to be observed is also en-closed in the vacuum chamber, its moisture must be re-moved. Because of this, biological specimens are greatlyaltered, and the usefulness of the instrument is therebydiminished.

The electron microscope is one of the descendants of theCrookes tube. The source of the electrons in the micro-scope is a hot cathode that furnishes many more electronsthan the cold cathode of the Crookes tube. In order topropel the electrons toward the lower end of the tube, itis necessary to provide a potential difference of from10 to 100 kilovolts between the cathode and the target.The electron beam is brought to a focus at the specimen by

Crookes Tube, Structure of the Atom 247

means of a toroidal magnet that behaves somewhat like alens. The beam, after passing through the specimen, isbrought to a focus at the screen, which is a plate coatedwith a fluorescent material. A photographie film may besubstituted for the screen. An ordinary optical microscopeis capable of magnification up to 2000 diameters, while anelectron microscope may magnify up to 200,000 diameters,with a resolving power of about 10 angstroms.

RADIATION DETECTORSResearch in the field of radiation of both particles andelectromagnetic waves was largely dependent upon the in-vention of suitable devices for the detection of such radia-tion and the showing or measurement of its effects. There isnow a long list of such devices including the electroscope,the photographie film, the spinthariscope, the ionizationchamber, the Geiger-Müller counter, the cloud chamber, thefluorescent screen, the scintillator, the bubble chamber,radio wave detectors, the radiometer, the thermometer, andthe phototube. Al1 of these and others have played an im-portant role in the amazing list of discoveries which fol-lowed the invention of the Crookes tube and the discoveryof radio waves, the X ray, and radioactivity.Radio wave detectors were mentioned in an earlier chap-

ter, and others such as the electroscope, the radiometer andthe thermometer have been used for many years. One ofthe most useful detectors for radioactivity has been thecloud chamber, invented by C. T. R. Wilson of CambridgeUniversity in 1912 or perhaps somewhat earlier. In thecloud chamber, the tracks of moving charged particles be-come visible as they cause the formation of tiny droplets ofwater in a cloud of water vapor in a glass vessel. A cloud isformed in the vesse1 above the water in the bottom when

248 Chapter Fifteen

the pressure is suddenly decreased by means of a bulb at-tached to the vessel.

An ionization chamber is a small box or glass tube intowhich electrified particles are introduced, causing the en-closed gas to become ionized. When a battery and galva-nometer are connected between the two electrodes, a weakcurrent Will flow through the ionized gas. This current Willbe proportional to the amount of ionization and the bat-tery voltage and Will indicate the amount of ionization.

The Geiger counter was originally invented by Hans Geigerbetween 1908 and 1913 and later was much improved byGeiger and H. Müller. The Geiger-Müller counter consists ofa partially evacuated glass tube containing a short coppertube through the tenter of which a wire is stretched. Thepositive terminal of a high-voltage battery is connected tothe copper tube, and the circuit is completed through agalvanometer and the central wire. In more modern instru-ments, the galvanometer is replaced by an amplifier andtelephone receiver in which every ray that reaches the coun-ter is registered by a click.

The bubble chamber is a much later modification of thecloud chamber, in which a liquid heated to near its boilingpoint is used in place of saturated water vapor. An electri-fied particle passing through the liquid leaves a trail of bub-bles.

One of the better and more recent detectors is the scintil-lation counter; it is a combination of a screen that Will emitflashes of light when struck by alpha, beta, or gamma raysor by a11 three and a photomultiplier tube. The screen isplaced in close proximity to the cathode of a photomulti-plier tube that is highly sensitive to light, especially in theblue or violet region. A tiny flash on the screen Will liberateone or more electrons from the cathode, depending on the

Crookes Tube, Structure of the Atom 249

intensity of the flash. Below the cathode is a series ofscreens arranged in zigzag fashion, positively charged, andcoated with a material that Will give up electrons freelywhen struck by other electrons. As its name indicates, thephotomultiplier tube produces many more electrons thanthe original number, SO that the collecter at the bottom ofthe tube receives an avalanche of electrons. A scintillationcounter is a very sensitive detector that is also very fast,with a resolving time ranging from 10-’ to 10s9 seconds.

ACCELERATORS AND ATOMIC RESEARCHPrior to 1932, the only method available for the disruptionof atoms was bombardment with alpha rays from radio-active materials. Physicists generally were convinced thatfar better results could be obtained by accelerating atomicparticles by artificial means. The energy of alpha rays fromradioactive substances was limited, and the particles wereprojected in random directions, SO that they could not beconcentrated on a desired target.

Rutherford, who had observed nuclear disruption with theuse of alpha rays in 1919, laid plans in 1930 for the con-struction of a million-volt generator, to be built at the Cav-endish Laboratory for use with an accelerator. Two ofRutherford’s assistants, Cockroft and Walton, became im-patient and in 1932 completed a smaller accelerator, using150,000 volts. With it they succeeded in projecting protonsfrom hydrogen at a velocity sufficient to disrupt the nu-cleus of a lithium atom, an event which was accompaniedby the release of energy.

Similar activities were under way at other universities. AtPrinceton, R. .J. Van de Graaff in 1931 completed a belt-type electrostatic generator that produced a potential of1.5 million volts. Van de Graaff transferred to M.I.T. the

250 Chapter Fifteen

following year, where he collaborated with K. T. Comptonin the construction of a larger machine. They completed a5.1-MV generator in 1936 that was immediately put towork on nuclear research. In order to overcome corona andmoisture difficulties, more powerful generators were laterhoused in pressurized steel buildings. The highest voltageachieved in a Van de Graaff generator was 12 MV.

At the University of California, at the same time as theseother projects, work was in progress on a different type ofaccelerator, called the cyclotron. This project began in1930 under the direction of E. 0. Lawrence. The cyclotronconsisted of a flat, circular vacuum chamber inside of whichwere two hollow semicircular electrodes, called dees. Thevacuum chamber was mounted between the poles of apowerful electromagnet. Inside the chamber, near the cen-ter, was a source of hydrogen ions that were accelerated bythe high-frequency electrostatic field from the dees. Themagnetic field caused the ions to travel in a spiral of in-creasing radius at enormous velocities until they were fi-nally ejected through an aluminum window. The first cyclo-tron was completed in 1932 and yielded only 0.8-MeV ions,but a 60-inch machine, completed in 1939, produced40-MeV ions. The abbreviation MeV stands for millionelectron volts. One electron volt is the energy acquired byone electron when accelerated through a potential differenceof 1 volt.At the University of Illinois, D. W. Kerst conceived and

built an accelerator called the betatron because it produceda powerful beam of electrons, or beta rays, whereas thecyclotron yielded a beam comparable to alpha rays. Severalprevious attempts had been made to construct an electronaccelerator, the earliest of which was made by J. Slepian in1922, followed by Breit and Tuve in 1927, and Wideroe in

Croohes Tube, Structure of the Atom 251

1928. Still other attempts were made by Walton, Jasinsky,and Steenbeck. The Illinois betatron was compl&ed in

1940 and produced 2.3-MeV electrons.The betatron consists of a doughnut-shaped vacuum cham-

ber made of glass or porcelain, containing an electron gun,a11 of which is mounted between the poles of a strong alter-nating magnet operating at 60 to 180 cycles per second.Short bursts from the electron gun are timed to correspondwith the proper phase of the magnetic cycle. Al1 of theelectrons travel in a single path at the tenter of the tube,and herein lay the difficulty experienced by the earlierexperimenters, who were unable to keep the electronstream stable. The electrons may spin around through thetube as many as 200,000 times in a quarter cycle of themagnetic field and travel at velocities approaching that oflight. Not only is the betatron a source of high-speed elec-trons, it is also used to produce hard and very penetrating Xrays. The largest betatron was built by the General ElectricCompany about the year 1946. It had a magnet weighing400 tons and produced electrons with energies of 340 MeV.

Another accelerator called the synchrotron is a cross be-tween a cyclotron and a betatron. It has a doughnut-shapedevacuated tube like the betatron, but inside the tube, inaddition to the electron gun, are tubular electrodes corres-ponding to the dees of the cyclotron. Acceleration of theelectron is begun on the betatron principle using the alter-nating electromagnet after which further acceleration isproduced by the electrostatic field from the electrodes onthe cyclotron principle. Some of these machines acceleratedelectrons to 99.99 percent of the speed of light with anincrease in mass of 600 times the rest mass.

A modification of the synchrotron, built at the CERNlaboratory in Geneva in 1959, was used for accelerating pro-

232 Chapter Fifteen

tons and was capable of energies up to 28 BeV (billion elec-tron volts). Another such machine, called the cosmotron,was put into service at the Brookhaven National Laboratoryin 1960 and was capable of producing 33 BeV.

The fifth important type of accelerator is called the linearaccelerator because, as the name implies, the acceleratedparticles move in a straight line. Ising of Sweden proposedsuch a device in 1925 but did not actually build one.E. Wideroe, of Brown Boveri in Switzerland, built a smalllinear accelerator with three electrodes in 1928. It was fol-lowed a short time later by a machine with ten electrodesbuilt by D. H. SIoan of the University of California. Otherswho worked on the problem were J. W. Beams of the Uni-versity of Virginia, who built a linear accelerator yielding1.3 MeV. W. W. Hansen of Stanford University began hiswork on linear accelerators in 1930 and as a by-productinvented the rumbatron, from which Russell and SigurdVarian developed the klystron oscillator tube in 1937.After World War II, L. Alvarez and W. K. H. Panofsky ofthe University of California attacked the problem, andwork was also resumed at Stanford University. On Septem-ber 9, 1967, a lO,OOO-foot linear accelerator became opera-tional at Stanford University. It was built by the universityunder the sponsorship of the U. S. Atomic Energy Com-mission.

16

Microwaves, RadarRadio Relay,

Coaxial Cable, Computers

MICROWAVES

Microwaves are radio waves with wavelengths lying in theelectromagnetic wave spec t rum be tween 1 meter andl/ie centimeter. They have properties quite unlike the radiowaves used for broadcasting. These short waves are muchmore directional, are propagated in straight lines like light,and cari be confined within a tube or waveguide. Because oftheir very short wavelengths, microwaves require specialequipment for their generation and reception. Ordinaryradio circuits have components of capacity and inductancethat render them entirely unfit for microwaves.

Microwaves have been put to various uses, the most im-portant of which are radar and radio relay telephone cir-cuits.

RADAR

Radar was very largely a development resulting from de-fense requirements in World War II, although early forms ofradar were in existence as early as 1934 and were in usealong the British east toast several years later.

The conception of radar was not the invention of anysingle individual or group but rather came into existence bysteps with contributions by many research scientists. Thepioneers in microwave development were Dr. Irving Wolffof RCA and 1. E. Mouromtseff of the Westinghouse Com-pany in the early 1930s.

An essential part of pulse radar, the most common form,was the cathode-ray tube, whose ancestor was the Crookes

254 Chapter Sixteen

tube. As was mentioned previously in connection with tele-vision, the cathode-ray tube was the invention of Karl F.Braun, who applied it to his oscilloscope in 1897, and itwas this tube that became the receiving screen of radar andof television.

The word radar was coined by S. M. Tucker of the UnitedStates Navy from the name Radio Detection and Ra+ng.Radar is essentially a method of detecting the presence of,and the direction and distance of, abjects not ordinarilyvisible because of darkness, fog, or distance. It also has thecapability, in another form, of determining the speed ofmoving abjects and the direction in which they are moving.These results are accomplished by reflecting microwavesfrom the abjects under observation and receiving the re-flected signal by suitable means. In wartime use, radarserved not only to detect enemy ships and planes but wasused also to direct gunfire with incredible accuracy.

The first discovery leading to the development of radarwas made in 1922 by engineers of the U. S. Naval ResearchLaboratory when they observed that radio waves were re-flected back to the transmitter by a ship passing between asending and receiving station. Beginning with that observa-tion and continuing until 1930, the laboratory performedmany experiments on the same phenomenon and con-structed primitive forms of radar using ordinary radiowaves.

EARLY BRITISH DEVELOPMENTSAND INSTALLATIONS

During the 1930s when Britain was already aware that itmight be vulnerable to attack from the continent, earlyforms of radar were installed along the eastern and southerntoasts of the island. In 1936 there were five such stations;

Microwaves, Coaxial Ca})le, Computers 25.5

in 1937 there were twenty, and more were added in 1938and 1939. These installations used a wavelength of 1.5 me-ters, the shortest length which was possible by the then-existing equipment. The person chietly responsible for thiswork was Robert Alexander Watson-Watt. The Britishrealized that to be most effective radar required muchshorter wavelengths, especially for airborne radar. The prob-lem was submitted to a research team at the University ofBirmingham, which about the year 1940 produced an earlyform of the magnetron oscillator.

AMERICAN WARTIME RESEARCH

AND DEVELOPMENT

When the war began in 1939, various of the research labora-tories of American companies took up the radar problem inearnest. Among those working on this problem were RCA,General Electric, Westinghouse, Bell Laboratories, WesternElectric, Philco, Raytheon, Hazeltine, Sperry, Federal Tele-phone, Bendix, and others.

In 1940 the Radiation Laboratory was established atM.I.T., which had on its roster most of the men in theUnited States who had knowledge of microwaves. This or-ganization worked closely with its British counterparts andwith the various radio manufacturers to develop and pro-duce as quickly as possible the most effective radar equip-ment within their capabilities. The British contributedtheir version of the magnetron tube, which was improvedupon and was soon produced in quantity by the GeneralElectric Company. Between the work of the RadiationLaboratory and the research organizations of the manu-facturing companies, progress was little short of miraculous,SO that what might have taken years to develop was donein months. The elapsed time between laboratory experi-

256 Chapter Sixteen

ment and operation on the war front was sometimes amatter of weeks.

NEW OSCILLATORS AND OTHER TUBESRadar made necessary the production of hundreds of newtypes of vacuum tubes unlike anything previously manu-factured. The reason was, of course, that the inherentcapacitance and inductance of the older tubes renderedthem unfit for microwaves. Furthermore, the transit timeof electrons moving from cathode to plate in an ordinarytube was SO great that the grid voltage might be reversedbefore the electron had traversed more than a part of therequired distance, and the tube would become inoperative.The parts of the microwave tubes had to be made muchsmaller and closer together than in the standard tubes.

There was an even greater problem involved in the manu-facturing of oscillator tubes because these were required toput out rather large amounts of power and still have in-ternal characteristics suitable for microwave operation.Three general types of such tubes were made: the light-house tube, so-named because of its shape, for smallerpower output; the magnetron for large power output; andthe klystron, a versatile kind of tube with a wide frequencyrange, used for both transmitters and receivers.

The lighthouse tube cari operate up to 4000 megacycles,at relatively low power. The magnetron, which uses a strongpermanent magnet to cause the electrons issuing from thecathode to move in circular orbits within several chambers,is capable of producing waves with wavelengths of 1 centi-meter or less and cari reach peak outputs measured in mega-watts. The klystron like the magnetron has cavity reson-ators but is adjustable over a much wider range and is there-

Microwaves, Coaxial Gable, Computers 257

fore suitable as an oscillator tube for FM as well as micro-wave transmission and reception.

TYPES OF RADARIn the earliest radar sets the pulse system was used, and thissystem is still the most common. Signals from the trans-mitter are beamed toward the target in pulses only a fewmicroseconds in length, each of which is followed by apause of much greater duration. The pulse repetition fre-quency (PRF) may vary from 60 to 4000 per second. Thepulse repetition time (PRT) may therefore vary between16,667 and 250 microseconds (millionths of a second). Theduration of a single pulse is often only a fraction of 1 per-cent of the time between pulses, which means that the peakoutput of an oscillator tube may be several thousand timesits average power.

In most cases radar is used to scan the entire 360 degreesaround the transmitter, and for that reason a rotating orsweep antenna is used. The return signal is generally re-ceived by the same antenna, which in the meantime hasrotated through a small angle depending upon the distanceof the target. The received signal is heterodyned, amplified,and demodulated, after which the pulses are fed into acathode-ray tube where the target Will appear in whiteagainst a greenish background. The screen is provided withsuitable markings, to indicate distance and orientation.

Two other types of radar have been developed called FM,and frequency shift radar. In FM radar the frequencychanges constantly through a predetermined range, cor-responding to the pulse in pulse radar. The distance of thetarget is determined by the beat frequency between theincoming and outgoing signals, and may be read directly onsuitably calibrated instruments.

258 Chapter Sixteen

Frequency shift radar is of the pulse type, designed specif-ically to measure the speed of a moving target by utilizingthe Doppler effect. The reflected signal from the movingtarget is received by the same antenna as the outgoing sig-nal. The received signal is then compared with the constantfrequency of an oscillator other than the transmitter, andby means of suitably calibrated instruments the speed ofthe target cari be read directly. This is the type of radarused by highway police.

OTHER USES OF RADAR

The use of radar during World War II helped save Englandand contributed to the destruction of the enemy. Since thattime the military uses of radar have been greatly expandedand refined. Many peacetime applications have been intro-duced, such as marine navigation, airport landing devices,police radar, and weather forecasting.

TELEPHONE RADIO RELAYPerhaps the most important peacetime application ofmicrowaves was in the telephone industry for what is calledTelephone Radio Relay. Ordinary long radio waves hadbeen used for a number of years for voice communication,facsimile transmission, teletypewriter service, network tele-vision and radio, and telemetering.

Telephone Radio Relay was first introduced in the UnitedStates by the Bell System in 1947, using the 4000-mega-cycle band. In such a system microwaves are sent from aterminal, through a directional antenna, to a tower somemiles distant. Here the signal is amplified and may bechanged in frequency, after which it is sent on to a secondtower, and SO on, until it is received at the distant terminal.The relay towers are about 30 miles apart and are purposely

Microwaves, Coaxial Gable, Computers 259

set in zigzag fashion to prevent what is called overreach,which means the picking up of a signal by a more distanttower instead of the nearer one for which it was intended.

FREQUENCY BAND ALLOCATIONSIn 1949 the Federal Communications Commission allocatedthree frequency bands for telephone radio relay communi-cation: 4000, 6000, and 11,000 megacycles, each of whichwas 500 to 600 Mc in width. In the early experimental useof the 4000-Mc band there were six channels each of whichwas capable of providing 480 circuits. In 1959 the samefrequency band was divided into twelve channels, and morerecently each of these channels was made capable of provid-ing 900 circuits, making a total of 10,800 circuits in the4000-Mc band alone. In practice two of the channels arereserved for standby, leaving 9000 working circuits. Stillmore recent improvements, involving the use of transistors,Will increase the capacity of each channel to 1200 circuits.

When the 4000-Mc band began to approach the limit of itscapability, work was begun on the use of the 6000-Mcband, which was divided into eight channels, two of whichw e r e s t a n d b y . Each hc annel furnished 1800 circuits,making a total of 10,800 working circuits. Both the4000-Mc and 6000-Mc bands have been used principally for1 ong-distance service, between important terminals, butmore recently a portion of the 6000-Mc band has been usedfor what is called short-haul service.

The capabilities of the ll,OOO-Mc band have probably notbeen fully developed up to this time. This band is less ef-ficient than either the 4000- or 6000-Mc band for the rea-son that the very short waves have a shorter range and areweakened by the presence of raindrops in the atmosphere.The ll,OOO-Mc band has therefore been used primarily for

260 Chapter Sixteen

short-haul service, especially in dry areas. It cari supply600 circuits over distances of 200 miles in dry regions and100 miles elsewhere, but repeater stations are much closerthan with the longer wavelengths.

TO provide the large number of circuits per channel themicrowave is modulated by the signal and by a carrier wave,and in addition the outgoing signals are polarized horizon-tally and vertically. At the receiving end the signals arefiltered out and reappear as ordinary telephone messages inthe telephone exchange. The relay towers have two sets ofantennas, one for sending and one for receiving, and a two-way telephone conversation follows two different paths be-tween stations.

COAXIAL CABLE

Coaxial table was invented by two Bell System engineers inthe 1920s: Herman A. Affel and Lloyd Espenschied, whoapplied for a patent in 1929. The capabilities of such atable were demonstrated experimentally in 1936 by a linebetween New York and Philadelphia. In 1941 the first com-mercial coaxial table was laid between Minneapolis andStevens Point, Wisconsin, a distance of 195 miles. This in-stallation originally provided 480 two-way telephone cir-cuits. This table contained four coaxial tubes; two of whichwere for standby.A coaxial tube consists of a 3/s -inch copper pipe in the

tenter of which is a No. 10 copper wire. The wire is held inplace by perforated plastic disks spaced about 1 inch apart.At least two coaxial tables are required for a line: one foroutgoing and the other for return signals. At the presenttime tables containing up to twenty tubes are being manu-factured. The sheath for such a table is made up of layersof polyethylene and lead and is sometimes protected by an

Microwaves, Coaxial Gable, Computers 261

outer armor of steel tape. Inside the table and alongside thecoaxial tubes insulated wires are placed for use by main-tenance crews to enable them to communicate with stationsalong the route. Generally the tables are buried in trenches,but sometimes they are carried overhead for short dis-tances. The trench also contains ground wires placed oneither side of and above the table for lightning protection.

The original Minneapolis-Stevens Point line operated inthe 68- to 2788-kilocycle range with repeater stations7.8 miles apart. This line had a capacity of 480 voice cir-cuits, later increased to 600. In 1953 a table was completedbetween New York and Philadelphia operating in the 312-to 8224-kilocycle range that had a eapacity of 1860 voicecircuits for each pair. In this installation repeater stationswere 4 miles apart. A more recent development was a20-tube table, a test installation of which was made be-tween Dayton and Rudolph, Ohio, in 1965. A 20-tubetable was put into service between Washington and Miamiin 1967. It has a total capability of 32,400 circuits andoperates in the 564- to 17,548-kilocycle range, with re-peater stations 2 miles apart.

Experimental work is under way for the use of what iscalled pulse code modulation for use on coaxial tables,which is expected to increase the capability of these tablesstill further and Will eliminate distortion.

There are at the present time about 15,000 miles ofcoaxial tables in the United States. Although radio relayhandles almost a11 intercity television program transmissionand about two-thirds of other long-distance communica-tion, coaxial table is growing more rapidly and presumablyWill in the future account for a larger proportion of tele-phone traffic. With the introduction of larger coaxial tablesthe cost per circuit has been decreasing until it is now about

262 Chapter Sixteen

Figure 16.1 Coax-20 Coaxial Cable. This table, approximatelythree inches in diameter, handles 32,400 voice channels simultane-ously. (Courtesy Bell Labs)

the same as radio relay. In general coaxial table is some-what more reliable than radio relay but is subject to damagebecause of being accidentally dug up or plowed up.The Bell System is also conducting research on the use of

laser beams for communication.

COMPUTERSIt is difficult to trace the ancestry of modern electroniccomputers except to say that they were preceded by vari-ous kinds of mechanical calculating devices going back tothe abacus, which is still widely used in many countries in

Microwaves, Coaxial Gable, Computers 263

the Orient. The earliest form of desk calculator was intro-duced by Pascal in 1642 and was used only for addition. Amodification of the Pascal machine was made by Leibniz in1671, and this machine was capable of performing multipli-cation. Charles Xavier Thomas of Colmar in 1820 was thefirst to make calculating machines commercially. TheThomas machine was not altogether reliable and thereforewas not a success. The Brunsviga calculator, invented byBohdner in 1876, was produced commercially several yearslater and was very successful. This machine, manufacturedin Germany, could add, subtract, multiply, and divide andwas the prototype of the many desk calculators of lateryears.

The slide rule had its beginning with Gunter’s logarithmicscale in 1620. The sliding scale was introduced by Wingateof England in 1672. Lieutenant Amédée Mannheim ofthe French army introduced the modern form of slide rulein 1850.

Probably the earliest integrator device was Amsler’splanimeter, which dates back to about the year 1854. It hadbeen preceded by somewhat similar contrivances made byConradi and Fleischauer.

Computer development was aided by the invention of tab-ulating machines, using punched cards. The first such ma-chine was invented by Dr. Herman Hollerith of the UnitedStates Census Bureau in the middle 1880s. The 1880 censusreports were delayed several years because of the vastamount of clerical work involved. Dr. Hollerith foresaw thepossibility that future reports, because of their increasingcomplexity, could not be completed before the beginningof the next census.

He conceived the idea of using punched çards to expeditetabulating the information gathered in the census. The idea

264 Chapter Sixteen

was borrowed from the Jacquard loom, in which longsheets of punched cardboard were used to instruct the loomin the weaving of intricate patterns. Even the use ofpunched cards for statistical purposes was not new, becauseCharles Babbage, of England, had made such a suggestion asearly as 1840 but had not carried out the idea.

Hollerith began work on the punched tard system in themiddle 1880s and within a few years had produced theequipment that was used successfully in tabulating the1890 census returns. Business concerns began to adopt thesystem, and to meet their demands Dr. Hollerith formed acompany in the 1880s called EAM for Electric AccountingMachines. The company was reorganized in 1911 as theComputing Tabulating Recording Company, and in 1924 itbecame International Business Machines, or IBM.

Another company that played an important part in com-puter development was Remington-Rand Inc., which wasformed by the merger in 1927 of the Remington Type-writer Company and the Rand Kardex Corporation. Rem-ington-Rand Inc. acquired the Eckert-Mauchly ComputerCorporation in 1949. In 1955 Remington-Rand and theSperry Corporation merged to form the Sperry-Rand Corpo-ration. Among the many products of the new company areUNIVAC computers, punched tard systems, tape, and othercomputer supplies.

Beginning in the early 1950s many other American firmsentered the computer field, including General Electric, Con-trol Data Corporation, Honeywell, Digital Equipment Cor-poration, National Cash Register, Philco, RCA, Raytheon,and Burroughs. In addition, there are hundreds of elec-tronic companies producing magnetic tape, disks, drums,cores, paper tape, cards, transistors, and the many otheritems which are used in connection with computers. In ad-

Microwaves, Coaxial Gable, Computers 265

dition to the American companies, there are now manycompanies abroad that are in the computer business.

COMPUTER DEVELOPMENTCharles Babbage, who was born at Totnes in Devonshire, onDecember 26, 1792, was the son of a banker. He enteredCambridge University in 1810, where he became an out-standing student of mathematics. He was distressed by thefact that many of the mathematical tables of the time werefull of errors. In 1812, with an open book of logarithmtables before him, he conceived the idea of building a com-puting machine that could be used to produce such tablesand that would be free of human errer. For some years hespent much of his time in an effort to des@ such a ma-chine. As a result of his labors he produced a machine in1822, which he called a Difference Engine, S O namedbecause it was designed to calculate such quantities as loga-rithms and trigonometric functions for use in tables,based upon differences. This machine was capable of calcu-lating the values of simple equations to six decimal places.Babbage’s next effort was to build a larger Difference En-gine capable of making calculations of such quantities up totwenty decimal places, but he found that machine shoptools and technology of the time were not sufficiently ad-vanced to build a machine of this degree of complexity. In1833 Babbage designed a different type of machine, whichhe called his Analytical Engine. This machine, to whichBabbage devoted the remainder of his life but which henever succeeded in building, was a mechanical computer. Ithad four basic parts comparable with those of a moderncomputer. One of these he called the store, which was alimited mechanical memory. Another part he designated asthe mil1 in which the calculations were carried out. A third

266 Chapter Sixteen

part was designed to transfer information between thestore and the mill, and the fourth part was the outputportion of the machine. Babbage’s design called for havingthe machine print the results.In 1876 Lord Kelvin described an analog type of com-

puter that was designed to solve differential equations, butthis too was never built. The first computer to be com-pleted and put to use, excluding Babbage’s Difference En-gine, was built by Dr. Vannevar Bush and his associates atthe Massachusetts Institute of Technology. This machine,begun in the middle 192Os, was completed in 1930. It wasentirely mechanical, cumbersome, and slow, but it wascapable of solving complex problems. Its greatest fault wasthat the time required to set up the machine, or in moremodern terms, to program it, was very long. Copies of thismachine were built in the 1930s: one for the AberdeenProving Ground and another for the Moore School of Elec-trical Engineering at the University of Pennsylvania.

During the 1930s Dr. George R. Stibitz of Bell TelephoneLaboratories designed and built a computer for use in thecalculation of alternating-current problems involving theuse of complex numbers. This machine used telephone re-lays instead of gears, cams, and levers employed by theearlier computers. Input to the machine was by means of akeyboard, and the output was delivered by a teletypewriter.

Dr. Vannevar Bush and his co-workers completed a greatlyimproved computer in 1942 in which many of the opera-tions were carried out by means of electrical relays andswitches but which still contained mostly mechanicalcounting devices.

Dr. Howard Aiken, professor of mathematics at HarvardUniversity, began the construction of a computer in 1937,with the assistance of J. W. Bryce, C. D. Lake, B. M.

Microwaves, Coaxial Cahle, Computers 267

Durfee, and F. E. Hamilton of IBM. The project was fi-nanced by the U. S. Navy. This machine, called the Auto-matic Sequence Controlled Calculator, or Mark 1, was com-pleted in 1944. It contained electrical relays and switchesbut was still mostly mechanical. Input and control of themachine were accomplished by the use of punched papertape, and the output was recorded by means of automatictypewriters. The Mark 1 computer operated successfullyover a period of about fifteen years before it was retired,but compared with later machines it was slow. The calcula-tion of a logarithm, for example, required 90 seconds.

A second computer, called Mark II, was begun by thisgroup in 1945 and completed in 1947. It contained some13,000 electrical relays and could store 100 numbers of10 digits each in addition to a sign for each number. Inputto the machine was by means of punched paper tape, andpaper tape was also used as supplemental intermediatestorage. Output from Mark II was recorded by automaticprinters or typewriters. Its speed was much greater thanthat of Mark 1, but it was still very slow in comparison withlater machines.

DIGITAL AND ANALOG COMPUTERS

Computers are of two general types, digital and analog, butthe distinction is now rapidly disappearing. A digital com-puter, as the name implies, operates upon discrete numbersand performs arithmetic computations. An analog com-puter is capable of calculating transcendental functions orof solving differential equations. As its name indicates, ananalog computer uses analogs such as voltages, resistances,angles, revolutions, lengths, or other measureable quantitiesto represent the actual amounts. A digital computer is

268 Chapter Sixteen

exact, but an analog computer, because of the nature of thequantities involved and the kinds of measurements made,cannot be absolutely accurate.

ELECTRONIC COMPUTERS

The first electronic computer, called Mark III, or ENIAC forElectronic Numerical Integrator and Calculator, was builtfor the U. S. Army under the direction of Drs. J. P. Eckertand John Mauchly of the Moore School of Electrical En-gineering. This machine, begun in 1942, was completed in1945. It contained 18,000 vacuum tubes and 6000 switchesand required about 150 kilowatts of electrical power for itsoperation. ENIAC was the first computer to use the binarysystem for a11 of its operations except the storage section.The storage or memory section consisted of energizedvacuum tubes and was capable of storing 200 ten digit num-bers.

Following the ENIAC the next important developmentwas the IBM Selective Sequence Electronic Calculatorcompleted in 1948. This machine also used vacuum tubesand relays and operated on the binary system.

In England, where the earliest computer ideas originatedwith Babbage and Lord Kelvin, work on computers wasgoing on also but at a somewhat slower pace. The EDSACwas completed at Cambridge University in 1949. This wasthe first computer to use a storage system other thanvacuum tubes or mechanical devices and consequentlyneeded far fewer vacuum tubes and therefore less powerthan its predecessors. Its memory system consisted ofacoustic mercury delay lines. The EDSAC contained only3000 vacuum tubes.

The National Physical Laboratory in London completedthe Automatic Calculating Engine or ACE in 1950. It used

Microwaves, Coaxial Gable, Computers 269

mercury delay lines and contained only 1000 vacuumtubes. A similar larger machine was built in the late 1950s.

Back in the United States, the Moore School of ElectricalEngineering built the EDVAC for the Ordnance Depart-ment of the U. S. Army in the early 1950s. It had mer-cury delay lines for its memory and contained about3500 vacuum tubes. The EDVAC was designed to handle44-digit binary numbers.

Eckert and Mauchly formed a company called the Eckert-Mauchly Computer Corporation, which produced the firstUNIVAC in 1951. This machine was equipped to use eight-channel metallic magnetic tape for its input, on which theinstructions were encoded by means of a typewriter key-board. Its storage section had both mercury delay lines andmagnetic tape. Output was recorded on magnetic tape fromwhich the results could be reproduced in printed form by aspecial typewriter.The first computer to use transistors instead of vacuum

tubes was the SEAC (Standards Eastern Automatic Com-puter) built by the U.S. Bureau of Standards at Washingtonin 1950. Except for the fact that transistors replaced vac-uum tubes, the SEAC followed to a large degree the logicaldesign of EDVAC. The SEAC was constructed in place atthe bureau, and was put in service in April 1950.

Transistors had not reached the degree of reliability in1950 that they attained later, and it was therefore not until1958 or 1959 that computer manufacturers generallyadopted the transistor. After the adoption of transistors, itbecame possible to reduce the size of computers verygreatly, and power requirements were tut to a fraction ofthose of the earlier computers.

Until the early 1950s nearly a11 computers had been builtfor government agencies or for universities. Later in thedecade and especially after the advent of transistors, indus-

270 Chapter Sixteen

tria1 and commercial concerns began to purchase computersin increasing numbers. The early computers were custom-built and were often designed for a specific purpose. Withthe widespread use of these devices came mass productionand the designation of computer types by manufacturer’smode1 numbers.

MEMORY SYSTEMS

Every calculating machine must have some sort of memory.It may consist merely of certain mechanical settings, as inthe early machines, or energized vacuum tubes, punchedcards, punched tape, electrical or acoustic delay lines,minute electrostatic charges, or, most commonly in moderncomputers, some form of magnetic memory. Magnetic re-cording had its beginning in a patent issued to ValdemarPoulsen of Denmark on December 1, 1898, covering amethod of recording a telephone message on a steel wire bymagnetizing the wire in tiny spots along its length to cor-respond with the undulations of the telephone crurent.Poulsen had little commercial success with his invention atthe time. Following World War 1, wire recording apparatuscame on the market, but the quality of reproduction waspoor. Magnetic tape began to replace steel wire for record-ing in the late 1930s. Magnetic tape consists of a plasticbase of Mylar or cellulose acetate 0.0007 inch to 0.0015inch thick. The magnetic coating consists of a finely dividedoxide of iron mixed with a plastic binder applied to thebase to a thickness of from 0.0004 inch to 0.0007 inch.Magnetic disks or drums are made in a somewhat similarway; a binder mixed with an oxide of iron is applied to thesurface of a disk or drum.

In order to encode information magnetically on any oneof these devices, a small electromagnet called the writing

Microwaves, Coaxial Gable, Computers 271

head is used, which is energized by electric currents underthe control of punched cards, punched tape, or by othermeans. The same or a similar small electromagnet, calledthe reading head, is used to reproduce the encoded infor-mation.

Magnetic cores are different, both in composition andmethod of application, from the other magnetic memorydevices. Magnetic cores were invented by Dr. Jay W. For-rester and were first used around 1950. They are very smallbeads of ferrite material, strung on lattices of intersectingwires. When currents of sufficient strength are sent throughthese wires, the selected cores are magnetized in the desireddirection. A current less than a certain threshold value Willnot produce a magnetomotive force sufficient to change thedirection of magnetization of a tore. In order to “pulse” atore a current of slightly more than one-half the thresholdamount is sent through each of two wires that intersect atthe desired tore. The two electromagnetic fields combine atthe one particular tore resulting in a change in its magneti-zation. The other cores along both wires receive less thanthe threshold current and are not affected. This process iscalled the “coincidence current selection system” and wasinvented by Dr. Forrester.

The ferrite material used in the cores is an important dis-covery of Dutch scientists employed by the Philips Com-pany in Holland during the Second World War. Since thattime ferrites have found many important applications, notonly as cores, but also in high-frequency transformers. Per-haps the simplest way of describing a ferrite of the kindmost useful in computer and other applications is to saythat it is a compound in which one of the iron atoms inmagnetite (FesOJ) has been replaced by a different metal-lit atom such as Mn, Cd, CO, Zn, Ni, CU, or Mg. The result-

272 Chapter Sixteen

ing compound is one having the composition MnFe2 04, orNiFe 04, or other similar compounds with other metals, orin some cases mixtures of metals. Ferrites are not metallicbut resemble ceramic materials in appearance, brittleness,and hardness. They are shaped by molding and grinding.

The characteristics of ferrites that make them desirable foruse in memory devices and for other purposes are that theyhave a nearly rectangular hysteresis loop, have high elec-trical resistance and therefore low eddy current losses, havehigh permeability, and have low coercive force. Their re-sponse to magnetic impulses may be measured in micro-seconds.

The various kinds of memory systems have inherent ad-vantages and disadvantages involving such things as cost,space required, and most important what is called accesstime, or the time required to retrieve a given bit of informa-tion. Paper tapes, punched cards, and magnetic tapes arerelatively cheap, but access time is rather long, because inthe case of tapes the entire tape must be scanned for thedesired information. Magnetic disks are also inexpensive but

are limited in capacity, and access time is rather long. Mag-netic drums have shorter access time but are more expen-sive, and they are bulky. Magnetic cores are the most ex-pensive but have by far the shortest access time, and a vastamount of information cari be stored in limited space.

INPUT AND OUTPUT SYSTEMSThe input to a computer may be for the purpose of givinginstructions or programming, or may be designed to giveinformation to the interna1 storage or memory system. Themethod used may take many forms such as keyboard,punched cards, punched paper tape, magnetic tape, drums,disks, cores, or any number of other methods. In program-

Microwaves, Coaxial Gable, Computers 273

ming a computer it may be given new information, or itmay be called upon to make use of its interna1 memorysystem.

The output from a computer may also take many formssuch as those mentioned for input, or the results may beprinted or shown on a screen. The computer may also beused to perform such tasks as check sorting, check writing,directing the operations of a machine or process, billing,bookkeeping, on-line teller service, and hundreds of otheroperations under the general heading of automation orcybernetics. Utility meter readers now use special pencils torecord meter readings, a process called mark sense. Suchrecords cari be read by a computer that then prepares thebills and at the same time makes totals of whatever figuresare desired.

NUMERATIONCalculators and the earlier computers used the decimalsystem. As work progressed on these devices it became ap-parent that a computer using the binary system was con-siderably less complicated and less expensive to build thanone using the decimal system. Computers employ suchthings as switches, vacuum tubes, transistors, and manymagnetic devices, a11 of which generally have only twostates: on or off, positive or negative, or in general what iscalled flip-flop. Because these devices, as they are used incomputers, have only two positions, they are therefore bestadapted to the binary system, which uses only the numbers1 and 0 in a very large number of combinations to representany rational number. Each binary 1 or 0 in the memorysystem or elsewhere is called a bit. The number 9 in binarynotation is 1001 and therefore consists of four bits.

Dr. Stibitz employed the biquinary system (a combination

274 Chapter Sixteen

of binary and quinary used to produce the equivalent ofdecimal numbers) in his 1937 computer. Some of the ear-lier computers had made limited use of the binary system.The ENIAC, which was the first electronic computer, stillused the decimal system in its memory, but practically a11later computers were entirely binary.

At the time the ENIAC was under construction, Dr. Johnvon Neumann, who was then at Los Alamos, Dr. Herman H.Goldstine, who was at the Aberdeen Proving Grounds, andArthur W. Burks of the Philosophy Department of theUniversity of Michigan wrote jointly a series of reports onthe subject of computers that became classics in computerhistory. The first of these appeared on June 28, 1946. Thisseries of reports greatly influenced the course of develop-ment of computers, as for example, in the matter of storedprograms and the use of the binary system.

17

Plasmas, Masers, Lasers, Fuel Cells,Piezoelectric Crystals,

Transistors

The behavioral characteristics of free electrons in the threestates of matter have similarities as well as differences. Afourth state in which electrical phenomena may occur mustbe added, namely, a partial or complete vacuum.

PLASMAS

The term plasma has been applied in recent years to ionizedgases. A wide range of conditions is embraced under thegeneral term, ranging from gases in the sun and stars, whosetemperatures are measured in millions of degrees, to thefrigid outer atmosphere of the earth. Plasmas may exist athigh temperatures and pressures or at lower values of both,but most of the familiar phenomena occur in the lowerranges.

There is nothing new about the phenomena themselvessince they include such things as the experiments of Hawks-bee with partially evacuated electrified glass globes, theglow of mercury vapor in the Torricellian tube, the electricarc, flames, lighting tubes using gases, the aurora, and manyother examples. Plasmas are usually electrically neutral inthat they contain equal numbers of positive and negativeions.

MASERS AND LASERSA maser is an amplifier or generator of electromagneticwaves. The name is an acronym derived from the descrip-tive title Microwave Amplification by Stimulated Emissionof Radiation. A laser is a similar device except that ordinarylight waves are used instead of microwaves. Masers employ

276 Chapter Seventeen

gases as a medium, while lasers may use gases, liquids, or

solids. It is characteristic of masers and lasers to emit coher-ent radiation, that is, radiation that is almost entirely of asingle frequency and that is of the same phase. The beamconsists of rays that are SO nearly parallel that the diver-gence is only about one second of arc.

The explanation of maser or laser action is to be found inPlanck’s quantum hypothesis, Bohr’s theory of the energylevels of electrons in different orbits, and Einstein’s postula-tion in 1917 that it is possible to cause electrons to jumpfrom one orbit to another and in the process to absorb orgive up energy in discrete quanta or photons. As an exten-sion of these theories it occurred to several scientists that itshould be possible to excite the atoms of a confined gas byapplying outside stimulation in the form of electromagneticwaves. The stimulated atoms would then radiate electro-magnetic waves of a frequency characteristic of the gasbeing used. &y reflecting these waves back and forth therewould be an increasing excitation of the atoms until theaction ,became strong enough to deliver part of the energyexternally. The external energy is supplied by the stimula-tion, and there is therefore no violation of the law of theconservation of energy.

Among those who had been considering such matters wereNicholaas Bloembergen of Harvard, N. G. Basov and A. M.Prokhorov of Lebedev Institute of MOSCOW, and C. H.Townes of Columbia University. It was Townes who firstsucceeded in producing an operational maser in 1953. Heand his students were already familiar with the microwaveemission characteristics of ammonia gas. By stimulating theatoms of ammonia gas contained in a metal box, whosedimensions were such as to produce resonance at the re-quired microwave frequency, they succeeded in producing a

Masers, Fuel Cells, Transistors 277

strong microwave beam of a single frequency. The actionwas similar to that which occurs in cavity resonators such asthe magnetron and klystron.

In 1952 while Townes and his associates were at work onthe ammonia maser, Basov and Prokhorov pointed out thepossibility of constructing a “molecular generator” to aconference on radio spectroscopy. In 1954 they publishedthe theory underlying a device such as the maser built byTownes, and in late 1955 or early 1956 they operated sucha device. For their accomplishments in this field the Rus-sians shared a Nobel Prize with Townes in 1964.

Maser or laser action depends upon the ability of the ap-paratus in use to propel a majority of the electrons, in theatoms of whatever medium is employed, into higher orbits.This process is called population inversion. The electrons inthe excited state may have been lifted one step to the nexthigher orbit or two steps to the second higher orbit. In thefirst case we have a two-level device and in the second case,three-level. The original ammonia maser was two-level. In1955 Basov and Prokhorov proposed a three-level gasmaser, and the following year Bloembergen announced hisideas on a three-level solid state maser.

Following the original ammonia gas maser, there were sev-eral years during which there appeared to be little progressin this field, but there was nevertheless considerable re-search, and many papers were written on the subject. In1957 H. E. D. Scovil and his associates developed a para-magnetic maser, and in 1958 Makhov, Kikuchi, Lambe, andTerhune obtained maser action in ruby. The most impor-tant paper published during this period appeared in theDecember 1958 issue of Physical Reuiew written byDr. Arthur Schawlow and his brother-in-law, Dr. Charles H.Townes, entitled “Infrared and Optical Masers.” The term

278 Chapter Swenteen

optical maser was replaced by laser in 1960. The paperdealt with optical masers in general and also proposed theconstruction of a maser in which the medium was to bepotassium vapor. A maser of this type was constructed but

it failed.At a symposium on quantum electronics held at High

View, New York, in September 1959, Schawlow proposedan optical maser in which the medium would be a solid inthe form of a rod with polished ends and open sides. Heused as an example a ruby rod and discussed its possible usein an optical maser.

The actual construction of the first ruby laser was thework of T. H. Maiman of the Hughes Aircraft Company. Itcontained a synthetic ruby rod only 4 centimeters in lengthand )/2 centimeter in diameter. It was pumped by a spiralxenon flash lamp that emitted short bursts of light of aboutl/icee second duration followed by intense flashes of redlaser light from the rod with a momentary power out-put of 10,000 watts. This achievement was announced byDr. Maiman at a news conference in New York on July 7,1960.After the first ruby laser there was feverish activity in

many laboratories. More powerful ruby lasers were builtwithin a few months, and the field of experiment widenedto include many new types. For solid state lasers such mate-rials as neodymium-doped glass, neodymium-doped cal-cium, calcium tungstate, and dysprosium-doped calciumfluoride were used successfully in place of ruby. Othertypes of masers and lasers included semiconductor andsingle- and two-gas types. Liquids were used also.

GAS LASERS

At the Bell Laboratories three Young scientists, Ali Javan,

Donald R. Herriott, and William R. Bennett, Jr., were en-

Masers, Fuel Ce&, Transistors 279

gaged in research on a two-gas laser at the time the rubylaser was announced. The American Telephone and Tele-graph Company’s immediate interest in laser work was thepossibility of using such devices in communications. Thetheory underlying this research had been conceived byJavan, and Herriott and Bennett developed the design ofthe apparatus, which consisted of a quartz tube 40 incheslong filled with a gas mixture, at low pressure, containingten parts helium and one part neon. Inside the tube at eachend were adjustable mirrors to reflect the light back andforth. Pumping was accomplished by means of three elec-trodes on the outside of the tube that were energized by aradio-frequency generator. This laser first became operativeon December 13, 1960, about six months after the rubylaser announcement.

Other combinations of the noble gases were tried success-fully and also carbon monoxide, carbon dioxide, andcesium vapor. The gas lasers operate at low temperaturesand are especially suited to communications work. They aregenerally very inefficient, but for the uses to which theyhave been put the low efficiency is not very important.

APPLICATIONS

Laser applications have been growing at a tremendous rate,and it would be difficult to foresee what the future mayhold. Lasers have been built that have momentary power out-puts as high as a billion watts and are capable of welding,piercing, or fusing the hardest materials. They cari producetemperatures far exceeding those on the surface of the sun.Lasers are finding uses in surgery, dentistry, and biochem-ical research. One such use is in welding a detached retina.They are also used for making measurements of extremeaccuracy, both microscopic and macroscopic, as for ex-

280 Chapter Seventeen

ample the measurement of earth movements for predictingearthquakes. The frequency rate of lasers is SO precise thatthey cari be used to make time measurements that would bealmost free of error over periods of many years.

It is believed that in the field of communications it maybe possible to transmit millions of messages simultaneouslyover a single laser beam, but there are still great difficultiesto be overcome. Lasers Will very probably be another pow-erful tool in the physics laboratory as well as in chemicaland biochemical laboratories. There cari be no doubt thatmankind Will reap rich rewards from laser research andtechnology.

ELECTROLYTIC AND

ELECTROCHEMICAL PHENOMENA

Electrochemistry had its beginning with the invention ofthe electric battery by Alessandro Volta. That discoverywas followed shortly by the important researches of Ber-zelius of Sweden and the work of Sir Humphry Davy and ofFaraday. Since that time great industries have been builtupon these discoveries, and there has been steady progressdue to the efforts of thousands of researchers.

There have been no spectactular new developments in thisfield in recent years but rather a constant refinement ofolder methods. The most noteworthy recent developmentshave been the production of better types of primary bat-

teries for longer life and greater reliability and new experi-ments with the fuel cell.

. .The prmcrple of the fuel ce11 is not new, because as earlyas 1839 William Grove of England made such a ce11 usingoxygen and hydrogen for fuel. What is new is the develop-ment of fuel cells into practical forms, suitable for certainlimited applications. Up to this time the cost has been toogreat to compete with other forms of electrical generation.

Masers, Fuel Ce&, Transistors 281

Fuel ce11 efficiency is high as compared with that of steamor interna1 combustion engine plants, running as high as 60to 70 percent, compared with 40 percent or less for thebest modern steam plants.

Fuel cells resemble other primary batteries in some re-spects but differ from them in other ways. Various materi-als are used for plates in fuel cells such as platinum orplatinum-plated carbon. The plates are immersed in an acid,Salt, or alkaline electrolyte. Oxygen and hydrogen are fedinto the ce11 where these gases combine to form water andin the process produce an electric current. The action is thereverse of that which takes place in the electrolysis ofwater. Other fuels such as propane, natural gas, methyl alco-hol, kerosene, and gasoline have also been used but at muchhigher temperatures. Fuel cells using acid or salt electrolytesoperate at ordinary temperatures, but cells using certainalkalies may operate at the melting point of the elec-trolytes.

Up to this time the fuel ce11 has had very limited applica-tions, the most noteworthy of which has been its use inspace capsules, beginning about 1966. The Allis-ChalmersCompany experimented with fuel cells in the 1950s fordriving a tractor, but not on a commercial basis. Experi-mentation in this field is still in progress by many com-panies in the United States and Europe, but nowhere hasthe fuel ce11 reached the production stage. Because of itshigh efficiency there is hope that it may be possible toproduce a low-cost design. An inexpensive fuel ce11 wouldhave a multitude of applications, not the least of whichwould be the propulsion of vehicles.

PIEZOELECTRICITYpiezoelectricity is the name given to a phenomenon inwhich a crystal becomes electrified by pressure. The prefix

282 Chapter Seventeen

piezo is from a Greek verb meaning to press. The effect wasdiscovered at the Sorbonne in Paris in 1880 by Pierre andJacques Curie. Piezoelectricity is closely related to pyro-electricity, a phenomenon discovered by Aepinus in 1756and defined as electrification by heat that often occurssimultaneously with piezoelectricity.

For many years piezoelectricity was merely an interestingphenomenon, and no practical applications were made of ituntil 1916 when Langevin attempted to use the principle asa submarine detection device but with little success. DuringWorld War 1 Walter G. Cady of Wesleyan University in Mid-dletown, Connecticut, discovered that mechanical reso-nance of vibrating crystals produced weak alternating cur-rents of corresponding frequency. This discovery ledshortly to the quartz crystal frequency control devices usedby radio stations. Beginning in 1925 the Bell TelephoneSystem used crystals to control frequencies for its multi-channel lines.

Piezoelectric crystals were applied to microphones andphonograph pickup cartridges, for which purpose it wasfound that Rochelle salts were admirably suited. Much ofthe research on these applications was carried on by theBrush Development Company of Cleveland, beginning in1930.Around the year 1940 Arthur von Hippel and his col-

leagues at Massachusetts Institute of Technology discoveredthe strong piezoelectric properties of crystals of bariumtitanate (BaTiOs), lead metaniobate (PbNb*Ob), and leadtitanate zirconate (Pb(TiZr)Os). These crystals were soonput to use for many of the more common applications, butfor frequency control and for wave filters the preferredmaterial was still quartz.

Masers, Fuel Ce&, Transistors 283

SOLID STATE DEVICESSome of the most noteworthy accomplishments in elec-trical science have corne in this field in recent years. Theterm solid state device is often incorrectly used as a syno-nym for semiconductor. The correct concept is muchbroader and includes besides semiconductor devices and ox-ide rectifiers such things as resistors, transformers, reactors,and such other devices as cari control electrical currentswithout moving parts, heat, light, or vacuum gaps.

SEMICONDUCTORSThe distinction between conductors and insulators has beena long-accepted fact, but the reasons for the differenceshave not been understood until recently, and even todaythere is a great deal of mystery surrounding them. Exactlyhow a current of electricity flows through a wire still pre-sents problems. It seems clear that there is a migration offree electrons from atom to atom, impelled by an electro-motive force. A displacement of one electron in an atom byanother occurs, but it is also clear that this movement ofelectrons cannot take place at the speed of light, a factwhich leads to the conclusion that the electromagnetic fieldis the real carrier of electrical energy.

Semiconductors, as the name indicates, may be conduc-tors or nonconductors, depending upon the temperature inintrinsic semiconductors or upon the electrical bias imposedupon the crystals from without in impurity semiconduc-tors. Among the most commonly used semiconductor mate-rials are germanium, silicon, and gallium arsenide. In thepure state these substances are nonconductors, but with theaddition of very small amounts of certain impurities theycari become semiconductors.

284 Chapter Seventeen

The theory behind this behavior may be stated briefly asfollows: The binding force that holds atoms together toform molecules and molecules together to form crystalsresides in the outer ring of electrons in the atom, and thenumber of such charges determines the valence of the atom.Normally, when the valence bonds to other atoms are satis-fied, the atom has no loosely held electrons in its outerring. If, however, an impurity is added that has a differentnumber of electrons in the outer orbit, there Will be eitheran excess or a deficiency of electrons in the valence bondsof the crystal. When there is an excess the semiconductor issaid to be n-type, and when there is a deficiency the semi-conductor is p-type. In the region where the latter condi-tion exists there is said to be a hole. A junction betweenn-type and p-type semiconductors Will pass a current inonly one direction. The impurities are different for variouskinds of crystals. Those most commonly used are arsenicand aluminum.

TRANSISTORSBell Telephone Laboratories had been working on the prob-lem of providing a cheaper and better electronic switchingdevice than the vacuum tube for some years with littlesuccess. In 1947 two of the researchers at Bell Laboratories,Walter H. Brattain and John Bardeen, succeeded in produc-ing a low-frequency amplifier using a piece of silicon im-mersed in a Salt solution. A month later they substituted abit of germanium for the silicon and again succeeded inproducing amplification. Research continued at an acceler-ated pace until in June 1948 the first transistor was madeby inserting three pointed wires into a piece of germanium.Two of these wires were part of an external circuit, and thethird, when connected to a battery, provided a bias voltage

Masers, Fuel Cells, Transistors 285

in much the same manner as is used with the grid of avacuum tube. The bias voltage must be sufficient to over-corne the counterpressure, or barrier within the crystal.With the required bias voltage a current cari be made toflow through the crystal as through any other conductor.

A third member of the Bell Telephone Laboratories teamwas William 0. Shockley, who had developed the theoryunderlying transistor behavior. In 1949 he published anarticle in the Bell System Technical Journal entitled “TheTheory of p-n Junctions in Semiconductors and p-n Junc-tion Transistors.” The term junction as it was used in thearticle and as it is generally understood is the contact areabetween regions in a crystal having p and n characteristics.Such a junction has the properties of a rectifier.

The original transistors were not satisfactory, because itwas not possible to make them by inserting wires in acrystal with any degree of uniformity, and they were noisyand mechanically weak. In Shockley’s article he proposedthat the transistor could be much improved by using asingle crystal into the faces of which the necessary im-purities were introduced. Firm connections could then bemade at the required points, eliminating the unreliable wirecontacts. The first such transistors were introduced com-mercially in 1951, but production in quantity was still notpossible because silicon and germanium contained traces ofunwanted impurities that interfered with satisfactory per-formance. These were later found to be gold in silicon andcopper in germanium, in such small quantities as to defychemical analysis.

The impurities problem was solved in 1954 when Wil-liam G. Pfann, a metallurgist at Bell Laboratories, discovereda new method of refining silicon and germanium thatyielded products of very high purity. TO accomplish this re-

286 Chapter Seventeen

suit a long piece of the material was heated in a narrow zoneby means of a high-frequency field. The molten zone wasmoved slowly along the length of the bar. It was found thatthe impurities were swept along ahead of the melted sub-stance, leaving almost perfectly pure material behind. Whenthe entire length of the bar had been covered in this man-ner, the impurities were concentrated at one end and couldbe removed.

With these purified materials transistors of excellent qual-ity were produced in 1955. There were further improve-ments in manufacturing following one upon another, suchas producing a junction in a single crystal during growth.Slices tut from such a crystal could be made into transis-tors. A more common method was to form junctions byputting small dots of the required impurity on oppositesides of a thin piece of crystal and baking at a temperaturehigh enough to cause the impurities to penetrate the surfaceof the semiconductor material. Later in 1955 the diffusiontechnique was introduced in which a slice of germanium orsilicon was heated in an atmosphere containing a vapor ofthe desired impurity, with the result that a very smallamount of the impurity was deposited upon the semicon-ductor and penetrated into it. This method, far superior toany previously employed, was used in the production ofuniform commercial transistors. What was even more im-portant, it was possible to manufacture transistors thatwere capable of operating at frequencies in the hundreds ofmegacycles.

THE TRANSISTOR INDUSTRYPractically a11 of the early development work on transistorswas done at Bell Laboratories or at Western Electric Com-pany. In 1949 the Bell Company was under pressure from

Masers, Fuel Cells, Transistors 287

the federal government to divorce the Western ElectricCompany, its subsidiary. Partly because of this pressure andpartly for other reasons, Western Electric Company offeredto license other manufacturers to produce transistors bypaying a flat fee of $25,000. Later the field was thrownwide open without the payment of a fee.

This wide-open situation in the transistor industry causeda rapid growth, SO that by 1954 there were twenty-five ormore manufacturers in the field in the United States whowere carrying on research. Although the Western ElectricCompany had a big lead at first, some of the competitorssoon developed advanced technologies that caused the in-dustry to progress at a tremendous rate. Among those whomade significant contributions to transistor science andtechnology were Texas Instruments, RCA, Philco, Transi-tron, General Electric, Westinghouse, Hughes, Sylvania, andRaytheon.

Electrical manufacturers and research laboratories in for-eign countries were soon engaged in transistor work andmade contributions of immense value. Dr. Leo Esaki, theJapanese physicist, invented the tunnel diode, in which gal-lium arsenide was used as a semiconductor. European labo-ratories in Holland, Germany, England, and France werealso engaged in meaningful research at an early date.As a result of Dr. Esaki’s work the General Electric Com-

pany produced a gallium arsenide transistor that was capa-ble of frequencies of 4000 to 5000 megacycles. Experi-ments have been conducted with many other semiconduc-tor materials including bismuth telluride, tungsten carbide,silicon carbide, and even diamond.

The transistor has made possible the production by themillions of portable radios. It has made available small por-table transmitters, walkie-talkies, and very small tape re-

288 Chapter Seventeen

corders. Transistors have replaced vacuum tubes to a largeextent for such varied uses as radio, television, telephoneequipment, and computers. The transistor has led to thedevelopment of miniaturization by the use of integratedcircuits in which entire circuits including transistors, resis-tors, capacitors, and their connections are etched on tinychips. A whole new field called microelectronics has beenborn making possible not only a reduction in size and costbut also increased reliability and an extension of the Upperfrequency range.

18

Atomic Energy, Government Research,Nuclear Fusion

ATOMIC ENERGYScientists had suspected since 1 8 9 8 t h a t t h e a t o m con-tained large amounts of energy that in some cases could bereleased, and they also surmised that matter and energywere mutually convertible. It was in 1898 that the Lorentztransformations based on the Michelson-Morley experi-ments were announced. The equivalence of matter andenergy was further emphasized by Einstein in 1905, atwhich time he made public his now-famous equation E =mc2 Actual proof of the availability of such energy camewith the experiments of Rutherford in 1919 and again in1932 by Cockroft and Walton, when they succeeded. insplitting the lithium atom. In 1932 also, N. Feather, an-other British scientist, succeeded in splitting the nitrogenatom by bombardment with neutrons.

Enrico Fermi, professor of physics at Rome, discovered in1934 that when uranium atoms were bombarded with neu-trons the uranium became radioactive, and in 1937 hefound that the radioactivity was due to the creation ofseveral isotopes of uranium.

Otto Hahn and Fritz Strassman of Berlin discovered in1939 that in the Fermi experiment not only were isotopesproduced, but uranium atoms were split to form pairs ofother elements having atomic weights about half that ofuranium. Accompanying this split there was the release of alarge amount of energy.

The various isotopes of uranium were found to be fission-

290 Chapter Eighteen

able in varying degrees. A slow neutron is sufficient to splita U-235 atom, whereas to split a U-238 atom requires a fastneutron. Based on the knowledge that vast amounts ofenergy were available from the atom, it became evident thatunder the proper conditions a chain reaction would be pro-duced. In order to test these theories, it was necessary toobtain a quantity of one or more of the readily fissionableisotopes of uranium. The separation of a small quantity ofU-235 was first accomplished by A. 0. Nier of the Univer-sity of Minnesota in 1939, using a modified Aston massspectrograph. Experiments with this material proved be-yond a doubt that such fissionable isotopes could indeedprovide energy in undreamed of amounts.

Nuclear research using accelerators, or atom smashers, asthey were called at the time, began to yield important re-sults in the transmutation of elements and in the produc-tion of isotopes. As early as 1919 Rutherford producedoxygen and hydrogen from helium and nitrogen with theuse of natural radiation by alpha particles from a radioac-tive source. In 1932 Cockcroft and Walton, who were re-searchers in the Cavendish Laboratory at Cambridge underRutherford, obtained helium from hydrogen and lithium inthe first accelerator experiment. Their apparatus was apuny affair compared with the many-million-volt accelera-tors of a few years later. Powerful accelerators were re-quired to reach the nuclei of the heavy elements such asuranium.

Within a very short time after the completion of theseaccelerators, very significant results began to appear. In1937 Perrier and Segrè discovered the element technetium,which had been produced by the bombardment of molyb-denum with neutrons or deuterons.

Atomic Energy, Government Research, Nuclear Fusion 291

Francium was discovered by Mlle Marguerite Perey in1937 as a disintegration product of actinium.

Neptunium was first identified by P. H. Abelson and Ed-win M. McMillan in 1939. It was produced by the bombard-ment of U-238 with slow neutrons and was the first of thenew transuranium elements.

Astatine was found in 1940 as the result of the bombard-ment of bismuth with alpha particles by Corson, MacKen-zie, and Segrè.

Plutonium, one of the more important new elements, wasdiscovered in 1940 by Kennedy, McMillan, Seaborg, Segrè,and Wahl. It is formed by the decay of neptunium.

Other elements discovered during this period or a littlelater included americium, curium, berkelium, californium,einsteinium, fermium, and mendelevium. Nearly a11 ofthese new elements were discovered at Berkeley by re-searchers who in addition to those already mentioned in-cluded Glenn T. Seaborg, Joseph W. Kennedy, Ralph A.James, Leon 0. Morgan, and Albert Ghiorso.

NUCLEAR RESEARCH FOR

THE UNITED STATES GOVERNMENTHahn and Strassman of Germany split the uranium atom in1939, the year in which World War II began. Scientists whowere familiar with the possibilities presented by this dis-covery feared that Germany might put together an atomicbomb which would have terrible consequences for the Al-lied cause.

The fears were presented to President Roosevelt in a letterwritten by Albert Einstein on October 11, 1939, but theproblem was already under attack in many laboratoriesthroughout the United States and also in England. At thebeginning of the year 1940 the only readily fissionable ma-

292 Chapter Eighteen

terial was U-235 and the problem was to find methods ofconcentrating the 0.7 percent of U-235 that occurs natu-rally in uranium. By the end of the year a new fissionableelement, plutonium, was discovered.Altogether four possible methods of separating U-235

were under consideration. These were the gaseous diffusionprocess, begun at Columbia University; the thermal diffu-sion process, invented by P. H. Abelson and under test atthe Naval Research Laboratory, near Washington; the cen-trifugal process at the University of Virginia; and the massspectrograph, electromagnetic, or calutron process at Berke-ley.

In order to coordinate these scattered efforts, the NationalDefense Research Committee was appointed in June 1940,under the leadership of Dr. Vannevar Bush who was suc-ceeded a year later by Dr. James B. Conant. Progress wasslow, and it was not until May 1942 that the committeemet to decide which method would produce the greatestquantity of U-235 in the shortest time. The committee wasunable to make a choice and decided, therefore, to buildfacilities using three of the available methods: gaseous dif-fusion, centrifuge, and calutron. Before the plant was built,however, the centrifuge method was dropped.

The committee’s recommendation was accepted by theWar Department and Colonel James C. Marshall of the Man-hattan Engineer District was selected to head the project,which came to be known as the Manhattan Project. Withina short time Brigadier General L. R. Groves succeeded Colo-nel Marshall; his principal assignment was the constructionof the facilities needed for the large-scale production ofU-235 and later of plutonium.A group of leading nuclear scientists was assembled at the

University of Chicago where the new Metallurgical Labora-

Atomic Energy, Government Research, Nuclear Fusion 293

tory had been completed. The primary purpose of thisgroup was to build an atomic pile or self-sustaining reactor.This group was headed by Dr. Arthur H. Compton and in-cluded Enrico Fermi, Glenn Seaborg, Isadore Perlman, LeoSzilard, Eugene Wigner, Herbert Anderson, Walter Zinn,and Samuel Anderson. The Argonne National Laboratory,which was under construction at this time, was to house theproposed reactor, but when construction of Argonne wasdelayed it was decided to build a smaller one under thestands at Stagg Field. Work on this reactor was begun onNovember 7, 1942, and it went into service on the after-noon of December 2,1942.

The Oak Ridge, Tennessee, plant for the separation ofU-235, which included a new town for its workers, wasrushed to completion. At first it contained only the gaseousdiffusion and calutron separation facilities. The calutronportion was first to go into operation, and although it didproduce U-235 it was found to be inefficient. The gaseousdiffusion plant went into operation January 20, 1945, andit, too, was rather disappointing at first.

After it was found that production fell short of the de-sired quantities, it was decided that if partially enricheduranium could be fed into the production lines the processwould be speeded up considerably. The decision was made,therefore, to build a thermal diffusion plant that wouldyield uranium enriched to at least double the naturalamount of U-235. The new plant was ready in late 1944.A plutonium plant, called the Hanford Engineering Works,

was built in the State of Washington. It was begun in March1943 and, in addition to the plant, included housing forthousands of workers. In the production of plutonium on alarge scale, as in the laboratory, U-238 is bombarded withslow neutrons to form neptunium that then decays to pro-

294 Chapter Eighteen

duce plutonium. In order to carry out this process on aproduction basis, a very large reactor was built. After onlyeighteen months spent on construction, Hanford was ready.The reactor went critical a few minutes after midnight onSeptember 27, 1944, but it had operated only a few hourswhen it gradually failed. Some time passed before thetrouble was found, when it was discovered that the reactorwas poisoned by xenon 135. Fermi finally determined thatthe difficulty could be overcome by operating the reactorat a higher rate. Production was resumed on Christmas Dayof 1944.

LOS ALAMOS LABORATORY

AND THE ATOMIC BOMBThe Los Alamos (New Mexico) Laboratory was begun inMarch 1943, at which time scientists from many universi-ties in the United States were brought together under theleadership of J. R. Oppenheimer. The purpose of this groupwas to construct an atomic bomb. While they knew, in ageneral way, what was required to put together such a de-vice, no one had any precise information as to what consti-tuted a critical mass of uranium or how the componentscould be brought together in the exceedingly brief time of afew millionths of a second. These problems were solved,one by one, with the greatest of tare. The first experi-mental bomb was exploded at Alamogordo, New Mexico, at5:30 A.M., July 16, 1945. On August 6, 1945, an atomicbomb was dropped on Hiroshima, Japan, and three dayslater a second bomb obliterated Nagasaki.

ATOMIC ENERGY COMMISSIONIn July 1946, b ta ou a year after the end of the war, theCongress of the United States established the Atomic En-

Atomic Energy, Government Research, Nuclear Fusion 295

ergy Commission, which since that time has had the respon-sibility of providing radioactive materials, not only for mili-tary purposes, but more importantly for peacetime uses. Intwenty years atomic energy became competitive with coaland other fossil fuels, and there has been a tremendousexpansion in medical uses of radioactive materials, openingan entirely new field in medical practice. The use of radio-active materials as tracers has found wide applications, notonly in medicine, but also in plant genetics and even inindustry.

NUCLEAR POWER PLANTS

Nuclear power plants are electric generating stations thatuse radioactive materials for fuel. They produce heat byatomic fission and generate steam for the operation of tur-boelectric generators. Eight basic types of reactors for usein these plants have been operated or tested experimentally.These are pressurized water, boiling water, sodium graphite,fast breeder, homogenous, organic cooled and moderated,gas cooled, and high temperature gas cooled.

Reactor assemblies, in addition to the fuel tore, contain acoolant such as water, gas, liquid metals, or other materialsto carry the heat from the atomic pile to a heat exchanger.In the case of a boiling wat& reactor, however, steam isgenerated directly in the reactor tank. Reactor assembliesalso include a moderator, which is most commonly water orgraphite, and finally there must be provision for control,which is usually accomplished by means of control rods.

The moderator is designed to change the fast neutrons,with velocities averaging 10,000 miles per second, to slow(or thermal) neutrons, having velocities of about 1 mile persecond. The slow neutrons are much more effective in split-ting U-235 atoms than the fast neutrons.

Control rods are necessary to hold the rate of fission at

296 Chapter Eighteen

the level required for power demands or to shut down thereactor. There are other methods of controlling the produc-tion of heat but control rods are the most commonly used.They may be composed of boron steel, boron carbide,gadolinium, samarium, or other materials.

In the United States the fuel used in nuclear reactors ismost often enriched uranium containing from 1.5 to 5 per-cent U-235. In B&ain natural uranium metal is used inmost cases because the facilities for the production ofU-235 are not sufficient for the purpose.

When a U-235 atom is split, about 2.5 neutrons are re-leased on the average, but some of these are lost. At leastone of the neutrons must be available for splitting anotheratom if the chain reaction is to be maintained.

Most of the nuclear power generating stations in theUnited States are of the pressurized-water or boiling watertype. In England, which at present has most of the world’snuclear generating capacity, gas-cooled reactors have beenused exclusively. The gas employed has been mostly carbondioxide, but with higher temperatures in the newer plants ithas become necessary to change to helium.

The first large-scale nuclear power plant in the world wasCalder Hall in England, which began operating in October1956. In the United States the first nuclear power plantdesigned solely for power generation was the Shippingportstation in Pennsylvania, which began the production ofelectricity on December 2, 1957. Calder Hall was a gas-cooled plant using carbon dioxide and Shippingport was apressurized-water plant.At the end of 1966, England had 4,048,OOO kilowatts of

nuclear generating capacity in operation, and the UnitedStates had 1,956,OOO kilowatts. At that time, new capacityunder construction or planned was 5,290,OOO kilowatts in

Atomic Energy, Government Research, Nuclear Fusion 297

England and 9,285,OOO kilowatts in the United States.At the end of the year 1969, the United States had5,235,OOO kilowatts of nuclear capacity in operation andhad 65,365,OOO kilowatts under construction or planned,with the latest completion date set at 1977 but with mostof the capacity to be ready by 1974.

NUCLEAR FUSION

Although the energy liberated in nuclear fission is verygreat, the energy available from nuclear fusion is evengreater but much more difficult to achieve. Fission occursin the heavier elements, whereas fusion is possible only inthe lighter elements, notably hydrogen and tritium (thetriple mass isotope of hydrogen). Helium apparently cannotbe used in the fusion process, but it is an end product offusion. It is possible that lithium may be suitable for thispurpose. The great difficulty in achieving fusion is that itrequires temperatures in the millions of degrees and veryhigh pressures. Such conditions prevail in the interior of oursun and in the stars, but SO far a controlled fusion processhas been impossible. Hydrogen bombs have been explodedwith the use of an atomic bomb to trigger the reaction.Much work has been done in seeking a method of using thefusion process for the production of useful energy, but it isevident that no substance on earth could contain a fusionreaction at the required temperatures and pressures. SO farthe most promising method is one in which the requiredconditions are obtained by confining the process within apowerful magnetic field (pin& effect), but the solutionseems a long way off.

WHITHER

When Joseph Priestley, back in the eighteenth Century,wrote his book, The History and Present State of Electric-

298 Chapter Eighteen

ity, he predicted that new developments in electrical sci-ence would far outstrip anything yet conceived, but someof his contemporaries were sure that nothing more could belearned about the subject. Considering the advanced stateof electrical science today, we might be forgiven if we be-lieved that man had reached the limit of his capabilities inthis direction, but we must recognize that each new stephas uncovered more questions than it has provided answers.Therefore, if the past is in any way a guide to the future,we may be sure that still greater achievements lie ahead. Aswe view the accomplishments of the last half Century weare amazed at the ability of men of science to learn ofthings which the “eye hath not seen nor ear heard.” At thesame time every truly great scientist must view with awe,wonder, and admiration the great works of creation, whosemysteries he has explored.

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8Mabee, Carleton. The American Leonardo: The Life ofSamuel F. B. Morse. New York: Octagon Books, 1969.Morgan, A. P. The Pageant of Electricity. New York:Appleton-Century, 1939.

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10Carty, John J. Annual Report of the Smithsonian Institu-tion. Washington: Smithsonian Institution, 1922.Mackenzie, Catherine. Alexander Graham Bell. Boston andNew York: Houghton Mifflin CO., 1928.Prescott, George B. The Speaking Telephone. New York:D. Appleton CO., 1879.

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13Hammond, John Winthrop. Men and Volts. New York:J. B. Lippincott CO., 1941.Houston, Edwin J. Electricity in Everyday Life. Vols. 2and 3. New York: P. F. Collier and Son, 1904-1905.Norris, Henry H. Electric Railway Practice in 1925. NewYork: American Railway Association, 1926.

14Dunlap, Orrin E., Jr. Radio and Teleuision Almanac. NewYork: Harper, 1951.F.C.C. Bulletins. 2-B, 3-G, 11-S. Washington: U. S. Govern-ment Printing Office, 1966 and 1968.F.C.C. Rules. Updated annually or oftener, Vols. 2 and 3.Washington: U. S. Government Printing Office, 1970.Jones, Charles R. Facsimile. New York: Murray Hi11 BO&,1949.Radio Corporation of America. The Birth of an Industry.New York: RCA, n. d.Schera a, M. G., and Roche, J. J. Video Handbook. Mont-

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INDEX

Abacus, 262Abelson, P., 291,292Aberdeen Proving Ground, 266,274

Académie des Sciences, 233Accelerators, 290. See also Vande Graaf generator; Cyclotron;Betatron; Synchrotron; Linearaccelerator

Access time, 272Actinium, 234Aepinus, F. U. T., 28,282Affel, Herman A., 260Aiken. Dr. Howard. 266Air pu’mp, 11, 162,‘224,225Albertus Maenus. 6Alchemy, 6 -Aldini, Giovanni (1762-1834)35,39

Alexanderson, E. F. W., 207,208,209

Alliance CO., 73, 74Alhs-Chalmem CO., 281Alpha rays, 234,235,244,248-250,290,291

Alternating current, 71, 156,177, 180, 183-187, 197,200,210,217,221,226,282

Alternating-current generators,71,73,156,177,183,187

Alternating-current motor, 177,1 8 6

Aluminum, 230,284Aluminum Company of Amer-ica, 187

Alvarez, L., 252Amateur radio, 204,209, 213Amber, 4, 5, 18American Bell Telephone CO.,

1 5 0American Institute of ElectricalEngineers, 186,206

American Marconi CO., 209American Speaking Telephone

CO. . 146

American Telephone and Tele-graph CO., 150, 151,209,219,220,279,286

Americium, 291Ammonia, 276,277Ammonium chloride, 78,80Amp&e, André Marie (1775-

1836), 48-56, 54, 63, 88, 96,1 9 8

Ampere (unit), 93Amplifier, 206, 210, 217, 221,248,257,258,275,284

Amplitude modulation (AM),212

Amsier, 263Amstutz, Noah S., 216Analog computer, 267Analytical Engine (Babbage’scomputer), 265

Anderson, C. D., 244Anderson, Herbert, 293Anderson, Samuel, 293Anderson, Sergeant (Faraday’sassistant), 56

Anglo-American Cable CO., 128Angstrom (unit), 240,246,247Anion, 60Anode, 60,224,229Antenna, 201,257,258,260Antimony, 82Apps, A. , 180Arabs, 5,6,7Arago, Franpis Jean (1786-1853), 49, 50, 54, 56, 59, 63,66,105

Arc lamp mechanism, 153Arc hght, 73, 152-157, 160,164, 165, 177, 181, 182, 185,1 9 4

Arc light generatoq 153, 154,1 6 8

Argonne National Laboratory,293

Aristotle, 4Armature, 74

308 Index

Armstrong, E. H. (1890-1954)207,214,215

Arsenic, 284Astatic needle, 48Astatine, 291Atlantic Cable, 116, 117, 121,

126,129Atlantic Telegraph CO., 118,128Atmospheric electricity, 26, 27Atom, 235, 237, 240-245,276,277, 283, 284. See also Atomicenergy

Atomic energy, 249, 289, 291.See alro Atomie power

Atomic Energy Commission,252,294

Atomic power, 295,296,297Atom physics, 233,243,245Attraction, 13, 14, 15, 18,26Audio, 222Audion, 206Aurora borealis, 14,22,275Automatic Calculating Engine,268

Automatic Sequence ControlledCalculator, 267

Autotransformer, 178

Baader, 225Babbage, Charles (1792-1871),264,265,266,268

Bache, A. D., 66Bachhoffer, C. H., 179Bacon, Sir Francis (1561-1626),10,ll

Bacon, Roger (1214-1294), 6,10

Bailey, F. C., 185Bain, Alexander, 101,215Baird, John, 220Bakewell, Frederick, 216Balmer, J. J., 240, 242Bamboo, 164,165,172Bardeen, John, 284Barium, 44,282Barium platinocyanide, 230Barlow, Peter, 50

Barlow’s wheel, 50, 59, 75Bartbolomew, H. G., 217Basov, N. G., 276,277Battery, 41-44, 46, 57, 58, 63,64, 77-82, 84, 87, 96, 100,108, 109, 122, 131, 144, 152,161, 178, 192, 199, 204, 210,215,248,280,281,284

Beams, J. W., 252Beccaria, Giovanni Battista(1716-1781), 27,30,46

Becker, H., 244Becquerel, Alexandre E., 237Becquerel, Antoine Henri( 18521908), 233,234,237,239

Bell, Alexander Graham (1847-1922), 113,132-151,198,199

Bell Telephone Association, 145,150

Bell Telephone CO., 150Bell Telephone Laboratories,151,246,255, 260,262,266,278,284,285,286

Bendix Corp., 255Bennet, Abraham (1750-1799),28,82

Bennett, William R., Jr., 278,279

Bentley, Edward W., 185,193Bergmann and CO., 168Berkelium, 291Berliner transmitter, 148Berzelius, J&s Jakob (1766-

1852), 44,60,198,280Beta rays, 234,239,248,250Betatron, 250,251Bevis, Dr. John( 1693-1771) 19Bidwell, Shelford, 216Binary system, 268, 269, 273,274

Biot, Jean Baptiste (1774-18623,49,54,88,89

Biquinary system, 273Bismuth, 57,291Bismuth telluride, 287Blake transmitter, 148Bl&ry, 0. T., 182

Index 309

Branly, Eduard (1844-1940). 200

Bloembergen, Nicholaas, 276Bohdner, 263Bohr, Niels (1885-1962) 241,242,243,276

Bolton, Dr. Werner von, 173Borda, Jean Charles(1738-1799), 31

Bom, M., 243Boron, 44Borries, von, 246Bothe, W., 244Bound charge, 28,221Bourseul, Charles, 131Boyle, Robert (1627-1691), 11,14,224

Boze, Georg, 14,46Brackett, Frederick S., 242Bragg, William H., 232,234Bragg, W. L., 232Brahe, Tycho (1546-1601) 11

Brush dynamo, 156,157,158Brush Electric CO., 157,194Brushes, 59,195Brush-Swan, 172bye, J. W., 266Bubble chamber, 247, 248Bunsen batteries, 153,162Bunsen, Robert Wilhelm (1811-1899), 79

Bu&s, Dr. Arthur W., 274Burroughs Corp., 264Busch, Hans , 245Bush, Dr. Vannevar, 266,292

Cadmium, 80,81,238Cady, Walter G., 282Calcium, 44,278Calculator, 262,263,270,273Calder Hall, 296Caldini, Leopoldo (1725-1813)

Brantford, Ontario, 134, 135,137,140,143,144,147

Brattain, Walter H., 284Braun, Karl F. (1850-1918),219,224,254

Breit and Tuve, 250Bremer, 160Brett, John W., 117, 118, 119Bright, Charles, 118,119, 181British Association for the Ad-vancement of Science, 90

Broadcasting, 211,212,253Broadcasting stations, 210,211,

2 1 3Broglie, Louis de, 243,245Brookhaven National Labora-tory, 252

Brown, George, 140Brown, Gordon, 141Bruche, Ernst, 245Brugmans, Sebald Justin, 32Brugnatelli, Luigi, 43Brunsviga calculator, 263Brush, Charles F., 82, 156Brush arc lamps, 154Brush Development CO., 282

Cahfomium, 291Callan, N. J., 178,181

3 4

Calutron, 292,293Candlepower, 159, 160, 171,

1 8 2Canton, John (1718-1772), 24,

2 8Capdcitance. Sec CapacityCapacity, 93,122,253,255Carbon, 32, 44, 79, 80, 148,153, 154, 156, 160, 161, 162,204,243,281

Carbon dioxide, 279,296Carborundum, 204Carey, G. R., 218Carlisle, Sir Anthony (1769-

1840), 41,96Carpentier, Jules, 181Caselli, Giovanni, 2 16Cathode, 60, 224, 227, 229,230,233,246,248,256

Cathode ray, 227, 229, 230,232,239,246

Cathode-ray tube, 219, 224,253,254,257

Cation, 60

310 Index

Cavendish, Henry (1731-1810)19,30

Centennial Exposition, 142Cesium, 217,220, 238, 279cgs system, 89Chadwick, J., 244Chain reaction, 290,296Channel, 213, 222, 223, 259,260,269,282

Chapin, D. M., 237Chinese, 2, 3, 5Chlorine, 44Ch&ie, Samuel H., 87Clark ce11 (standard cell), 80, 92Clarke, E. M., 71,72Claude, Georges, 174Cleveland Telegraph Supply CO.,

1 5 6Clockwork, 100,153, 215,216Cloud chamber, 247Coaxial table, 260, 261,262Cobalt, 32Cockroft, J. D., 249,289,290Coherer, 200,201, 203. See olso

Branly, Eduard; Marconi,Guglielmo

Collecter, 18Color television, 222Colpitts, Dr. Edwin H., 214Communication, 8, 95, 117,122, 200, 212, 258, 260, 261,262,279,280

Commutator, 59, 71, 73, 75,182,183,185,192,195,197

Compass needle, 2, 7, 8, 9, 46,48,50, 56,59,95

Compton, A. H., 243,293Compton, Karl T., 250Computers, 262,264-274,288Computing, Tabulating and Re-

cording CO., 264Conant, Dr. James B., 292Condenser, 180,215,221Conductivity, 154, 173, 200,204,205

Conductors, 17, 28, 32, 48, 49,

51,55, 87, 119, 127, 152, 171,237,283,285

Conradi, G., 263Continuous waves, 207Control Data Corp., 264Controller, 197Converter, 182Converter, rotary, 177Cooke, Sir Thomas William(1806-1879) 104,112

Coolidge, Dr. William D., 174,233

Cooper, Peter, 117Copernicus, Nicolaus (1472-1543), 8,11

Copley Medal, 27Copper oxide, 80Copper plating, 154Copper sulfate, 78, 79Corne& Ezra, 107,110,115Corpuscle, 205,230Cosmic rays, 244,245Cosmotron, 252Coulomb, Charles Augustin de(1736-1806), 29, 30, 31, 50,88,89

Coulomb (unit), 90,93,198Counter electromotive force, 44,65. See also Polarization; Self-induction

Couronne des tasses, 39,41Crookes dark space, 229Crookes, Sir William (1832-

1919), 205,227,228,229Crookes tube, 205, 224, 225,226, 230, 233, 235, 246, 247,253

Cruikshank, William, 41,108Crystal, 232,284,285,286C@al, piezoelectric, 281, 282Crystal detector, 203, 204, 205Crystallography, 233Crystal Palace, 171Crystaf receiver, 210,214Cuprous oxide, 237Curie, Irène, 244Curie, Jacques, 282

Index 311

Curie, Marie (1867-1936). 205. tor; Mercurv detector: Transis2 3 4

I

Curie, Pierre (1859-1906), 234,2 8 2

Curium, 291Cycles, 73, 184-189, 251Cyclotron, 250,251

Daft, Leo, 194Dalibard, Thomas Frangois, 22D’Alincourt, 215Dal Negro, Salvatore, 71Daniell, J. F., 66,77Daniell battery, 77,78,108Dark Ages, 5,6D’Arsonval, J. F., 87,130Davenport, Thomas, 75,192Davidson, Robert, 75,192Davisson, C. J., 243Davy, Sir Humphry (1778-1829), 41, 42, 44, 45, 52, 54,55,60,68,152,198,280

Day, R. E., 237deCaus, Solomon, 11.de Changy, 161Decimal system, 273,274Decomposition, 41De Forest, Lee (1873-1961),205,206,207

de Hondt, Francis, 216Deleuil and Archereau, 153Delor, M.. 22De M&a;te by William Gilbert,8.9.11

de’M&itens, 181$en;o$d2ate, 257

Des&iers, Jean, 17de Sauty, 127Descartes, René (Cartesius)(1596-1650), 11

Desprez, Marcel , 181Detector, radio. See Coherer;Crystal detector; Electrolyticdetector; Fleming valve; Hot-wire detector; Magnetie detec-

tor; Vacuum tube.Detector, radiation. See Bubblechamber; Cloud chamber;Geiger-Müller counter; Ioniza-tion chamber; Photocell;Photographie plate; Photo-multiplier; Radiometer;Scintillation counter;Spinthariscope.

Dial telephone, 151Diamagnetism, 32,60Dielectric, 60Difference Engine, 265Digital computew, 267Digital Equipment Corporation,264

DiB-White Act, 212Dipping needle, 8Dira~, P. A., 243Direct crurent, 71, 73, 177, 183,185,202

Dissector tube, 219,220,221Dolbear electrostatictransmitter, 148

Dominion Telegraph CO., 143Dom Pedro, 143Doppler effect, 258Driver, W. R., 150Dry battery, 80,81Duboscq, 153Duddell, W. B., 202Du Fay, Charles (16981739),17, 20, 24, 26

Duhamel, Jean Baptiste, 21Dunwoody, Gen. H. H. C., 204Duplex telegraph, 112Durfee, B. M., 267Dyar, Harrison Gray, 96, 101Dynamoelectric machine (dy-namo), 74, 77, 82, 84, 114,152,166-169,171,184,192

Dyspros ium, 278

Eckert, Dr. J. P., 268Eckert-Mauchly Computer Corp.

264,269

312 Index

Edelkrautz, 225Edison, Thomas Alva, (1847-

1931), 113,162-171,183-185,193,194,198,199,204,205

Edison carbon transmitter, 146,147,148

Edison effect, 204, 205,206Edison Electric Ilhrminating CO.,

168Edison Electric Light CO., 164,

168.Edison Electric Lighting Com-

pany of London, 171Edison-Lalande battery, 80Edison Lamp CO., 167Edison lamps, 167, 171Edison Machine Works, 168,171Edison screw base, 167, 171,

1 7 2Edison transmitter, 146-148EDSAC, 268EDVAC, 269bpt, 1,334Einstein, Albert A. (1879-1955),

239,276,289,291Einsteinium, 291Electric Accounting Machines(CO.), 264

Electrical energy, 59Electrical machines (electro-

static), 11-14, 18, 19,26, 32,34, 42, 46,77,82, 83, 174,199,226

Electrical units, 89Electric arc, 44, 152Electric current, 41, 42, 46,48,

49, 51, 55, 82, 131, 152, 160,174,271,283

Electric doubler, 30Electric field, 20, 26, 88, 89,

2 3 9Electric lighting, 152, 155, 156,

157,160,165,171,177,192Electic railway, 75, 192, 193,

194Electric Railway CO. of the

u. s., 193

Electric Telephone CO., 145Electrified body, 24, 26, 27, 28Electrochemical quivalent, 60Electrochemistry, 60, 73, 96,

280Electrode, 44, 60, 77, 78, 79,

80, 83, 153, 224, 226, 237,238,250,251,252,279

Electrolysis, 60,281Electrolyte, 60,77,81, 237,281Electrolytic detector, 201, 203Electrolytic process, 177Electromagnetic induction, 59,64,67,71,139,148,177

Electromagnetic units, 89, 90,92,93,94

Electromagnetic waves, 198,199, 200,202, 232,234,235,247,253,256,275,276

Electrometer, 30Electromotive force, 44, 51, 65,

73,90,283Electromotive series, 41,77Electron, 4, 205,220, 221,224,

230, 233, 237-246, 248-251,256,275,277,283,284

Electron gun, 220, 251Electronic computen, 262,268,

274Electronic television camera, 219Electron microscope, 245, 246,

247,276Electrophorus, 28, 35, 37Electroplating, 43, 177Electroscope, 9 , 21, 28, 30,

234,247Electrostatic induction, 27Electrostatic machines. See Elec-

trical machinesElectrostatic units, 89, 90, 92,

9 3 . 9 4Elevated rods, 24, 26, 27Elster, J. P., 204Emission, 238, 242Emitron, 220Enclosed arc lamps, 160ENIAC computer, 268,274

Index 313313

Esaki, Dr. Leo, 287Espenschied, Lloyd, 260

Facsimile, 21.5, 216,218,258Farad, 90,93Faraday, Michael (1791-1867),49, 50, 52-61, 64-66, 71, 73,75, 88, 89, 119, 178, 198,199, 226,229,280

Farmer, Moses G. (1820-1893),74,113,161,162,192

Farnsworth, Philo, 219Faure, Camille, 82Feather, N., 289Federal Communications Com-mission (FCC), 212, 213, 222,2 5 9

Federal Radio Commission, 212Federal Telcgraph CO., 203Federal Telephone CO., 255Fermi, Enrico (1901-1954), 289,293,294

Fermium, 291Ferrant$ S. Z. de, 154Ferraris, Gahleo, 185Ferrites, 271,272Fessenden, R. A., 203,207Field, Cyrus (1819-1892), 116,117,118,126,127

Field, Stephen D., 193Filament, 60, 162,164, 165,166,204,205

Finney, Dr. Joseph R., 194Fischer, J. C., 107Fission, 290, 295,297Fizeau, Armand (1819-1896)92,180

Flaming arcs, 160Fleischauer, E., 263Fleming, J. A., 205Fleming valve, 205, 206Floating compass, 7Fluorescence, 83,174,175,225,226,230,235,247

Fluorescent lamps, 83,175,176Fluorine, 44Foppl, 92

Forbes, George, 187Forbes, George, 187Forbes, J. Malcolm, 150Forbes, J. Malcolm, 150Forbes, Col. William H., 150Forbes, Col. William H., 150Forrester, Dr. Jay W., 271Fort Wayne lamps, 172Foucancourt, Sigerus de, 7Francium, 291Franklin, Dr. Benjamin (1706-1790), 20, 22-28, 30, 33, 46,66,75

Franklin, William S., 207Franklin Institute, 103Freeman, H. M., 210Frequency, 135, 184, 185,189,202, 210-212, 215, 222, 223,238, 239, 243, 257, 258, 259,276,280,282,284,288

Frequency modulation (FM),213,215,222,257

Frequency shift, 257, 258Friedrich and Knipping, 232Frischen, 113Fuel cell, 280, 281Fuller, G. S., 237Fuller, J. B., 181Fuller battery, 80

Gaede air pump, 225Gale, L. D., 101, 104,107, 110Galena crystal, 204Galilei, Galileo (1564-1642), 11Gallium arsenide, 283,287Galvani, Luigi (1737-1798), 34

37,39,199Galvanometer, 50, 57, 65, 85,87,96,122,129, 204,248

Gamma rays, 234,244,248Gardincr, Samuel, 161Garrett, George S., 156Gasfilled lamp, 174Gaulard and Gibbs, 181, 182,

1 8 3Gauss, Johann Karl Friedrich(1777-1855), 88,89,90,198

Gauss (unit), 93Gautherot, Nicholas, 42

314 Index

Gay-Lussac , Joseph Louis(1778-1850), 54,105

Geiger, Hans, 235, 248Geiger-Müller counter, 247,248Ge&ler, Heituich (1814-1879),83,224

G;k;lei26ubes, 83, 174, 224,

Geitd, H., 204Gem lamp, 172General Electric CO., 171, 174,

188, 209, 233, 246, 251, 255,264,287

Generator, 171Germanium, 283,284,285,286Germer, L. H., 243Ghiorso, A., 291Gibbs, Josiah Willard. See Gau-lard and Gibbs

Gilbert, Dr. William (154C1603), 8-11,14,21, 30

Gilbert (unit), 93Gintl, Wilhelm, 112Giorgi, 92Gisborne, F. N., 115-118Glass, Elliott CO., 119, 120Glass insulator, 95, 108Gold, 1, 42, 285Gold leaf electroscope, 28, 30Goldstein, Eugen, 227Goldstine, Dr. Herman, 274Gordon, 14Goudsmit, Samuel A., 242Gower, Fred, 145Graham, George, 31Gralath, Daniel, 30Gramme, Zenoble Theophile,74, 75, 76, 154, 156

Graphite, 162, 184, 295Gravity battery, 78Gray, Elisha, 113,137, 142, 146Gray, Stephen, 15, 16, 17, 20,

21, 28, 30, 95Great Eastern, 127, 128Greece, 3, 4, 5, 6,8,31, 134Green, George, 88Grenet battery, 80

Grid, 206, 207, 256, 285Grove, Sir William Robert(1811-1896), 79, 161, 180,181,280

Grove battery, 79, 108,161Groves, Gen. L. R., 292Gudden, B., 238Guericke, Otto von (1602-

1686), 11, 12, 13, 30, 48, 224Gulcher, 154Gunter, Edmund, 263Gutta-percha CO., 119

Hahn, Otto, 289,291Hall process, 187Hallwaehs, 238Hamilton, 21,33,75Hamilton, F. E., 267Hanford Engineering Works,293,294

Hansen, W. W., 252Hare, Dr. Robert, 43Harmonies, 202Harmonie telegraph, 113, 135-

1 4 0Harrison, C. W., 181Harrison lamp factory, 167, 171Hartley, 214Hawksbee, Francis, 13, 22, 28,

152,224,225,275Hazeltine, Louis Alton, 214, 255Headphones, 210, 213Heaviside, O., 92, 94Hefner and Alteneck, 154Heisenberg, W., 243H;n7rm, 235, 279, 290, 296,

Helix, 48-50,57,58Helmholtz, Hermann Ludwig

von (1821-1894) 88,132,198,202

Henley, William T., 30Henry, J. C., 194Henry, Joseph (1797-1878), 50,61-71, 75, 88, 96, 138, 178,198,199,202

Henry (unit), 93

Index 315

Herriot, Donald R., 278,279Hertz , Heinrich (1857-1894),198, 199, 200, 202, 230, 233,238

Heterodyne, 214, 257Hewitt, Peter Cooper, 173Higginson, H. L., 150High frequency, 207-210, 221,271,286

Hinds, Ketchum and CO., 167Hindenberg, 225Hippel, Arthur von, 282Hittorf, Johann WiIhelm, 204,227

Hjorth, Soren, 74Hollerith, Dr. Herman, 263,

264Holmes, F. H., 73Holmes Burglar Alarm CO., 146Holtz, Wilhelm, 82, 83Honeywell, 264Hooke, Robert, 88Hopkinson, John, 182, 185Horsecars, 191Horsepower , 73Hot-wire detector, 201, 203House, Royal E., 111, 112House Printing Telegraph CO.,110,112

Houston, Edwin J., 156Huang-ti, 2Hubbard, Gardiner Greene, 135-

138,140-145,148Hubbard, Mabel, 135, 140, 145Hubbard, William, 143Hughes Aircraft CO., 278, 287Humboldt, Friedrich Heimichvon (1769-1859), 2, 54

Hunnings transmitter, 148Hunt, Wilson G., 117Huygens, Christian (1629-

1695), 11Hydraulic turbine, 186Hydrogen, 44, 73, 80, 240,241, 242, 249, 250, 280, 290,297

Hysteresis, 272

Iconoscope, 219,220, 221IIIumination, 221Image orthicon, 220, 221Incandescence, 161, 204Incandescent lamp, 60, 161-

165,167,168,182,183Incandescent lighting, 164, 168,169,171,185

Induction, 28, 30, 34, 59, 66,82,83,101,200, 253,256

Induction CO~I, 101, 126, 146,147, 174, 178-181, 198, 199,2 2 6

Induction motor, 184, 185, 186Infrared, 242, 277Ingenhousz, Dr. Jan, 18Insulated wire, 50, 58, 63, 84,

102,107,114,115,261Insulators, 16, 17, 25, 28, 63,80,84,95, 114, 122, 126, 130,156,283

Internai combustion engine, 177International Business Machines

Corp., 264, 267International Conference onRadio, 211

Intemationa Electrical Con-gress, 90, 92

International ElectrotechnicalCommission, 94

International Telephone andTelegraph CO., 151

Interpole motor, 197Interrupter, 178-180, 202, 226Iodine, 44Ion, 60, 250,275Ionization, 204, 275Ionization chamber, 247, 248Iron diaphragm, 131, 144Iron wire, 110, 115, 119, 127Islam, 5Isotopes, 289, 290

Jablochkov, Paul, 154,155, 156,177,181,182

Jackson, Charles S., 97Jacobi, Moritz Hermann, 75

316 Index

Jacquard loom, 264Jasinsky, 251Javan, Ali, 278,279Jean, M., 180Johannson, H., 245Joliot, Frédéric, 244Joseph, 34Joule, James Prescott (1818

1889), 88,89Just and Hanaman, 173

Kennedy, J. W., 291Kepler, Johannes (1571-1630),

11

Kohlrausch, R. H., 88, 92Konn, Stanislas, 161Korn, Dr. Arthur, 216Koupho, 5

Kerst, D. W., 250Kikuchi. 277Kilocycies, 211,213,261Kinescope, 219,222Kinnersley, Ebenezer, 26, 27Kirchhoff, Gustav Robert(1824-1877), 88

Kleist, E. G. von, 18, 48Klystron, 252, 256, 277Knight, Walter H., 185, 194Knight and Bentley, 185, 195,

1 9 6

Kroll, Max, 246Kriiger battery, 80

Ladd, 154Lake, C. D., 266Lalande-Chaperon battery, 80Lambe, 211Lane-Fox, 17 1Lange, 231Langevin, 28 2Langmuir, Dr. Irving, 174Laplace, Pierre Simon de (1749-1827), 96

La Rive, Auguste Arthur de(1801-1873), 66

La Rive, Charles Gaspard de(1770-1834), 54

Laser, 262, 275-280Laue, Max von, 232,235Lauffen-Frankfurt transmissionline, 188

Lavoisier, Antoine (1743-1794),31

Lawrence, E. O., 250Lead, sponge, 81,82

123, 152, 157, 217, 218, 220,

Lead dioxide, 82Leclanché, Georges, 79,80, 84

221, 225, 230, 232, 237, 238,

Leclanché batteries, 79, 80Lee, Higginson and CO., 150

240, 245, 249, 251, 253, 275,

Leibniz, Gottfried Wilhelm von(1646-1716), 11,263

2 8 3

Lemmonier, Pierre (1715-1799),19, 20, 27

Lenard, P., 205, 230, 235, 238,239

Lenz, Heinrich (1804-1865), 88Leyden jar, 18, 19, 22, 24, 25,

27, 32, 35, 39, 42, 48,66,67,95,152,161,179

Lichtenberg, Georg Christoph,3 1

Lieben, 206Light, 13-16, 21, 60, 67, 92,

Lighthouse, 60, 73Lighthouse tube, 256Lighting, 83,84, 171, 184Lightning, 5, 15,16,21,22, 33,

37, 46, 67, 261Linear accelerator, 252Lines of force, 32, 60L;t$m, 238, 249, 289, 290,

Locomotive, 190, 191, 192Lodestone, 2,4, 5,6,21Lodyguine, Alexandre de, 161Logarithmic scale, 263Lomond, Claude, 95Loomis lamps, 172Loran, 213Loren& H. A., 92, 94, 289

Index 317

Los Alamos Laboratory, 294Loudspeaker, 213Lowber, Robert W., 117Lucretius, 5Lumen, 160Lumens per watt, 160, 172, 175Lyman, T., 242

MacCauley, T. B., 179MacFarlane, M. L. D., 217MacKenzie, 291McMillan, Edwin M., 291Magnesia, 4Magnet, 4-7, 9, 21, 30, 46, 48,

49,50, 58, 64, 66, 73, 85, 123,247,251

Magnet, permanent, 48, 71, 72,87,144,256

Magnetic chariot, 2, 3Magnetic circuit, 85, 139, 181,

1 8 2Magnetic compass, 7. See also

Compass needleMagnetic cores, 271, 272Magnetic detector, 201,203Magnetic disks, drums, 270,272Magnetic field, 32, 46, 49, 59,88, 89, 199, 220, 227, 234,245,251,297

Magnetic measurement, 31,88Maguetic needle, 22, 48, 49, 57,85,95. See also Compass needle

Magnetic pole, 30, 49, 51, 55,72, 88, 92

Magnetic tape, 269, 270, 272Magnetic Telegraph CO., 110Magnetic units, 89, 93Magnetism, 2, 7, 8, 21, 22, 31,60

Magnetism, earth, 9, 31, 46, 48,55, 85, 87

Magnetite, 2, 271Magnetizing, 22, 64, 67, 270,

2 7 1Magneto, 71, 74, 82, 146, 152,

181Magnetometer, 31

Magnetomotive force, 10, 93,2 7 1

Magnetron, 255,256, 277Magnet wire, 58, 114Maiman, T. H., 278Makhov, 277Manganese dioxide, 80,81Manhattan project, 292Mannheim, Lt. Amédée. 163Marconi, Guglielmo (18741937), 200,201,202,203

Margentin, Perh Vilhelm, 22Maricourt, Pierre de, 7, 95Marine galvanometer, 123, 124,127,129

Mariotte, Edme, (1620-1684),11

Mark 1, II, III computers, 267,268

Marks, Louis B., 160Mark-sense recording, 273Marsden, E., 235Marshall, Col. James C., 292Maser, 275-278Massachusetts Institute of Tech-

nology, 136, 249, 255, 266,282

Masson and Bréguet, 179Mathematics, 6, 11Mauchly, Dr. John, 268Maxim, Hiram Stevens, 162,171Maxwell, James Clerk (1831-1879), 88,198,199,202

Maxwell (unit), 93, 241Mayer, Johann Tobias, 30Mazeas, Jean Mathurin (1716-

1801), 27Megacycles, 213, 222, 223, 256,258,259,286,287

Magawat ts , 256Meidinger, J. H., 78Meissner, 207, 214Memory, 265, 268, 269, 272,Mendelevium, 291Menlo Park, 162,164, 165,167,

1 6 8Mercury, 13, 14,48, 49, 50, 56,

318 Index

Mercury (continued)80, 81, 83, 92, 100, 174,179,225,226,227,275

Mercury arc lamp, 173, 175Mercury arc rectifier, 173Mercury delay lines, 268-270Mercury detector, 201, 203Meson, 245Metal filament lamps, 162, 172Metallography, 233Meteor i tes , 1Meyer, A. J., 1 1 3Mica, 180, 220, 221Miche& John, 21, 30Michelson, Albert A. (1852-1931), 289

Michelson-Morley experiment ,2 8 9

Microphone, 214,282Microscope, 235,247Microseconds, 257, 272Microwaves, 253-258, 275-277Middle Ages, 5,6Miletus, 3Millikan. Robert Andrews(1868-1953), 230,239

Miraud, 84mksa system, 94mks system, 94Modulation, 131, 215,221,260,261

Molecule, 245, 284Moleyns, Frederick de, 161Molybdenum, 290Moore, D. McFarlan, 174Moore School of Engineering,

266, 268Morley, Albert A., 289Morrison, Charles , 95Morse, Samuel F. B. (1791-

1872), 97-112, 115-120, 130,136,145,198,199

Morse code, 97, 100, 102, 103,209

Mosaic, 218, 220, 221Moseley, H. G. (1887-1915),243

Motor, 21,25, 74-77, 101, 182,185,192,194-197.

Motor-generator, 185,197Mount Ida, 4Mouromtseff, 1. E., 253Muirhead, 113Multiplex telegraph, 113, 202Multiplier, 50, 63Musschenbroek, Pieter van, 18

Napier, John (1550-1617) 11National Bell Telephone CO.,

1 5 0National Cash Register CO.,

2 6 4National Defense ResearchCommittee, 292

National Physical Laboratory,268

National Radio Conference, 211Nedden, 113Needle, steel, 2, 3, 7, 58, 59Neodymium, 278Neon, 174,218,279Neon tube lighting, 175Neptunium, 291,293Nernst lamp, 173Neumann, Dr. John von, 274Neutrino, 245Neutron, 244, 289, 290, 291,

293; 295,296Newall, R. S., and CO., 119,

1 2 0Newcomen, Thomas (1663-

1729), 11New England Telephone CO.,

146,150Newfoundland Electric Tele-graph CO., 118

Newton, Sir Isaac (1642-1727),11, 13,88

New York and Mississippi Val-ley Printing Telegraph CO., 111

New York, Newfoundland andLondon Telegraph CO., 117,1 1 8 .

Niagara Falls, 186, 188

Index 319

Nicholson, William (1753-1815), 41,96

Nickel, 81,200Nier, Dr. A. O., 290Nipkow, Dr. Paul, 218Nitric acid, 79Nitrogen, 289,290Nollet, Floris, 161Nollet, Jean Antoine, 20, 21,22,28,30

Nollet, M., 71, 73Nollet magnetos, 71-73, 152,154,177

Norman, Robert, 8Novum Organum by Francis

Bacon, 10Nuclear fusion, 297Nuclear power, 295Nuclear reactor, 293, 294, 295Nucleus, 235, 237, 241, 242,244, 249, 250, 290, 296, 297

Oak Ridge plant, 293Oersted, Hans Christian (1777-1851), 46, 47, 48, 55, 71, 96,1 9 8

Oersted (unit), 93Ohm, Gorg Simon (1787-1854), 51,89, 198

Ohm’s law, 41,50,88Ohm (unit), 90, 92, 93Oppenheimer, J. R., 244, 294Optical glass, 56Optics, 6Opus Majus by Roger Bacon, 6O;d&7’24& 242, 243, 256,276,

Orthicon, 220Oscillations, 202, 207Oscillator tubes, 207, 252, 256,257,258

Oscilloscope, 219, 224, 253Osmium lamp, 173Oxygen, 32, 73, 80, 280, 290

Pacinotti, Antonio, 74Page, Charles Grafton (1812-

1868), 71, 101, 178, 179,192

Page induction coil, 146, 178Panofsky, W. K. H., 252Papin, Denis, 11Paramagnetic, 60Particles, 48, 229,232-235,

243-245,247-249,252,290Partz battery, 80Pascal, Blaise (1623-1662), 263Paschen, F., 242Patten, 225Pauli, W., 243Pearlman, L, 293Pearl Street, central station, 167,

168,169,171Pearson, G. L., 237Pendulum, 100Pepys, William Hasledine, 30, 43Perigrinus, Petrus (Pierre deMaricourt), 7, 8

Permeability, 32, 272Perrier, 290Perrin, Jean, 229Pfann, William G., 285Pfund, 242Phase, 184,186188Philco, 255, 264, 287Philosophical Transactions, 14,

2 8Phonautograph, 136Phosphor, 222Phosphorescence, 226Photoconductivity, 237Photoelectric cell, 217, 247Photoelectric effect, 216, 237Photoelectron, 238, 239, 240Photoemission, 237,238,241Photograph, 31, 232, 233, 247Photomultiplier tube, 248, 249Photon, 239,240,276Photosensitive, 220Photovoltaic effect, 237Picard, Jean, 13, 152, 225Pickard, G. W., 204Piezo crystals, 282Piezoelectricity, 281, 282Pitchblende, 234Pithball electroscope, 30, 95

320 Index

Pittsburgh Reduction CO., 187Pixii, Hypolite, 71, 72, 198Planck, Max (1858-1947) 205,238,276

Plan&s constant, 238, 239Planimeter, 263Planté, Gaston, 81,82Plasma, 275Platinum, 49, 60, 79, 148, 161,

162,179,281Pliny, 4Plücker, Julius, 226, 227Plutonium, 291-294Poggendorff, Johann Christian(1796-1877), 50,63,85,180

Pohl, R., 238Poisson, Siméon Denis (1781-1840), 88

Polarization, 44, 77, 78, 80, 108Polarized bell, 146Polonium, 234Popov, Alexander S., 200,201Portrule, 100, 103, 105, 109Positron, 244Potassium, 44, 217, 238, 278Potential, 227, 237, 246, 249,

250Pouillet, Claude S. (1790-

1868), 85, 86, 88Poulsen, Valdemar, 202, 203,

270Poulsen are, 203, 207Preece, Sir William H. (1834-

1913), 113,201,205Priestley, Joseph (1733-1804)

32, 297Prime conductor, 14, 26Principia by Isaac Newton, 11,88

Programming, 266, 272Prokhorov, A. N., 276, 277Proton, 244, 249, 251

Quadrant electrometer, 30Quadruplex telegraph, 113Quantum, 238, 241, 243, 276,278

Quantum mechanics, 243, 245Quartz, 279, 282

Radar, 213, 253-258Radiant energy, 238Radiant matter, 227Radiation, 233, 234, 238, 240,241, 247,275,276,290

Radiation Laboratory, 255Radio, 200, 202, 207, 208, 212,

215, 217, 221, 233, 247, 253,254,258,277,279,288

Radio Act, 211,212Radioactivity, 224, 234, 235,247,249,289,295

Radio Corporation of America(RCA), 209, 210, 217, 219,220, 246, 253,255,264,287

Radiometer, 229, 247Radio receivers, 209, 210, 213,

214,287Radio regulation, 211, 212, 213Radio relay, 213, 253, 258,Radio station cal1 letters, 209,

212,213259,261,262

Radio stations, 210, 282Radio telegraph, 207, 211Radio telephone, 207Radio transmitter, 209, 213Radium, 234Radon, 234,235Railroad, 76, 113, 190, 191Railway signais, 80,84Railway telegraphs, 113Ramark, 213Ramsden, Jesse, 18Rankin, 182Rapid transit, 192Rappaport, Paul, 237Raytheon, 255, 264, 287Reactor, 293-296Reading head, 271Receiver, radio, 202, 210, 222,254,256

Receiver, telephone, 131, 132,139, 142, 143, 144, 148, 214

Index 321

Recorders, 214, 288Recording wire and tape, 214,270

Rectifier, 210, 285Regenerative circuit, 214Reiger, 239Reis, Johann Philip (1834-1874), 131,132, 137,148

Reisz, 206Reizen, 95Relay, 66, 101, 114, 266, 267Reluctance, 93Remington-Rand, 264Renaissance, 5, 8Repulsion, 13, 15, 18, 25, 28Resinous electricity, 18Resistance, 44, 51, 87, 88, 90,93,267,272

Resonance, 131, 202, 256, 276,277,282

Richmann, George William, 24Riemann, 88Ritchie, 180Ritter, Johann, 41, 42Roberts, Martyn John, 161Roberts , M. O., 117Rochelle salts, 282Roemer, Olaus, 92Romagnosi, Gian Domenico(1761-1835) 46

Rome, 1, 4, 5, 8Rontgen Wilhelm Conrad(1845-1923), 230-233

Rosin, 26, 28Rotary converter, 185, 197Rotor, 72Round, H. J., 207Royal Institution, 42, 44, 54,55,68

Royal Society, 22, 27, 39, 43,44, 46, 59, 205

Rubidium, 217, 238Ruby, 277-279Ruhmkorff, H. D., 179,180Rumford, Count. See Thomp-son, Benjamin

Ruska, Ernst, 246

Rutherford, Lord Ernest (1871-1937), 203,205,234-237,240,241,249,289,290

Rydberg, J. R., 240Rydberg constant, 240

Sanders, George, 135, 136Sanders, Thomas, 135-138, 140,

141,145,146,148,150Savart, Félix (1791-1841), 49,

88,89Savery, Thomas, 11Sawyer, William, 216Sawyer and Man, 161,162Saxton, 71Scanning, 215, 218, 219, 220,

222Scanning disk, 215, 218Scattering, 235, 237Schawlow, Dr. Arthur, 277,

278Schilling, Pawal L. (Baron), 96Schloemilch, W., 203Schmidt, G. C., 234Schottky, W., 237Schrodinger, E., 243, 245Schuckert, 154Schwartz, Berthold, 6Schweigger, Johann (1777-

1857), 50,63,85,96Scintillation, 235, 247, 248, 249Scovil, H. E. D., 277Seaborg, Glenn T., 291,293SEAC computer, 269Segrè, 290, 291Seitz, 239Selective Sequence Electronic

Calculator, 268Selenium cell, 216, 217, 218,

237Self-induction, 65, 71, 93, 178Sellon, J. S., 82Semiconductor, 278, 283-287Series circuit, 153, 160, 185Series motor, 185Shippingport, 296Shockley, William O., 285

322 Index

Siemens, Ernest Werner von(1816-1892) 74, 154, 182,185,192,193

Siemens and Halske, 113, 172,246

Sigerus, See FoucancourtSilicon, 204, 237, 283-286Silicon carbide, 287Silsbee, Francis B., 94Silver, 34, 35, 42, 57, 81, 200Silver, leaf, 19Singing arc, 202Siphon recorder, 129, 130Slepian, J., 250Slide rule, 263Sloan, D. H., 252Smeaton, John, 19, 224Smee, Alfred, 80Smith, F. 0. J., 103, 104, 116Smith, Willoughby, 216, 237Smithson, James, 68Smithsonian Institution, 68Socrates, 3Sodium, 44Sodium vapor lamp, 175Solar cell, 151Solid back transmitter, 148Solid state, 283Solon, 3Sommerfeld, 242Sommering, Samuel Thomasvon, 96

Sparks, 12, 15, 17, 18, 20, 24,25, 27, 35, 39, 42, 59, 75,152, 178, 179, 180, 202, 207,238

Specific inductive capacity, 60Spectral lines, 242Spectrograph, 232, 290, 292Spectroscope, 232Spectrum, 202, 217, 220, 222,

240,242,253Sperry Corp., 255, 264Sperry-Rand Corp., 264Spin, 242Spinthariscope, 229, 242Spottiswoode, 180

Sprague, Frank J., 185,193-196Sprague Electric Railway and

Motor CO., 194,195Sprengel mercury pump, 162,225

Squirted filament, 172Staite, W. E., 154, 161Standard cells, 80Standards Eastern AutomaticComputer (SEAC), 269

Stanley, William, 182, 183Stark, 113,239Starr, J. W., 161Stearns, J. B., 113Steel needle, 66Steenbeck, 251Steinheil, Karl, 96Stephenson, George, 190Stibitz, Dr. George R., 266Stock ticker, 112Stoney, Dr. G. Johnstone, 230Storage battery, 42, 81, 177,210

St&, 180Strassman, Fritz, 289, 291Strauss, 206Street lighting, 156, 157Street railway, 185, 190, 191,

192,195,197Strontium, 44Strowger, A. B., 151Sturgeon, William (1783-1850),50,63, 75, 179

Submarine table, 106,115-119Sulfur hall, 12,26, 27Sulfuric acid, 42, 79, 81Sulzer, Johann Georg (1720-

1779), 34Superheterodyne, 214Swammerdam, Jan (1637-

1682), 34Swan, Sir Joseph Wilson (1828-

1914), 82,161,162,171, 172,198

Swedenborg, Emanuel (16881772), 225

Sylvania, 287

Index 323

Synchronism, 215-218,222Synchrotron, 251

TabuIating machines, 261TantaIum, 217TantaIum lamp, 173Taylor , Moses, 117Tcheou-Koung, 2Technetium, 290Telautograph, 139, 140Telefunken, 203Telegraph, 20, 48, 64, 78, 83,84,95-116,118,120,130,135, 137, 138, 144, 200, 215,216

Telegraph, printing, 111, 112Telegraph, transcontinental, 114Telegraph code, 95, 97, 102Telegraph key, 109, 202Telegraph patent, 104,105, 110,

1 1 1Telegraph Plateau, 118Telegraph relay, 97, 101, 112Telegraph sounder, 96, 112Telephone, 80, 114, 131, 132,137-140, 142-147, 150, 151,200, 205, 248, 253, 258, 260,261,270,288

Telescope, 87Television, 212, 213, 215, 218,219,222,254,258,288

Television, electronic, 219Television, mechanical, 218-220Television camera, 219-222Temple of Juno, 5Temple of Solomon, 5Ten Eyck, P., 64Terhune, 277TesIa, Nikola, 186Texas Instruments, 287ThaIes, 3, 4, 46ThaIIium, 229Thebes, 3Theophrastus, 4Thermocouple, 204Thermometer, 247ThessaIy, 4

Thomas, Charles Xavier, 263Thompson, Benjamin (Count

Rumford)( 1753-1814), 54,68Thompson, SiIvanus, 87Thomson, Elihu, 156, 202Thomson, Sir Joseph John(1856-1940), 205, 230, 2382 4 1

Thomson, William (Lord Kelvin)(1824-1907) 88,90,119,123,127, 129, 143, 240, 266, 268

Thomson-Houston CO., 154,157,172,183,195,196

Thorium, 217,234Thunder, 15,17Tin, 1,19Topler, A. J. I., 82, 83, 225Torricelli, Evangelista (1608-

1647), 11, 13Torricellian tube (barometer),

13,152,161,225,275Torsion balance, 29, 30, 50, 89Townes, C. H., 276, 277Trackless trolley, 197Transformer, 66,177, 178,181-

183,207,271,283Transistor, 151, 259, 269, 273,284-288

Transitron, 287Transmission, 13, 15, 16, 19,20, 95, 129, 131, 137, 139,177, 181, 185, 187,188,215-218,221,258,261

Transmitter, radio, 214, 222,254,256-258,287

Transmitter, telegraph, 200,202,217

Transmitter, telephone, 131,139,141-143,148

Transportation, 190, 191, 192Triode tube, 206Tritium, 297Trolley, 194Tucker, S. M., 254Tuned radio frequency, 214Tungsten carbide, 287Tungsten drawn wire, 173, 174

324 Index

Tungsten lamp. 173, 174Tuning, 202,214Tuning fork, 134,135, 216Tunnel diode, 287

Uhlenbeck, George, 242Ultra high frequency (UHF),

223Ultraviolet light, 175, 229, 238-

240,242Underground Tube CO., 168UNESCO, 94Unit, 51, 85, 88, 89United Fruit CO., 209UNIVAC computers, 264, 269Uranium, 233, 234, 289-294,296

US. Naval Research Laboratory,254,292

U.S. Navy, 118, 120, 203, 264,267

Vacuum, 13, 14, 32, 161, 162,165,246,275,283

Vacuum chamber, 250, 251Vacuum tube, 217, 225, 226,227, 256, 268-270, 273, 284,285,288

Vail, Alfred, 101, 103, 104,107-110,136

Vail, Theodore N., 148,150Valence, 284Valentia, lreland, 118, 120, 122,

1 2 7Van de Graaf, R. J., 249Van de Graaf generator, 249,250

Van Depoele, Charles J., 185,193,194,196

Van Depoele Electric Manufac-turing CO., 194

Van Malderen, Joseph, 72Van Marum, Martin, 32Varian, Russell and Sigurd, 252Varley, Alfred, 74Varley, C. F., 82, 127, 181,

227,229Velocity of electricity, 19

Versorium, 9,30Very high frequency (VHF), 223Video, 221,222Vidicon, 220Vitreous electricity, 18Volckmar, 82Volt, 73, 78, 90, 92, 93, 188,

1 8 9Volta, Alessandro (1745-1827),28, 34, 37-39, 43, 54, 77, 82,96,152,198,280

Voltage, 73, 79, 126, 160, 161,174, 177, 183, 188, 189, 204,248,267,284

Voltaic cell, 32, 41, 42, 44, 77,152,161

Voltaic electricity, 20, 42, 44Volta’s pile, 39-41,43

Wade, W. G., 210Wahl, 291Wagner and Neef, 179Wall, Dr. William, 14, 21Wallace-Farmer, 154, 157, 162Walton, E. T. S., 249, 251, 289,

290Watson, Thomas A., 136, 137,

139,140,142,144-148Watson, Sir William, 19, 20, 24Watson-Watt, Robert Alexander,

2 5 5Watt, James (1736-1829), 11Waveguide, 253Wavelength, 199, 232, 238,240,

242,253,255,256,260Way, John Thomas, 161Weber, Wilhelm Eduard (18041

1891), 87-90, 92, 96, 130,1 9 8

Welsbach, Dr. Auer von, 173Western Electric CO., 151, 209,255,286,287

Western Electric ManufacturingCO., 137, 138, 151

Western Union Telegraph CO.,111, 114, 137, 138, 145-148,217

Westinghouse, George, 183, 186

Index 325

Westinghouse Electric and Manu-facturing CO., 172, 183, 187,209,210,219,253,255,287

Weston, 154, 157Weston standard cell, 80Wheatstone, Sir Charles (1802

1875), 66,74,104,198Wheatstone’s bridge, 87, 203Wheatstone telegraph, 96, 110,

112,113Wheeler, Granville, 16Whewell, William, 60White, A. C., 148White, Chandler, 117Whitehouse, Dr. E. 0. W., 119,

1 2 6Wideroe, 250,252Wigner, Eugene, 293Wilde, H., 74, 154, 181Wilke, 28Williams, Charles, 145Williams shop, 136, 137, 139,

140,142,144,145,151Wilson, Benjamin, 18, 21, 24,

33,75Wilson, C. T. R., 247Wimshurst, James, 82, 83Winckler, Johann, 14, 20, 21,

9 5Wingate, Edmund, 263Wire. See Insulated wire; Magnet

wireWiredrawing, 17Wireless detector, 206Wireless Ship Act, 211Wireless telegraph, 200-202Wireless Telegraph and Signal

CO., 201Wireless tuned circuit, 202Wolff, Dr. Irving, 253Wollaston, William Hyde, 43Wright and Staite, 154Writing head, 270

Xenon, 278,294X ray, 230, 232-234, 243,244,247,25 1

Yttrium, 173

Zinc disk, 39Zinc electrode, 77-79Zinc sulfate, 78, 79, 81Zinn, Walter, 293Zipernowsky, Carl, 182Zirconium, 173, 217Zworykin, Dr. V. K., 219, 246