Bence Jones, Michael Faraday the Life and Letter Volume 2

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Physical Sciences
From ancient times, humans have tried to understand the workings o
the world around them. Te roots o modern physical science go back to
the very earliest mechanical devices such as levers and rollers, the mixing
o paints and dyes, and the importance o the heavenly bodies in early
religious observance and navigation. Te physical sciences as we know them
today began to emerge as independent academic subjects during the early modern period, in the work o Newton and other ‘natural philosophers’,
and numerous sub-disciplines developed during the centuries that ollowed.
Tis part o the Cambridge Library Collection is devoted to landmark
publications in this area which will be o interest to historians o science
concerned with individual scientists, particular discoveries, and advances in
scientific method, or with the establishment and development o scientific
institutions around the world.
Michael Faraday (1791-1867) made oundational contributions in the
fields o physics and chemistry, notably in relation to electricity. One o the
greatest scientists o his day, Faraday held the position o Fullerian Proessor
o Chemistry at the Royal Institution o Great Britain or over thirty years.
Not long afer his death, his riend Henry Bence Jones attempted ‘to join
together his words, and to orm them into a picture o his lie which may be
almost looked upon as an autobiography.’ Jones’ compilation o Faraday’s manuscripts, letters, notebooks, and other writings resulted in this Life and
Letters (1870) which remains an important resource or learning more about
one o the most influential scientific experimentalists o the nineteenth
century. Volume 2 (1831–1867) describes his research on electricity and
electromagnetism, his work as a scientific adviser to the government and
industry and his service to education.
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Faraday V
B J
CAMBR ID GE UNIVER S IY PR ES S
Cambridge, New York, Melbourne, Madrid, Cape own, Singapore, São Paolo, Delhi, Dubai, okyo
Published in the United States o America by Cambridge University Press, New York
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© in this compilation Cambridge University Press 2010
Tis edition first published 1870 Tis digitally printed version 2010
ISBN 978-1-108-01460-1 Paperback
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VOL. II.
IN
TWO
VOLUMES.
right o translation in reserved
CONTENTS
T H E S EC O N D V O L U M E ,
CHAPTER
I.
1831-1S40.
To
MT.
49.
PAGE
F I R S T P E R I O D OF E L E C T R IC A L R E S E A R C H — D I S C O V E R Y OE M A G N E T O -
E L E C T R I C I T Y — I N D U C T I O N C U R R E N T S A K D D E F I N I T E E L E C TR I C A L
D E C O M P O S I T I O N . . . . . . . . . . 1
CHAPTER
—STVISS JOURNAL— NATURE OF MATTER ' . . . . 1 2 6
CHAPTER
III.
Mr
64.
L A T E R P E R I O D O F E L E C T R I CA L R E S E A R C H — D I S C O V E R T O F T H E
' M A G N E T I S A T I O N O F L I G H T ' T H E M A G N E T I C S T A T E O F A L L
M A T T E R — A T M O S P H E R I C M A G N E T I S M . . . . . . 1 9 3
CHAPTER IV.
1856-1867. TOJET.
ELECTRIC LIGH T
C G
LABORATORY
Frontispiece
T H E S T U D Y T T H E R O Y L I N S T I T U T I O N . . . . Patje 1
THE HAMPTON COUKT HOUSE WHEBE PAKABAY DIED . . 39 3
FARADAY S TOMB
. . . . 4 7 9
L I F E O F F A R A D A Y .
CHAPTER I.
NETO-ELECTRICITY •—• INDUCTION CURRENTS AND DE FINIT E
ELECTRICAL DECOMPOSITION.
IT will be the object of this chapter first to describe 1831.
the great scientific work which Faraday did at this
MrÎ
period ; secondly, by means of his titles and the letters
which he received, to show the reputation he obtained
in consequence of his discoveries and thirdly, as far as
possible by means of his own letters, to give a picture
of the character which he made and kept during the time
of his great success.
On August 29, 18 31 , Faraday began his ' E lectrical
Researches.'
that as voltaic electricity powerfully affects a magnet,
so the magnet ought to exert a reaction upon the.
electric current. Guided by this idea, he made an ex-
periment, of which one part (the passage of a magnet
through a metallic helix connected with
a
galvanometer),
if separated from the rest of the experiment, would then
have made the great discovery of magneto-electricity.
VOL, II . E
S I T o .
In November 1825, also, he had failed to discover
voltaic induction. He passed a current through one
wire,
communicated with a galvanometer, and found ' no
result.' The mom entary existence of the phenomena
of induction then escaped him.
Again, December 2, 1825 , and April 22 , 1828, he
made experiments which gave ' no result.' These ex-
periments were not published.
production of electricity from magnetism.' His first
experiment, detailed in the second paragraph, records
the discovery by which he will be for ever known.
' I have had an iron ring made (soft iron ), iron
round and ^ths of an inch
thick, and ring six inches in
external diameter. Wound
one half of the coils being
separated by twine and ca-
lico ; there were three lengths
of wire, each about twenty-
four feet long, and they could
be connected as one length,
or used as separate lengths. By trials with a trough
each was insulated from the other. Will call this side
of the ring A. On the other side, but separated by
an interval, was wound wire in two pieces, together
amounting to about sixty feet in length, the direction
being as with the former coils. This side call B.
THE FIRST PERIOD OF HIS EXPERIMENTAL RESEARCHES.
' Charged a battery of ten pairs of plates four inches 1831.
square. Made the coil on B side one coil, and con- ^ 3 9
nected its extremities by a copper wire passing to a
distance, and just over a magnetic needle (three feet
from wire ring), then connected the ends of one of the
pieces on A side with battery : immediately a sensible
effect on needle. It oscillated and settled at last in
original position. On breaking connection of A side with
battery, again a disturbance of the needle.'
In the 17th paragraph, written on the 30th of August,
he says, ' May not these transient effects be connected
with causes of difference between power of metals at
rest and in motion in Arago's experiments ? '
After this he prepared fresh apparatus. W riting to
his friend E. Phillips, September 23 , he says, ' I am
busy just now again on electro-magnetism, and think I
have got hold of a good thing, bu t can't say. It may
be a weed instead of a fish that, after all my labour, I
may at last pull up.'
September 24 was the third day of his experiments.
He began paragraph 21 by trying to find the effect of
one helix of wire, carrying the voltaic current of ten
pairs of plates, upon another wire connected with a gal-
vanometer. 'N o induction sensible.' Paragraph 22.
Longer and different metallic helices showed no effect,
so he gave up those experiments for that day, and tried
the effect of bar magnets instead of the ring magnet he
had used on the first day.
In paragraph 33 he says, ' An iron cylinder had a
helix wound on it. The ends of the wires of the helix
were connected with the indicating helix at a distance
by copper wire. Then the iron placed between the poles
of bar magnets as in accompanying figure. Every time
JET. 4 0 .
the magnetic contact at x or s was made or broken, there
was magnetic motion at the indicating helix—the effect
being, as in former cases, not permanent, but a mere
momentary push or pull. But if the
electric communication (i.e. by the copper
wire) was broken, then the disjunction and
contacts produced no effect whatever.
Hence here distinct conversion of mag-
netism into electricity.'
Paragraphs 36, 37, and 38 describe the
discovery of induced voltaic currents.
' 36. A battery of ten troughs, each of
ten pairs of plates four inches square,
charged with good mixture of sulphuric
and nitric acid, and the following experiments made
with it in the following order.
' 37. One of the coils (of a helix of copper wire 203
feet long) was connected with the flat helix, and the
other (coil of same length round same block of wood)
with the poles of the battery (it having been found
that there was no metallic contact between the tw o);
the magnetic needle at the indicating flat helix was
affected, but so little as to be hardly sensible.
' 38. In place of the indicating helix, our galvano-
meter was used, and then a sudden jerk was perceived
Avhen the battery communication was
made
and
broken,
but it was so slight as to be scarcely visible. I t was
one way when made, the other when broken, and the
needle took up its natural position at intermediate
times.
' Hence there is an inducing effect without the pre-
sence of iron, bu t it is either very weak or else so
sudden as not to have time to move the needle,
rather suspect it is the latter.'
The fifth day of experiment was October 17. Pa-
ragraph 57 describes the discovery of the production
of electricity by the approximation of a magnet to a
wire.
' A cylindrical bar magnet three-quarters of an inch in
diameter, and eight inches and a half in length, had one
end just inserted into the end of the helix cylinder
(220 feet long) ; then it was quickly thrust in the whole
length, and the galvanometer needle moved ; then
pulled out, and again the
needle
opposite direction. This effect was repeated every time
the magnet was put in or out, and therefore a wave of
electricity was so produced from mere approximation
of a
in situ.''
The ninth day of his experiments was October 28,
and this day he ' made a copper disc turn round be-
tween the poles of the great horse-shoe magnet of the
Eoyal Society. The axis and edge of the disc were
connected with a galvanometer. The needle moved as
the disc turned.' The next day that he made experi-
ments, November 4, he found ' that a copper wire one-
eighth of an inch drawn between the poles and con-
ductors produced the effect.' In his paper, when
describing the experiment, he speaks of the metal
cutting the magnetic curves, and in a note to his
paper he says, ' By magnetic curves I mean lines
of magnetic forces which would be depicted by iron
filings.'
This is the germ of those ' lines of force ' which
rose up in the mind of Faraday into ' physical' and
almost tangible matte r. The influence which they had
upon his thoughts and experiments will be seen from
this time up to the date of the last researches which he
sent to the Eoyal Society in 1860.
In ten days of experiment these splendid results
were obtained. He collected the facts into the first series
of' Experimental Eesearches in Electricity.' It was read,
November 24th, at the Koyal Society. Then he went
to Brighton, and from thence, November 29th, he sends
an abstract of this paper in a letter to his friend E.
Phillips.
' Brighton : November 29, 1831.
' Dear Phillips,—For once in my life I am able to
sit down and write to you without feeling that my time
is so little that my letter must of necessity be a short
one ; and accordingly I have taken an extra large sheet
of paper, intending to fill it with news. And yet, as
to news, I have none, for I withdraw more and
more from society, and all I have to say is about
myself.
able ? And how does Mrs. Phillips do ; and the girls ?
Bad correspondent as I am, I think you owe me a
letter ; and as in the course of half an hour you will be
doubly in my debt, pray write us, and let us know all
about you. Mrs. Faraday wishes me not to forget to
put her kind remembrances to you and Mrs. Phillips
in my letter.
1
1
The day of election of the new Council of the Royal Society.
LETTERS DURING TH E FIRST PERIOD OF H IS RESEARCHES.
out of the Council, and care little for the rest, although 1831.
I should, as a matter of curiosity, have liked to see the
"JE^TO
Duke in the chair on such an occasion.
' W e are here to refresh. I have been working and
writing a paper tha t always knocks me up in health,
but now I feel well again, and able to pursue my
subject; and now I will tell you what it is about. The
title will be, I think, " Experimental Researches in
Electricity:
"—I.
I I . On the Evolution of Electricity from Magnetism ;
III . On a new Electrical Condition of Matter ; IV . On
Arago's Magnetic Phenom ena. There is a bill of fare
for you ; and, what is more, I hope it will not disappoint
you. Now the pith of all this I must give you very
briefly ; the demonstrations you shall have in the paper
when printed.
' I. W hen an electric current is passed through one
of two parallel wires, it causes at first a current in the
same direction through the other, but this induced
current does not last a moment, notwithstanding the
inducing current (from the voltaic battery) is continued ;
all seems unchanged, except that the principal current
continues its course. But when the curren t is stopped,
then a return current occurs in the wire under induc-
tion, of about the same intensity and momentary dura-
tion, but in the opposite direction to that first formed
Electricity in currents therefore exerts an inductive
action like ordinary electricity, but subject to peculiar
laws.
when the induction is established ; a reverse current
when the induction ceases, and a
peculiar state
in the
interim. Common electricity probably does the same
thing; but as it is at present impossible to separate the
LIFE OF FARADAY.
beginning and the end of a spark or discharge from each
other, all the effects are simultaneous and neutralise
each other.
' I I . Then I found that magnets would induce just
like voltaic currents, and by bringing helices and wires
and jackets up to the poles of magnets, electrical cur-
rents were produced in them ; these currents being
able to deflect the galvanometer, or to make, by means
of the helix, magnetic needles, or in one case even to
give a spark. Hence the evolution of electricity from
magnetism. The currents were not permanent. They
ceased the moment the wires ceased to approach the
magnet, because the new and apparently quiescent
state was assumed, just as in the case of the induction
of currents. But when the magnet was removed, and
its induction therefore ceased, the return currents ap-
peared as before. These two kinds of induction I have
distinguished by the terms
electric induction. Their identity of action and results
is, I think, a very powerful proof of M. Ampere's the-
ory of magnetism.
by induction between the beginning and end of the
inducing current gives rise to some very curious results.
I t explains why chemical action or other results of
electricity have never been as yet obtained in trials
with the magnet. In fact, the currents have no sensible
duration. I believe it will explain perfectly the trans-
ference of element; between the poles of the pile in
decomposition. But this part of the subject I have
reserved until the present experiments are completed ;
and it is so analogous, in some of its effects, to those of
Bitters secondary piles, De la Eive and Van Reek's
LETTERS DURING THE FIRST PERIOD OF H IS RESEARCHES.
peculiar properties of the poles of a voltaic pile, that I 1831.
should not wonder if they all proved ultimately to "li^to
depend on this state. The condition of matter I have
dignified by the term
Electrotonic, THE ELECTROTONIC
STATE. W hat do you think of that ? Am I not a bold
man, ignorant as I am, to coin words ? but I have con-
sulted the scholars. And now for IV.
' IV. The new state has enabled me to make out and
explain all Arago's phenomena of the rotating magnet or
copper plate, I believe, perfectly ; but as great names
are concerned (Arago, Babbage, Herschel, &c), and as
I have to differ from them, I have spoken with that
modesty which you so well know you and I and John
Frost' have in common, and for which the world so
justly commends us. I am even half afraid to tell you
what it is. You will think I am hoaxing you, or else in
your compassion you may conclude I am deceiving
myself. However, you need do neither, but had better
laugh, as I did most heartily when I found that it was
neither attraction nor repulsion, but just one of my
old
rotations
all the actions, which are very curious; but in con-
sequence of the electrotonic state being assumed and
lost as the parts of the plate whirl under the pole, and
in consequence of magneto-electric induction, currents
of electricity are formed in the direction of the radii;
continuing, for simple reasons, as long as the motion
continues, but ceasing when that ceases. Hence the
wonder is explained that the metal has powers on the
mao-net when moving, but not when at rest. Hence is
also explained the effect which Arago observed, and
1
A pushing acquaintance, wh o, with ou t claim of any kind, got himself
presented at Court.
1801. -which made him contradict Babbage and Herschel, and
ÊT. 4OT
say the power was repulsive ; bu t, as a whole, it is
really tangential. I t is quite comfortable to me to find
that experiment need not quail before mathematics, but
is quite competent to rival it in discovery ; and I am
amazed to find that what the high mathematicians have
announced as the essential condition to the rotation—
namely, that
instead of being required—i.e. if the currents could be
formed before the magnet came over the place instead
of
after
Phillips.
fully,
' M.
FARADAY.'
On December 5, 18 31 , Faraday was again at work
in continuation of his researches.
For three days he at first occupied himself with more
precise observations on the directions of the induced
curren ts; and on December 14, paragraph 217, he
' tried the effects of terrestrial magnetism in evolving
electricity. Obtained beautiful results.'
' The helix had the soft iron cylinder (freed from mag-
netism by a full red heat and cooling slowly) put into
it, and it was then connected with the galvanometer
by wires eight feet long
;
and immediately the needle moved; inverted it again,
the needle moved back; and, by repeating the motion
with the oscillations of the needle, made the latter
vibrate 180°, or more.'
The same day he ' made Arago 's experiment with
1 1
the earth magnet, only no magnet used, but the plate 1831.
pu t horizontal and rotated. The effect at the needle irTTu
was slight, but very distinct.'
Paragraph 227 .— 'Hence Arago's plate, a new elec-
trical machine.' On four other days of December he
experimented on terrestrial magneto-electric induction,
and on voltaic electric induction.
In January he experimented on the currents produced
by the earth's rotation—on the 10th at the lake in the
gardens of Kensington Palace, and on the 12th and
13th at Waterloo Bridge.
at Woolwich, experimented with magnet,
1
spark myself. Connected
general ends, and then
way that a blow at
a b
Then bringing
a b
1
The great magnet of the Royal Society was at thia time at Mr. Christie's.
Mr. Daniell's magnet. Am algamation of wires very
needful. This is a natu ral loadstone, and perhaps the
first used for the spark.'
These, and many other experiments which he made
in December and January, he sent to the Eoyal Society,
and his paper on terrestrial magneto-electric induction,
and on the force and direction of magneto-electric
induction generally, was read as the Bakerian lecture,
January 12, 1832.
densation of this second paper :—
' He placed a bar of iron in a coil of wire, and lifting
the bar into the direction of the dipping needle, he ex-
cited by this action a current in the coil. On reversing
the bar, a current in the opposite direction rushed
through the wire. The same effect was produced, when,
on holding the helix in the line of dip, a bar of iron was
thrust into it. Here, however, the earth acted on the
coil through the intermediation of the bar of iron. He
abandoned the bar, and simply set a copper-plate spin-
ning in a horizontal pla ne ; he knew that the earth's
lines of magnetic force then crossed the plate at an
angle of about 70°. W hen the plate spun round, the
lines of force were intersected and induced currents
generated, which produced their proper effect when
carried from the plate to the galvanometer. " W hen the
plate was in the magnetic meridian, or in any other
plane coinciding with the magnetic dip, then its rotation
produced no effect upon the galvanometer."
' At the suggestion of a mind fruitful in suggestions of
rotating iron disc. Both of them had found that when
in rotation the body exercised a peculiar action upon the
magnetic needle, deflecting it in a manner which was
not observed during quiescence; but neither of them was
aware at the time of the agent which produced this ex-
traordinary deflection. They ascribed it to some change
in the magnetism of the iron shell and disc.
' But Faraday at once saw that his induced currents
must come into play here, and he immediately obtained
them from an iron disc. W ith a hollow brass ball,
moreover, he produced the effects obtained by Mr.
Barlow. Iron was in no way necessary : the only con-
dition of success was that the rotating body should be
of a character to admit of the formation of currents in
its substance : it must, in other words, be a conductor
of electricity. The higher the conducting power, the
more copious were the curren ts. He now passes from
his little brass globe to the globe of the earth. He
plays like a magician with the earth's magnetism. He
sees the invisible lines along which its magnetic action
is exerted, and, sweeping his wand across these lines, he
evokes this new power. Placing a simple loop of wire
round a magnetic needle, he bends its upper portion to
the west: the north pole of the needle immediately
swerves to the ea st : he bends his loop to the east, and
the north pole moves to the west. Suspending a common
bar magnet in a vertical position, he causes it to spin
round its own axis. Its pole being connected with one
end of a galvanometer wire, and its equator with the
from the rotating magnet. H e remarks upon the "
sin-
gular
the magnet which carries it. The steel behaves as if
it were isolated from its own magnetism.
' And then his thoughts suddenly widen, and he asks
himself whether the rotating earth does not generate
induced currents as it turns round its axis from west to
east. In his experiment with the twirling magnet the
galvanometer wire remained at rest; one portion of
the circuit was in motion relatively to
another
portion.
But in the case of the twirling planet the galvanometer
wire would necessarily be carried along with the earth ;
there would be no relative motion. W hat must be the
consequence ? Take the case of a telegraph wire with
its two terminal plates dipped into the earth, and sup-
pose the wire to lie in the m agnetic meridian. The
ground underneath the wire is influenced, like the wire
itself, by the earth's rotation ; if a current from south to
north be generated in the wire, a similar curren t from
south to north would be generated in the earth under
the w ire : these currents would run against the same
terminal plate, and thus neutralise each other.
' This inference appears inevitable, bu t his profound
vision perceived its possible invalidity. He saw that it
was at least possible that the difference of conducting
power between the earth and the wire might give one
an advantage over the other, and that thus a residual or
differential curren t might be obtained. He combined
wires of different materials, and caused them to act in
opposition to each other, but found the combination
ineffectual. The more copious flow in the b et ter con-
ductor was exactly counterbalanced by the resistance of
THE FIRST PERIOD OF HIS EXPERIMENTAL RESEARCHES. 1 5
the worst. Still, though experiment was thus emphatic, 1831.
he would clear his mind of all discomfort by operating ÊT.39-+O.
on the earth itself. He went to the round lake near
Kensington Palace, and stretched 480 feet of copper
wire, north and south, over the lake, causing plates
soldered to the wire at its ends to dip into the water.
The copper wire was severed at the middle, and the
severed ends connected with a galvanometer. No effect
whatever was observed. But though quiescent water
gave no effect, moving water might. He therefore
worked at Waterloo Bridge for three days, during the
ebb and flow of the tide, but without any satisfactory
result. Still he urges, " Theoretically it seems a neces-
sary consequence, that where water is flowing there
electric currents should be formed. If a line be
imagined passing from Dover to Calais through the sea
and returning through the land, beneath the water, to
Dover, it traces out a circuit of conducting matter, one
part of which, when the water moves up or down the
channel, is cutting the magnetic curves of the earth,
whilst the other is relatively at rest. . . . There
is
every
reason to believe that currents do run in the general
direction of the circuit described, either one way or the
other, according as the passage of the waters is up or
down the Channel." This was written before the sub-
marine cable was thought of, and he once informed me
that actual observation upon that cable had been found
to be in accordance with his theoretic deduction.'
In addition to this noble work, which placed him
among the first philosophers, other work was done.
Dr. Tyndall says :—
class of Optical Deceptions," to which I believe the beau-
1-sMi. tiful optical toy called the chromatrope owes its origin.
JET.39-40.
In the same year he published a paper in the " Philoso-
phical Transactions," " On Vibrating Surfaces," in which
he solved an acoustical problem which, though of ex-
treme simplicity when
many eminent men. The problem was to account for
the fact that light bodies, such as the seed of lycopo-
dium, collected at the vibrating parts of sounding plates,
while sand ran to the nodal lines. Faraday showed
that the light bodies were entangled in the little whirl-
winds formed in the air over the places of vibration,
and through which the heavier sand was readily pro-
jected.'
Journal,' ' On the Limits of Vaporisation.' After Easter
he gave four afternoon lectures on optical deceptions,
lithography, flowing sand, and caoutchouc ; and during
the season he took five Friday evenings for his dis-
courses. One of these was on oxalam ide, lately dis-
covered by M. Dumas. His notes run thus :— ' Is an
artificial substance, yet approaching to organic matter.
Wood distilled, acid—isinglass distilled, alk ali ; hence
the interest. Not one to think that by ba ttery and
retort we may make mind and body, but still feel
free to observe effects, as far as we can trace them.'
The other lectures were on a peculiar class of optical de-
ceptions ; on light and phosphorescence ; on Trevelyan's
recent experiments, on the production of sound during
the conduction of heat; and on the arrangements as-
sumed by particles upon vibrating elastic surfaces.
II.
The only title he received this year was that of
honorary member of the Imperial Academy of Sciences,
St. Petersburg.
terpretation was given to his words, appears in a letter
which he wrote to M. Gray-Lussac, regarding the first
and second series of ' Experim ental Researches.' The
circumstances were these :—
the Eoyal Society, he wrote a ' short' and ' hasty ' and
' unfortunate ' letter to M. H achette, who communi-
cated it a week afterwards to the Academy of Sciences,
Paris,
account was printed in 'L e Temps.' M. Nobili saw
this, and, with M. Antinori, he immediately ' considered
the subject was given to the philosophical world for
general pursu it.' Their results were dated January 31 ,
1832, and they were published in the ' Antologia,'
which was dated November 1831. Of this Faraday
said, ' The circumstance of back date has caused many
here who have heard of Nobili's experiments by report
only, to imagine his results were anterior to, instead of
being dependent upon mine.'
March 1832. In the 'Philosophical Magazine ' for
June 1832, Faraday published a translation of Nobili's
VOL. II . C
Ê T . 3 9 - 4 0 .
first memoir, with notes, and later in the year he
wrote a long letter to M. Gay-Lussac, on Nobili and
Antinori's errors in magneto-electric induction. In
this letter he says, ' These philosophers unfortunately
had no other knowledge of my researches than the
short letter which I w rote to M. Hachette, and not
being careful to refer to my papers (though it appears
to me they should have done so, under the circum-
stances), they have mistaken altogether the sense of
a phrase relating to the beautiful observations of M.
Arago; they have presumed that I had not previously
done that which they thought they had done them-
selves ; and finally, they advance what appears to me
to be erroneous ideas of magneto-electric currents,
and give their ideas as corrections of mine, which had
not as yet come under their eyes.
'F irs t, let me rectify tha t which I consider as the
most serious error, the misinterpretation given to my
words ; for those committed in the experiments would
have been easily removed in the course of time.
'M . Nobili says: " H e (Faraday) then (ten years
ago) recognised, as the notice says, that by the rotation
of a metallic disc, under the influence of a magnet, we
may produce electric currents in the direction of the
radii of the disc, in sufficient quantity to make this
disc become a new electric machine." Now I never said
tha t which is here imputed to me. I said " the extra-
ordinary effect discovered by M. Arago was connected
in its nature with the electro-magnetic rotation, which
I had discovered several years before." I never said,
and never had-the intention of saying, that I "had dis-
covered that which M. Arago discovered." I have the
most earnest desire to have this error removed, for I
have always admired the prudence and philosophic 1831.
reserve shown by M. Arago, in resisting the temptation "ih^toT'
to give a theory of the effect he had discovered, so
long as he could not devise one which was perfect in
its application, and in refusing his assent to the im-
perfect theories of others.'
" W e have recently verified, extended, and perhaps
rectified in some parts, the results of the English phi-
losopher." W ith the greatest desire to be corrected
when in error, it is still impossible for me to discover
in the writings of these gentlemen any correction by
which I can profit/ And then at great length he
examines and compares their results with his own, and
concludes thus:—
' I cannot terminate this letter without again express-
ing the regret I feel in having been obliged to write it.
But if it be remembered that the memoirs of the
Italian philosophers were written and published
after
peared in the same number of the " Annales de Chimie
et de Physique " with mine ; and that, consequently,
they have the ripjyearance of carrying science beyond
that which I had myself done; that both their papers
accuse me of errors in experiment and theory, and,
beyond that, of good faith; that the last of these
writings bears the date of March, and has not been
followed by any correction or retractation on the part
of the authors, though we are now in December ; and
that I sent them, several months ago, copies of my
original papers, and also copies of notes on a transla-
tion of their first paper ; and if it be remembered that,
FAR ADA Y.
1832-34. after all, I have none of those e rror s to answ er for
AJô3l3. with which they reproach me, and that the memoirs of
these gentlemen are so worded, that I was constrained
to reply to the objections they ma de against m e ; I
hope that no person will say that I have been too
hasty to write that which migh t have been avoide d;
or that I should have shown my respect for the truth,
or rend ered justice to my own writings, and this branch
of science, if, knowing of such important errors, I had
not pointed them out.
' M. FARADAY.'
the vast amount, and the high importance of the
w ork which F ara da y did. Bu t the y show very little
of the reputation which he gained, and still less of his
nature.
I
It will be well to divide his work into that which he
did for the Eo yal S ocie ty; that which he did for the
Eoyal Institution; and that which he published else-
where.
The th ird series of ' Ex per im en tal Eesearc hes in Elec-
tricity ' was on the identity of electricities derived from
different sources, and on the relation by measure of
common and voltaic electricity.
soon proved that ordinary (frictional) electricity affects
the galvanometer.
A ugu st 30th , 31st, Septem ber 1st and 3rd, he
worked on the chemical decompositions pro duced by
the common frictional electrical curren t. On the latter 1832.
day he writes in his note-book, ' As identity of common IEVTL^
and voltaic electricity is proved, we may reason from
the former, when intense, as to the manner of action of
the latter.'
tion, which ultimately formed part of the fifth series
of researches; and as early as September 8 he made
an experiment on chemical decomposition without any
poles.
sion : ' The number of Leyden jars (8 and 15) charged,
measured the tension and the number of turns of the
plate machine, the quantity of the electricity.'
He then made a standard voltaic arrangement of
platina and zinc wire
V h of an inch in diameter, and
a standard acid of one drop of sulphuric acid in four
ounces of w ater ; and then he compares the voltaic
action with the action of the plate machine on the
galvanometer. And September 15 he works on chemi-
cal decomposition, and ends thus : ' Hence it would
appear that both in magnetic deflection and in chemical
effect the curren t of the standard voltaic battery for
eiavht beats of the watch was equal to the electricity of
thirty turns of the machine, and that therefore common
and voltaic electricity are alike in all respects.'
The paper in which his own facts and all he could
collect elsewhere on the subject are contained, was sent
to theEoyal Society December 15, and was read on the
10th and 17th of January. At the conclusion he says,
' The extension which the present investigations have
enabled me to make, of the facts and views constitu-
ting the theory of electro-chemical decomposition, will,
1832. with some other points of electrical doctrine, be almost
^ E T T T
series of these researches.
of the relation by measure of common and voltaic elec-
tricity must be mentioned here :—
' After he had proved to his own satisfaction the
identity of electricities, he tried to compare them
quantitatively together. The terms quantity and in-
tensity, which Faraday constantly used, need a word of
explanation here. He might charge a single Leyden
jar by twenty turns of his machine, or he might charge
a battery of ten jars by the same number of turns.
The quantity in both cases would be sensibly the same,
but the
for here the electricity would be less diffused. Faraday
first satisfied himself that the needle of his galvano-
meter was caused to swing through the same arc by
the same quantity of machine electricity, whether it
was condensed in a small ba ttery or diffused over a
large one. Thus the electricity developed by thirty
turns of his machine produced, under very variable con-
ditions of ba ttery surface, the same deflection. Hence
he inferred the possibility of comparing, as regards
quantity, electricities which differ greatly from each
other in intensity.
electricity. Moistening bibulous paper with the iodide
of potassium—a favourite test of his—and subjecting
it to the action of machine electricity, he decomposed
the iodide, find formed a brown spot where the iodine
was liberated. Then he immersed two wires, one of
zinc,
the other of platinum, each ^ t h of an 'inch in
THE FIRST PERIOD OP HIS EXPERIMENTAL RESEARCHES. 2 3
diameter, to a depth of fth s of an inch in acidulated
water during eight beats of his watch, or -^th s of a
second ; and found that the needle of his galvanometer
swung through the same arc, and coloured his moistened
paper to the same extent, as thirty turns of his large
electrical machine. Twenty-eight turns of the machine
produced an effect distinctly less than that produced
by his two wires. Now, the quantity of water decom-
posed by the wires in this experiment totally eluded
observation
a quantity of electric force which, if applied in a
proper form, would kill a rat, and no man would like
to bear it.
tity of electricity associated with the particles or atoms
of matter," he endeavours to give an idea of the amount
of electrical force involved in the decomposition of a
single grain of water. He is almost afraid to mention
it, for he estimates it at 800,000 discharges of his large
Leyden battery . This, if concentrated in a single dis-
charge, would be equal to a very great flash of light-
ning ; while the chemical action of a single grain of
water on four grains of zinc would yield electricity
equal in quantity to a powerful thunderstorm. Thus
his mind rises from the minute to the vast, expand-
ing involuntarily from the smallest laboratory fact till
it embraces the largest and grandest natural pheno-
mena.'
The fourth series of researches was on a new law of
electric conduction and on conducting power generally.
It was received at the Koyal Society April 24.
December 24th, 1832, Faraday says in his note-
1833. book, ' Can an electric current, voltaic or not, decom-
~"i£17T pose a solid body—ice, &c. ? If it cannot, wha t would
frozen gum, lac, wax, &c. ? '
January 23, 1833, he begins his experiments on ice.
The ice was not quite dry, and so the needle was de-
flected. On the 24th he says, ' Made some excellent
experiments on ice—quite d ry ; at 10°, or perhaps
under; not the slightest deflection of the needle oc-
curred .' On the 26th, ' If ice will not conduct, is it
because it cannot decompose
His paper begins thus :—' I was working with ice,
when I was suddenly stopped by finding that ice was a
non-conductor of electricity.'
'"Franklin's Experiments on Electricity," 4to, 5th edi-
tion, 1774, p. 36 : " A dry cake of ice or an icicle
held between two (persons) in a circle likewise prevents
the shock, which one would not expect, as water con-
ducts it so perfectly well." '
February 14th he began to experiment ' on sub-
stances solid at common temperatures, but fusible, and
of such composition as was presumed would supply the
place of or act like water.'
Next he took nitre : ' Whilst nitre was solid it did not
conduct, i.e. no current passed through it affecting the
galvanometer ; on melting the nitre, and then putting
the negative pole on the galvanometer, the needle was
knocked round, as if the metals had touched through
the nitre, and strong decomposing action took place.
On allowing temperature to fall, the moment nitre
solidified, the current through it ceased, yet negative
wire was actually imbedded and cemented in the nitre '
' Hence,' he says, ' nitre is exactly like water
:
whilst
solid it is a non-conductor, and when fluid a conductor 1833.
and decomposed
distinction, or action, or any exclusive power, in voltaic
chemical decomposition.
general assumption of insulating powers, so soon as
fluid matter becomes solid, a new point, before un-
suspected, and very extraordinary. Seems to confer a
new property on the matter in the second state. Curious
that as gas and as solid non-conduct, and that as liquid
conduct.'
with the conducting power of carbon, and non-con-
ducting power of diamond.'
tion by voltaic pile is due to slight power superadded
upon previous chemical attractive forces of particles
when fluid ? Since mere fixation of particles prevents,
it must be slight.'
power ? As if here the electricity were only a transfer
of a series of alternations or vibrations, and not a body
transm itted directly. May settle or relate to question
of materiality or fluid of electricity.'
On February 21 he experimented first with sulphuret
of silver. ' Very
' When all was cold, conducted a little (by the galva-
nometer).
conducting
power in-
creased (a curious fac t); yet I do not think it became
hio'h enough to
fuse the sulphuret.
The whole passed
whilst in the solid state. The hot sulphuret seems to
conduct as a metal would, and could get sparks with
2G LIFE OP FARADAY.
wires at the end, and a fine spark with charcoal.' And
then he proceeds to examine a multitude of other sub-
stances.
when solid, and wire freezed in, non-conductor. When
fused, conducted very well, and was decomposed. At
P. pole much action and gas, Chlorine (?). A t K pole
magnesium separated and no gas. Sometimes magne-
sium burn t, flying off in globules, burning brilliantly.
When wire at that pole put in water or dilute muriatic
acid, matter round it acted powerfully, evolving hy-
drogen and forming magnesia; and when wire and
surrounding matter held in spirit lamp, magnesium
burnt with intense light into magnesia.
VERY
GOOD
EXPERIMENT.'
April 1st, he returns to the sulphuret of silver again.
' All the effects of electro-chemical decomposition seem
to show that in ordinary chemical affinity the particles
exert an influence not merely on those with which they
are combined, but also, although to a weaker extent,
upon those particles combined with their neighbours:
that, in fact, it is not a mere tendency to unite par-
ticle to particle, but that tendency is general, and that
even those in excess exert an influence, though it be
not enough to overpower definite combination. Many
facts in chemistry also bear on this view, that particles
act in common. Berthollet, Phillips, & c , have quoted
cases,
nomena. Electro-chemical decomposition seems to be
essentially dependent upon it.'
April 5th, he still worked on the sulphuret of
silver, and says : ' Hence it is quite clear that a solid
can conduct, that it can decompose whilst solid, that
increasing heat
inents are electro-chemically arranged, that sulphur is
*lsZTC
April 13th .— ' W hy did Davy require water in de-
composing potassa
the attraction of the poles being stronger than that of
the particles separated, it would follow that the weakest
electrical attraction was stronger than the strongest, or
than very strong, chemical attraction; i.e. such as exists
between oxygen and hydrogen, acid and alkali, potas-
sium and oxygen, chlorine and sodium, &c. This not
likely.'
' If voltaic decomposition of the kind I believe, then
revise all substances upon the new view, to see if they
may not be decomposed, &c.'
' A single element is never attracted by a pole,
i.e. without attraction of other element at other pole.
Hence doubt Mr. Brande's experiments on attraction
of gases and vapours. Doubt attraction by poles alto-
gether.'
though the current passed through water, it did not pass
through ice ; why not, since they are one and the same
substance ? Some years subsequently he answered this
question by saying that the liquid condition enables
the molecule of water to turn round so as to place itself
in the proper line of polarisation, while the rigidity of
the solid condition prevents this arrangem ent. This
polar arrangement must precede decomposition, and
decomposition is an accompaniment of conduction. He
then passed on to other substances; to oxides and
1833.
'^T.Î. ' found them all insulators when solid, and conductors
when fused. In all cases, moreover, except one—and
this exception he thought might be apparent o n l y -
he found the passage of the current across the fused
compound to be accompanied by its decomposition.
Is then the act of decomposition essential to the act
of conduction in these bodies? Even recently this
question was warmly contested. Faraday was very
cautious latterly in expressing himself upon this subject;
but as a matter of fact he held that an infinitesimal
quantity of electricity might pass through a compound
liquid without producing its decomposition. De la Eive,
who has been a great worker on the chemical phe-
nomena of the pile, is very emphatic on the other side.
Experiment, according to him and others, establishes
in the most conclusive manner that no trace of elec-
tricity can pass through a liquid compound without
producing its equivalent decomposition.'
tion ; new conditions of electro-chemical decomposition,
influence of water in electro-chemical decomposition,
and theory of electro-chemical decomposition. It was
received at the Eoyal Society Ju ne 18 . This series
is continued in the seventh series on electro-chemical
decomposition (continued), and is so connected with the
eighth series on the electricity of the voltaic pile, that
these three papers must be considered as one vast
work. In the two first, Faraday tries to make clear to
himself what actually takes place in solutions through
which currents of electricity are passing, and in the
third paper he applies the facts he had obtained,
and proves that they hold good in the voltaic pile.
Having satisfied himself of the identity of the differ- 1833.
ent electricities, and of their difference only in intensity, "i^ TiT
he thought it probable that the most intense would,
when applied to chemical decomposition, give new
facts and new views. In April he passes the machine
electricity through pieces of litmus and turmeric mois-
tened and connected by solution of sulphate of soda.
Wherever the current entered or left the test paper,
there was evidence of decom position,' indicating at once
an internal action of the parts suffering decomposition,
and appearing to show that the power that is effectual
in separating the elements is exerted there and not in
the poles.'
in 1845 . He begins, 'A s to effect of decomposing
solution on polarised ray of light. It can be only two
directions, one across the current, the other along it.'
' Have been passing ray of polarised light through de-
composing solutions to ascertain if any sensible effect
on the light.'
the electric current.
or substances will be found to have (as a consequence
of decomposition or arrangement for the time) any
effect on the polarised ray.'
' Should now try non-decomposing bodies, as solid
nitre,
nitrate of silver, borax, glass, &c, whilst solid, to
1833.
see if any internal state induced, which by decom-
I E ^ I T ' position is destroyed, i.e. whether, when they cannot
decompose, any state of electrical tension is present.
My borate of lead glass good, and common electricity
better than voltaic'
May 6 he makes further experiments, and concludes,
' Hence I see no reason to expect that any kind of
structure or tension can be rendered evident, either in
decomposing or non-decomposing bodies, in insulating
or conducting states.'
tion.
And May 16 he writes, 'I s the law this? "E qu al
currents of electricity measured by the galvanometer
evolve equal volumes of gas or effect equal chemical
actions in a constant medium ? " Is it possible it may
generalise so far as to give equal chemical action,
estimated on the same elements on variable media
?
Ought it not to be so if decomposition essential to
conduction ?' And then he proceeds to experiment with
different sized poles, different decomposing solutions,
and different kinds of poles, including water as a pole.
In his paper he sums up his conclusion as to the
nature of electro-chemical decomposition thus : ' It
appears to me that the effect is produced by an internal
corpuscular action, exerted according to the direction
of the electric current, and that it is due to a force
either superadded to or giving direction to the ordinary
chemical affinity of the bodies present. The body
under decomposition may be considered as a mass of
acting particles, all those which are included in the
course of the electric current contributing to the final
effect.'
;
The poles are merely the surfaces or doors by 1833.
which the electricity enters into or passes out of the JET^42^
substances suffering decomposition. They limit the
extent of that substance in the course of the electric
current, being its
series gives a far clearer view than can be gathered
from the notes of the experiments. This research
lasted all the autumn of 1833.
Dr. Tyndall says, ' His paper on electro-chemical
decomposition, received by the Eoyal Society January 9,
1834,
He would avoid the word " current " if he could. He
does abandon the word " poles " as applied to the ends
of a decomposing cell, because it suggests the idea of
attraction, substituting for it the perfectly neutral term
electrodes. He applied the term electrolyte to every
substance which can be decomposed by the current,
and the act of decomposition lie calls electrolysis. All
these terms have become current in science. He called
the positive electrode the anode, and the negative one
the cathode, but these terms, though frequently used,
have not enjoyed the same currency as the others.
The terms union and cation, which he applied to the
constituents of the decomposed electrolyte, and the
term
ion,
still less frequently employed.
and seeks to supply himself with a measure of voltaic
electricity. This he finds in the quantity of water
decomposed by the current. He tests this measure in
3 2 LIFE OF FARADAY.
1832-34. all possible ways, to assure himself that no error can
i:i.4'o-43. arise from its employment. He places in the course of
one and the same current a series of cells with elec-
trodes of different sizes, some of them plates of plati-
num, others merely platinum wires, and collects the
gas liberated on each distinct pair of electrodes. He
finds the quantity of gas to be the same for all. Thus
he concludes that when the same quantity of electricity
is caused to pass through a series of cells containing
acidulated water, the electro-chemical action is inde-
pendent of the size of the electrodes. He next proves
that variations in intensity do not interfere with this
equality of action. W hether his battery is charged
with strong acid or with weak ; whether it consists of
five pairs or of fifty pairs ; in short, whatever be its
source, when the same current is sent through his series
of cells, the same amount of decomposition takes place
in all. He next assures himself tha t the strength or
weakness of his dilute acid does not interfere with this
law. Sending the same curren t through a series of
cells containing mixtures of sulphuric acid and water
of different strengths, he finds, however the proportion
of acid to water might vary, the same amount of gas
to be collected in all the cells. A crowd of facts of
this character forced upon Faraday's mind the conclu-
sion that the amount of electro-chemical decomposition
depends, not upon the size of the electrodes, not upon
the intensity of the current, not upon the strength of
the solution, but solely upon the quantity of electricity
which passes through the cell. The quantity of elec-
tricity he concludes is proportional to the amount of
chemical action. On this law Faraday based the con-
struction of his celebrated voltameter or measurer of
voltaic cluctriritv.
' But before he can apply this measure he must clear 1832-34.
his ground of numerous possible sources of error. The
decomposition of his acidulated water is certainly a
direct result of the cu rren t; but as the varied and
important researches of MM. Becquerel, De la Eive,
and others had shown, there are also
secondary
actions,
pure action of the current. These actions may occur
in two ways : either the liberated
ion
the electrode against which it is set free, forming a
chemical compound with tha t electrode ; or it may
seize upon the substance of the electrolyte itself, and
thus introduce into the circuit chemical actions over
and above those due to the current. Faraday sub-
jected these secondary actions to an exhaustive exami-
nation. Instructed by his experiments, and rendered
competent by them to distinguish between primary
and secondary results, he proceeds to establish the
doctrine of " definite electro-chemical decomposition."
' Into the same circuit he introduced his voltameter,
which consisted of a graduated tube filled with acidu-
lated water and provided with platinum plates for the
decomposition of the water, and also a cell containing
chloride of tin. Experiments already referred to had
taught him that this substance, though an insulator
when solid, is a conductor when fused, the passage of
the current being always accompanied by the decom-
position of the chloride. He wished now to ascertain
what relation this decomposition bore to that of the
water in his voltameter.
continue until " a reasonable quantity of gas " was col-
lected in the voltameter. The circuit was then broken,
VOL. II . D
1SW-34. and the quantity of tin liberated compared with the
S M
quantity of gas". The weight of the former was 3-2
grains, that of the latter 04 9742 of a grain. Oxygen,
as you know, unites with hydrogen in the proportion
of 8 to 1 to form water. Calling the equivalent, or, as
it is sometimes called, the atomic weight of hydrogen
1,
that of oxygen is 8 ; that of water is consequently
8 -f
in Faraday's experiment be represented by the number
9, or in other words by the equivalent of water, then
the quantity of tin liberated from the fused chloride is
found by an easy calculation to be 57 '9, which is almost
exactly the chemical equivalent of tin. Thus both
the water and the chloride were broken up in propor-
tions expressed by their respective equivalents. The
amount of electric force which wrenched asunder the
constituents of the molecule of water was competent,
and neither more nor less than competent, to wrench
asunder the constituents of the molecules of the chlo-
ride of tin. The fact is typical. W ith the indica-
tions of his voltameter he compared the decomposition
of other substances both singly and in series. He sub-
mitted his conclusions to numberless tests. He pur-
posely introduced secondary actions. He endeavoured
to hamper the fulfilment of those laws which it was the
intense desire of his mind to see established. But from
all these difficulties emerged the golden truth , that
under every variety of circumstances the decompositions
of the voltaic current are as definite in their character
as those chemical combinations which yave birth to
the atomic theory. This law of electro-chemical de-
composition ranks, in point of importance, w ith that
of definite combining proportions in chemistry.'
One note from his laboratory book and one from 1833-34.
his paper may be added. AÂI^S.
December 18th, 1833, he writes : ' The present voltaic
apparatus, i.e. the trough, must be a very coarse, wasteful
arrangement if referred to its first principle. For the
zinc dissolved
rightly collected, to affect the world almost.'
In his paper he says
:
'Zinc and platina wires one-
eighteenth of an inch in diameter and about half an inch
long dipped into dilute sulphuric acid so weak that it
is not sensibly sour to the tongue, or scarcely to our
most delicate test-papers, will evolve more electricity
in one-twentieth of a minute than any man would
willingly allow to pass through his body at once. The
chemical action of a grain of water upon four grains
of zinc can evolve electricity equal in quantity to that
of a powerful thunderstorm.'
chemical equivalents—propositions relating to,' after
considering the possibility of making a table of real
electro-chemical equivalents, he continues, ' I must
keep my researches really
hypothetical
imaginations.'
In the early part of 1834 Faraday was at work on the
quantity of electricity evolved, and on secondary actions,
and among other substances he used fluoride of lead.
From this he worked for fluorine. On February 10th
he writes
my views of the elementary experiment of a single pair
of metals, and the relation to poles, &c, &c, and if it
had not occurred to me whether he might work at it.
I told him my views, and wished him to work con-
D
3 6 LIFE OF FABADAT.
1833-34. tem poran eous ly with m e. H e behaved very gen erou sly,
JET.41-43. leaving it open to me alone. B ut if ano ther c atches m y
idea, and works it out before I can write my paper, I
shall always reg ret tha t Daniell has given w ay to m e,
and tha t ano ther should come before him . M ust leave
iluorine, and hasten this matter of the
VOLTAIC PILE.
He then proceeds, on February 12th, to experiments
on the ge nerating plates and the intensity of the curren t
they produce. First he uses am algam ated plates, and
then he puts intervening platina plates ; and he writes,
' how very needful th e cu rrent is
to decomposition
the cases whe re the intervening platiuas are used. But
they cannot be cause and effect to each oth er . W hat is
the common origin and cause of both ? Must make this
out. It is of no use con tinuing to suppose one as pro-
ducing the other in either order.'
' These cases of retardation seem beautifully to show
the antagonism of the chemical powers at the elec-
tro-motive par ts with the chemical pow ers a t the in-
terposed parts . Th e first are prod uc ing elec tric effects,
the second opposing electric effects, and the two seem
equipoised as in a balance, and in both cause and effect
appear to be identical with each othe r. H en ce chem i-
cal action merely electrical action, an d electric action
merely chemical.'
Almost imm ediately he ad d s: ' I am continually
wanting a clear, definite view of the actions in a
single voltaic circuit.' Th en again, after some fur-
ther experimen ts on resistance, he sa y s: 'M us t con-
sider the case of single decom position v ery we ll and
closely, for tha t includes the wh ole. W h y is it ne-
cessary there should be a discharge of electricity before
action can go on ? W hy no t zinc alone decom pose, and 1833-34.
how is it that in existing circumstances the platina MTUI^
helps ? '
On Feb rua ry 1 9th he m akes the experim ent, to show
that contac t of the single pair of metals is not necessary
to produce chemical decomposition.
On the 22nd he writes : 'W e seem to have the power
of deciding in certain cases of chemical affinity (as of
zinc with the oxygen of water, & c ), which of two modes
of action of the one power shall be exe rted. In the
one mode we can transfer the pow er on it, being able
to produce elsewhere its equivalent of action; in
the other it is not transferred on, bu t ex erted at th e
spot. Th e first is the case of voltaic-e lectric pr o-
duction, the other the ordinary cases of chemical
affinity. But bo th are chemical actions, and due to one
power or princip le. Th at no electricity is set free in
the latter case shows the equality of forces, and
therefore of electricity in those quantities which are
called chemical equivalents. Hence anothe r proof
that chemical affinity and electricity are the same.'
H e co ntin ues: ' I must very closely consider and
exam ine a case of' com bination in which no electric
cu rrent is pro duced, such as zinc in dilute sulphu ric
acid, or oxide of lead in nitric acid, &c. W ha t becomes
he re of all the electricity which must pass du ring the
com bination ? How is it destroyed between the par -
ticles ? Of course they are able to neutralise each other,
but how do they neutralise
?
' Are not rubbed glass and the rubber exactly in the
state of zinc and the oxygen of wa ter in an electro-
motive circle? i.e. when the rub bed glass and the
rubber are separated, are they not in the state assumed
1833-34. by the zinc and the oxygen before they combine,
JET.41-43.
and before the contact is made in a single voltaic
circle ? They probably give an exalted view of the
conditions of the particles of the zinc and oxygen—
a permanent view, as it were. How do the states
agree ?
not proceeding to a full effect; in the voltaic circle
being completed and being followed in succession by a
multitude of others of the same kind? In th e last it is
the attraction of the zinc for the oxygen of the oxide,
and this would tell as well for the instances of induc-
tion, and perhaps of common electricity.'
He then experiments on the intensity of a current
and its power of affecting decompositions in different
resisting fluids; and March 8th writes
:
believe that the current passes, but the intensity is not
sufficient
Faraday published these and other experiments in
the eighth series of his 'Researches.' It was received
at the Royal Society, April 7, 1834. I t was on the
electricity of the voltaic pile : its source, quantity, in-
tensity. In this and the two former papers Faraday
worked ' to remove doubtful know ledge ' regarding the
definite action of electricity on decomposing bodies, and
the identity of the power so used with the power to be
overcome. He got clear ideas of the absence of all
attractive power in the poles; clear ideas of the active
state of each particle of the electroleids between the
eisode and exode
of
chemical action caused by a definite quantity of electri-
39
city, and clear ideas that the contact of metals was not 1833-34.
the origin of the electro-motive force, but that volta- JETAI-43.
electric excitation and ordinary chemical affinity are
' both chemical actions and due to one force or
principle.'
At the end of this paper he says: ' I would rather
defer revising the whole theory of electro-chemical
decomposition until I can obtain clearer views of the
way in which the power tinder consideration can appear
at one time as associated with particles giving them
their chemical attraction, and at another as free elec-
tricity.'
ber 30, 1833. This paper arose from a fact observed
in the course of one of the experiments, mentioned
in the seventh series of ' Researches.' It furnishes
the clearest picture of the way in which Faraday
worked.
' Have been comparing decomposition of muriatic acid
Mwritctic A£Ld,
and water together, as to the equivalents of elements
evolved by a given current of electricity.' ' I re-
marked that whilst b tube was being examined, the
a had
a
MÂU^3. alone, and by battery evolved gas until it was full.
Being left to
this gas gradually went or di-
minished, and after th ree o r four hou rs, not a fourth
pa rt was left. At first, twelve o'clock, th ere were 11(5
parts , and a t last, five o'clock, the re were only 1 3 5
parts.
Th ink this must have been an effect of per-
meability through the cork at top, by wires, & c , but
must examine it closely, and also use tube hermetically
sealed at the top.'
'September 18th.—To-day examined the 135 parts
left ye ste rday ; by heating spongy platin a in it the
gas diminished to two parts . H enc e, think it cannot
be due to permeability of cork,
&c,
for no sensible
portion of air has entered. Think it must be due to
recombination of the oxygen and hyd rogen in some
way.'
On 19th , after making more sure of his facts, he
writes : ' I suspect all this is some com bining power,
possessed by the platina of the poles— perhaps given
to it during the decomposition.' ' M ust ascertain
wh ether bo th poles, or only the positive has the power.'
' If poles have this pow er, the effect will imm ediately
connect with that of spongy platina, and probably
explain it.' ' Pe rhaps m erely digesting platina in dilute
sulphuric acid, or at least in nitro-m uriatic acid, may
give it this pow er.' ' Probab ly heating in air, or in
flame with little muriate of ammonia vapour, or in
chlorine, &c., will give this pow er to platin a, in p late
or lump. Prob ably also heat much assist it Try all
this.' ' '
J
Almost imm ediately afterwards he w ri te s: ' It is
quite clear that the positive pole has peculiar power of
causing oxygen and hydrogen to combine.' And then 1833-34.
he left the subject till October 10, when he found that
positive pole, put into mixed gases,
became
part, and the rest of the gas exploded.
' A pole, or, as it should now be called, a plate, was
merely heated by the spirit-lamp and blow-pipe, not
having been connected with the battery, and put up
into gas, oxygen and hydrogen. At first, there was no
action, but after a while, condensation began and went
on well at the last.'
October 11 he says : ' Hence heat can bring platina
into the acting state.' And then he tries mechanical
and chemical actions to prepare the platinum plate.
On October 14 he writes
:
the sulphuric acid, the surfaces (of plates) acquired
such a state as to cause much friction when the pieces
were rubbed against each other. This no doubt
because of their perfectly clean state, and helps to
show that effect is due to that clean state of surfaces
which acid and battery induce.' Then he found that
by heating an active plate it sometimes lost its power,
and he writes : ' Must remember that platina can
combine with carbon by heat, and that probably the
surface is thus affected in these modes of igniiing.'
This day he cleaned a platinum plate chemically
with potass, hea t, sulphuric acid and water, and then
put it into the mixed gases. ' Instant excellent action ;
the gas rose quickly, the platinum became red-hot, and
Doberiner's effect was produced without action of battery
on the platina—Good.'
November 7, he tries the effect of gold and palla-
dium, silver, copper. The two first acted.
November 8 and 12, tried the effect of mixing
1833-34. other gases with the oxygen and hydrogen, and hydro-
-ST.41-43. g en a lo n e .
Then he experimented on the rapidity with which
substances get dirty.
ficial actions of matter, and the actions of particles not
directly or strongly in combination, are becoming daily
more and more important in chemical as well as in
mechanical philosophy.'
The conclusion at which he arrived is thus stated in
his paper :—
press upon my mind the conviction, that the effects in
question are entirely incidental, and of a secondary
nature (not electrical, as M. Doberiner, the discoverer
of the action of spongy platinum, had considered),
that they are dependent upon the
natural
attractive force possessed by many bodies, especially
those which are solid, in an eminent degree, and pro-
bably belonging to all; by which they are drawn into
association more or less close, without at the same
time undergoing chemical combination, though often
assuming the condition of adhesion; and which occa-
sionally leads, under favourable circumstances, as in
the present instance, to the combination of bodies
simultaneously subjected to this attraction.'
In the abstract of the Friday evening discourse
which he gave on this subject in 1834, he writes:
'
totally different from chemical affinity; and second, by
the peculiar condition of elastic bodies when mixed.
The first supposition he attempted to support thus : he
threw a little magnesia on water, and at the same
time filings of zinc on a different portion of water.
The former immediately became
latter remained dry and floated; in fact, it seemed to
evince, as it were, a repulsive power towards the water.
In
the
me-
the only difference is that the matters adhering to the
surface have been in the latter case removed; but they
are chiefly gases, vapours, atmospheric air, &c. ; for
such, therefore, metals must have a specific power of
attraction, and, being thus in contact with them, refuse
contact with liquid bodies. For the second point,
Dalton
has
duces liquefaction) the same relative distance; but it
appears that they may approach indefinitely near to
the
particles
a
clean
me-
of approximation, is at the same moment brought into
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Bence Jones, Michael Faraday the Life and Letter Volume 2