History Pot Clock Book Printing

8/6/2019 History Pot Clock Book Printing

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History

Earliest known ceramics are the Gravettian figurines that date to 29,000 to 25,000 BC

Cupisnique pottery. Stirrup spout bottlewith a feline-human representation. Larco MuseumCollection. Lima-Peru
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An Incipient Jmonpottery vessel reconstructed from fragments (10,000-8,000 BCE), TokyoNational Museum,Japan

It is believed that the earliest pottery wares were hand built and fired in bonfires. Firing timeswere short but the peak-temperatures achieved in thefirecould be high, perhaps in the region of

900 C, and were reached very quickly. Clays tempered with sand, grit, crushed shell or crushedpottery were often used to make bonfire-fired ceramics, because they provided an open bodytexture that allows water and other volatile components of the clay to escape freely. The coarserparticles in the clay also acted to restrain shrinkage within the bodies of the wares duringcooling, which was carried out slowly to reduce the risk of thermal stress and cracking. In themain, early bonfire-fired wares were made with rounded bottoms, to avoid sharp angles thatmight be susceptible to cracking. The earliest intentionally constructed kilns werepit-kilnsortrench-kilns; holes dug in the ground and covered with fuel. Holes in the ground providedinsulation and resulted in better control over firing.

The earliest known ceramic objects areGravettianfigurines such as those discovered at DolniVestonice in the modern-day Czech Republic. The Venus of Doln Vstonice (Vstonick

Venue in Czech) is a Venus figurine, a statuette of a nude female figure dated to 29,00025,000BCE (Gravettian industry).[22] The earliest pottery vessel found to date was excavated from theYuchanyan Cavein southern China and theProceedings of the National Academy of Sciencesin2009 reports that the ware dates back to 18,000 years ago.[23]Pottery vessels made by theIncipient Jmon people of Japan from around 10,500 BCE have also been found.[24][25] The term"Jmon" means "cord-marked" in Japanese. This refers to the markings made on clay vessels andfigures using sticks with cords wrapped around them. Pottery which dates back to 10,000 BCEhave also been excavated in China.[26]It appears that pottery was independently developed inNorth Africa during the tenth millennium b.p.[27] and in South America during the seventhmillennium b.p.[28] In several cultures, the earliest vessels were made either by hand-shaping, orby rolling the clay into a thin round cord which was then coiled round on itself to form thevessel.

The earliest history of pottery production can be divided into 4 periods namely; the Hassunaperiod (5000 - 4500 BCE), the Halaf period (4500 - 4000 BCE), the Ubaid period (4000 - 3000BCE), and the Uruk period (3500 - 2000 BCE). The invention of thepotter's wheel inMesopotamiasometime between 6000 and 4000 BCE (Ubaid period) revolutionized potteryproduction. Specialized potters were then able to meet the expanding needs of the world's firstcities. Pottery was in use in ancient India during theMehrgarh Period II (5500 - 4800 BCE) andMerhgarh Period III (4800 - 3500 BCE), known as the ceramic Neolithic and chalcolithic.
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Pottery, including items known as the ed-Dur vessels, originated in regions of the Indus valleyand has been found in a number of sites in theIndus valley civilization.[29][30]

In the Mediterranean, during theGreek Dark Ages (1100800 BCE), artists used geometricdesigns such as squares, circles and lines to decorate amphoras and other pottery. The periodbetween 1500-300 BCE in ancient Korea is known as the Mumun Pottery Period.[31]

The quality of pottery has varied historically, in part dependent upon the repute in which thepotter's craft was held by the community.[citation needed] For example, in the Chalcolithic period inMesopotamia, Halafian pottery achieved a level of technical competence and sophistication, notseen until the later developments ofGreek potterywith Corinthian and Attic ware.[citation needed] Thedistinctive Red Samian ware of the Early Roman Empirewas copied by regional pottersthroughout the Empire. The Dark Ageperiod saw a collapse in the quality of European potterywhich did not recover in status and quality until the European Renaissance.[citation needed]
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Pottery is dishes, plates, cups, and cooking pots made out ofclay. It is a good idea to makedishes and pots out of clay for several reasons. Clay is cheap and easy to get,pretty muchanybody can make a useful pot out of it, and you can make it waterproof pretty easily too. Plus itcan be made very beautiful, if you know what you are doing. And it is easy to make yours lookdifferent from your neighbor's.People first started making pottery out of clay around 6000BC, near the beginning of theNeolithic period. Before that most people had been nomadic, and pottery is too heavy and toobreakable for people who are going to move around a lot. Probably they had always known how,but just hadn't done it much, the same asplanting seeds. In the beginning, pottery was made byjust pushing a hole into a ball of clay, or by making a long snake of clay and coiling it up into apot shape. Many early pots, meant to be used once and thrown away, are nothing more than alarge lump of clay that someone socked their fist into, the way you might sock your fist into acatcher's mitt. These were just lightly fired in a fire of dry weeds. The coiled kind of pot wasoften fired in a hotter fire, probably by being put in an open campfire or bonfire.

By around 3000BC, at the beginning of the Bronze Age, people had begun to use the slowpotter's wheel. This is a little platform made of wood that you build the pot on; you can turn itaround so that instead of having to walk around your pot you can sit still and turn the pot around.In the hands of someone who is good at using it, it does make potting a lot faster.

A woman in Mexico digging clay and using a slow wheel to make a pot.

But by 2000BC, the slow wheel had been almost entirely replaced in Europe and Asia by thefast wheel, which is also a platform, but one which spins on an axle, like a top. You can start itspinning with a push or a kick, and then draw the pot gradually out of the lump of clay. Using thefast wheel, a good potter can make a pot every minute or so, and all of them almost exactly thesame. It's much faster than coiling or the slow wheel, and so pots got much cheaper than they

had been before. The Indo-Europeans, migrating at this time intoGreece and Italy and China,brought the idea of the fast wheel with them.

From the beginning, people used pottery as a way of constructing theirsocial identity, orshowing who they were and how they were different from other people. Many of the designsused on pottery were borrowed from cloth, which was also used to identify people of one groupor another. Greekpottery is very different from West Asian pottery of the same time, and both ofthem are different from Egyptian pottery, orChinese pottery.Etruscan potteryis different too,but similar to Greek pottery in many ways.
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The beginning of the Roman Empiresaw some big technological and economic changes in theWestern pottery industry. First, people began painting pottery red instead of black. Then they

began making it in molds instead of painting it. Around the same time, the Phoenicians inventedglass-blowing, and this made glass cheap enough to be a serious competitor with pottery. Peoplepretty much stopped making pottery cups, and everyone drank out of glasses. Even a lot ofbowls, and little things like perfume containers, were made out of glass.Also, by about 100AD, most of the nicer pottery used in the Roman Empire was made inNorthAfrica and shipped by boat all over the Empire, using the sea and the rivers.

The Arab invasionof North Africa around 700 AD ended the North African pottery trade, andafter that pottery was locally made again for some time in the West, and not very good. The nextgreat developments in pottery were not in the West but in Sui Dynasty China, where pottersbegan to make porcelain (PORR-se-lenn) cups and pitchers around 700 AD. This gleaming whitepottery was popular not only in China but in West Asiatoo. But it was very expensive in West

Asia, because it had to be carried all the way from China ondonkeys and camels. So the WestAsian potters invented lead glazes, which made ordinary pots look white and shiny. This made akind of imitation porcelain which was a lot cheaper.

A little later on, European andChinese potters began using lead glazes too. About 1200 AD,potters of the Yuan dynasty in China began to use different color glazes to create designs on theirpots. Chinese pottery was still the best and the most expensive. So West Asian potters also usedthese colored glazes to imitate Chinese designs, and Europeans used colored glazes to imitate theWest Asian designs.
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The pottery of ancient India is one of the most tangible and iconic elements of ancient Indianart. Pottery has also been found in the early settlements ofMehrgarh.

Contents[hide] 1 Vedic pottery

2 History

3 Indus Valley civilization

4 Styles

4.1 Unglazed pottery

4.2 Glazed pottery

4.3 Terracotta

4.4 Papier-mache

5 Process of pottery making

6 Recovery of ancient pottery

7 Notes

8 Further reading

[edit] Vedic potteryWilhelm Rau(1900) has examined the references topotteryin Vedic texts like the BlackYajurVedaand the Taittiriya Samhita. According to his study, Vedic pottery is for example hand-made

and unpainted. According to Kuzmina (1983), Vedic pottery that matches Willhelm's Raudescription cannot be found in Asia Minor and Central Asia, though the pottery of Andronovo issimilar in some respects.[1].

[edit] HistoryThe tradition of pottery-making in India is very old. The ancient pottery of a country tells a lotabout its civilization. For thousands of years pottery has been an important form of expression.Pottery is claimed[by whom?] to be the most sensual of all arts. India has a great tradition of potterymaking. The real beginning of Indian pottery began with the Indus Valley Civilization. There isproof of pottery being constructed in two ways, handmade and wheel-made. There are more thana million potters in India. These potters are claimed to be wonderful masters of their trade.[2]

[edit] Indus Valley civilizationJean-Franois Jarrigehas noted that there is a continuity between pottery of third millenniumBaluchistan and second millennium Pirak.[3]

[edit] Styles
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Over time India's simple style of molding clay went into an evolution. A number of distinctstyles emerged from this simple style. Some of the most popular forms of pottery includeunglazed pottery, glazed pottery, terracotta, and papier-mache.[4].

[edit] Unglazed pottery

This is the oldest form of pottery practiced in India. There are three types of unglazed pottery.First is paper thin pottery, biscuit-colored pottery decorated with incised patterns. Next is thescrafito technique; the pot is polished and painted with red and white slips along with intricatepatterns. The third is polished pottery; this type of pottery is strong and deeply incised, and hasstylized patterns of arabesques.[5].

[edit] Glazed pottery

This era of pottery began in the 12th century AD. This type of pottery contains a whitebackground and has blue and green patterns. Glazed pottery is only practiced in selected regionsof the country.[6]

[edit] Terracotta

A style of pottery wherein women prepare clay figures to propitiate their gods and goddesses,during festivals. In Moela deities are created with molded clay on a flat surface. They are thenfired and painted in bright colors. Other parts of India use this style to make figures like horseswith riders, and other votives.[7].

[edit] Papier-mache

This type of pottery is made from paper pulp, which is coarsely mashed and mixed with coppersulphate and rice-flour paste. It is then shaped by covering the mould with a thin paper and thenapplying layers of the mixture. The designers then sketch designs on them and polish the potterywith bright colors. A touch of gold is always found on papier-mache products. The goldrepresents its roots to the Persian design.[8].

[edit] Process of pottery makingStep One: First you[who?] need to obtain and prepare the clay. Once the clay is dug up it is thenstored in a dry place. The clay is prepared by adding water to obtain a moistened, sticky texture.[9].

Step Two: The clay is passed through a machine called a pug mill. This improves the consistencyand texture of the clay. Traditionally the process was called dancing the clay .[10].

Dancing The Clay: The clay is thrown on the ground and red sand is added to it. The men thenwould walk up and down the clay mixing the sand and clay with their feet. This was done untilthe clay had a smooth and elastic consistency.[11].

Step Three: (Wedging The Clay) The clay is kneaded by hand on a board and then rolled into aball.[12].

Step Four: (Throwing A Pot) This term is used for molding the clay into pottery on the potter'swheel. The clay is centered on the wheel and the potter works the clay vertically up and downwith their hands. Some pots are made directly on the wheel while others are made in parts of thewheel and then assembled afterwards.[13].
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Step Five: (Drying) Pots are then set aside to air dry. Some pots are placed in the shade onshelves while others are placed directly in the sun.[14].

Step Six: (Carving) Designs are now carved into the pottery or etched on the surface with anysharp pointy object or material that is available to them. The carving is done while the clay isonly leather dry. After the designs are made the pottery is then set aside to finish the drying

process.[15]

.Step Seven: (Baking) The pots are now baked/fired in a kiln or oven. This process can either bedone in an electrical oven or a traditional dirt oven. This process removes excess water from thepottery, and as a result the clay hardens. Baking also changes the color of the clay.[16].

[edit] Recovery of ancient potterySome of India's pottery has been recovered by divers from Nanhai Marine Archaeology as theyevacuate shipwrecks in the South China Sea. This sea was the main shipping route linking Chinato India from the 14th to the 19th century. When a shipwreck is found, the researchers recoverthe artifacts and document each piece. During this they also search for the old kilns where thepottery was once made. The national museum of Malaysia is given all the unique artifacts along

with thirty percent of all other recovered items. Nanhai Marine Archaeology is then permitted tosell their portion of the recovered artifacts in order to finance future projects.[17].
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ClockFrom Wikipedia, the free encyclopedia

Jump to: navigation, search

For other uses, see Clock (disambiguation).

Platform clock at King's Cross railway station, London.

A clockis an instrument used to indicate, keep, and co-ordinate time. The word clockis derivedultimately (via Dutch, Northern French, and Medieval Latin) from the Celtic words clagan andclocca meaning "bell". A silent instrument lacking such a mechanism has traditionally beenknown as a timepiece.[1] In general usage today a "clock" refers to any device for measuring anddisplaying the time. Watchesand other timepieces that can be carried on one's person are oftendistinguished from clocks.[2]
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Clock at the Royal Observatory, Greenwich

Replica of an ancient Chineseincense clock

The clock is one of the oldest human inventions, meeting the need to consistently measureintervals of time shorter than the natural units: the day; the lunar month; and the year. Devicesoperating on several different physical processes have been used over the millennia, culminatingin the clocks of today.
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Contents[hide]

1 Sundials and other devices

2 Water clocks

3 Early mechanical clocks

3.1 A new mechanism

3.2 Early astronomical clocks

4 Later developments

5 How clocks work

5.1 Power source

5.2 Oscillator

5.2.1 Synchronized or slave clocks

5.3 Controller

5.4 Counter chain

5.5 Indicator

6 Types

6.1 Time display methods

6.1.1 Analog clocks

6.1.2 Digital clocks

6.1.3 Auditory clocks

7 Purposes 7.1 Ideal clocks

7.2 Navigation

8 Seismology

9 Specific types of clocks

10 See also

10.1 Newsgroup

11 Notes

12 References

13 External links

[edit] Sundials and other devices

The sundial, which measures the time of day by using the sun, was widely used inancient times.A well-constructed sundial can measure local solar time with reasonable accuracy, and sundialscontinued to be used to monitor the performance of clocks until the modern era. However, its
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practical limitations - it requires the sun to shine and does not work at all during the night -encouraged the use of other techniques for measuring time.

Candle clocks, and sticks of incense that burn down at approximately predictable speeds havealso been used to estimate the passing of time. In anhourglass, fine sandpours through a tinyhole at a constant rate and indicates a predetermined passage of an arbitrary period of time.

[edit] Water clocks

Main article: Water clock

A scale model ofSu Song's Astronomical Clock Tower, built in 11th century Kaifeng,

China. It was driven by a large waterwheel, chain drive, and escapement

mechanism.

Water clocks, also known as clepsydrae (sg: clepsydra), along with the sundials, are possibly theoldest time-measuring instruments, with the only exceptions being the vertical gnomonand theday-counting tally stick.[3] Given their great antiquity, where and when they first existed are not

known and perhaps unknowable. The bowl-shaped outflow is the simplest form of a water clockand is known to have existed in Babylon and inEgyptaround the 16th century BC. Other regionsof the world, including India and China, also have early evidence of water clocks, but the earliestdates are less certain. Some authors, however, write about water clocks appearing as early as4000 BC in these regions of the world. [4]

Greekastronomer, Andronicus of Cyrrhus, supervised the construction of the Tower of theWinds in Athens in the 1st century B.C.[5]
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The Greekand Roman civilizations are credited for initially advancing water clock design toinclude complex gearing,[6] which was connected to fanciful automata and also resulted inimproved accuracy. These advances were passed on through Byzantium and Islamictimes,eventually making their way to Europe. Independently, the Chinese developed their ownadvanced water clocksin 725 A.D., passing their ideas on to Korea and Japan.

Automatic clock ofal-Jazari, 12th century.

Some water clock designs were developed independently and some knowledge was transferred

through the spread of trade. Pre-modern societies do not have the same precise timekeepingrequirements that exist in modern industrial societies, where every hour of work or rest ismonitored, and work may start or finish at any time regardless of external conditions. Instead,water clocks in ancient societies were used mainly forastrologicalreasons. These early waterclocks were calibrated with a sundial. While never reaching the level of accuracy of a moderntimepiece, the water clock was the most accurate and commonly used timekeeping device formillennia, until it was replaced by the more accuratependulum clockin 17th century Europe.

In 797 (or possibly 801), the Abbasidcaliph ofBaghdad,Harun al-Rashid, presentedCharlemagne with anAsian Elephantnamed Abul-Abbas together with a "particularly elaborateexample" of a water[7] clock.
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An elephant clock in a manuscript by Al-Jazari (1206 AD) from The Book ofKnowledge of Ingenious Mechanical Devices.[8]

In the 13th century, Al-Jazari, an engineer who worked forArtuqid king of Diyar-Bakr,Nasir al-Din, made numerous clocks of all shapes and sizes. The book described 50 mechanical devicesin 6 categories, including water clocks. The most reputed clocks includedthe Elephant, ScribeandCastle clocks, all of which have been successfully reconstructed. As well as telling the time,

these grand clocks were symbols of status, grandeur and wealth of the Urtuq State.[citation needed]

[edit] Early mechanical clocks

None of the first clocks survive from 13th century Europe, but various mentions in churchrecords reveal some of the early history of the clock.

The word horologia (from the Greek, hour, and , to tell) was used to describe allthese devices, but the use of this word (still used in several Romance languages) for alltimekeepers conceals from us the true nature of the mechanisms. For example, there is a recordthat in 1176 Sens Cathedral installed a horologe[citation needed] but the mechanism used is unknown.According to Jocelin of Brakelond, in 1198 during a fire at the abbey of St Edmundsbury (nowBury St Edmunds), the monks 'ran to the clock' to fetch water, indicating that their water clock

had a reservoir large enough to help extinguish the occasional fire.[9]

[edit] A new mechanism

The word clock(from the Latin word clocca, "bell"), which gradually supersedes "horologe",suggests that it was the sound of bells which also characterized the prototype mechanical clocksthat appeared during the 13th century in Europe.
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Outside of Europe, the escapement mechanism had been known and used in medieval China, asthe Song Dynastyhorologist and engineerSu Song (10201101) incorporated it into hisastronomical clock-tower ofKaifeng in 1088.[10] However, his astronomical clock and rotatingarmillary spherestill relied on the use of flowing water (i.e. hydraulics), while Europeanclockworks of the following centuries shed this old habit for a more efficient driving power ofweights, in addition to the escapement mechanism.

A mercury clock, described in theLibros del saber, a Spanish work from AD 1277 consisting oftranslations and paraphrases of Arabic works, is sometimes quoted as evidence for Muslimknowledge of a mechanical clock. The first mercury powered automata clock was invented byIbn Khalafa al-Muradi[11][12]

Between 1280 and 1320, there is an increase in the number of references to clocks and horologesin church records, and this probably indicates that a new type of clock mechanism had beendevised. Existing clock mechanisms that used water powerwere being adapted to take theirdriving power from falling weights. This power was controlled by some form of oscillatingmechanism, probably derived from existing bell-ringing or alarm devices. This controlled releaseof power - the escapement - marks the beginning of the true mechanical clock.

These mechanical clocks were intended for two main purposes: for signalling and notification(e.g. the timing of services and public events), and for modeling the solar system. The formerpurpose is administrative, the latter arises naturally given the scholarly interest in astronomy,science, astrology, and how these subjects integrated with the religious philosophy of the time.The astrolabe was used both by astronomers and astrologers, and it was natural to apply aclockwork drive to the rotating plate to produce a working model of the solar system.

Simple clocks intended mainly for notification were installed in towers, and did not alwaysrequire faces or hands. They would have announced thecanonical hoursor intervals between settimes of prayer. Canonical hours varied in length as the times of sunrise and sunset shifted. Themore sophisticated astronomical clocks would have had moving dials or hands, and would haveshown the time in various time systems, includingItalian hours, canonical hours, and time as

measured by astronomers at the time. Both styles of clock started acquiring extravagant featuressuch as automata.

In 1283, a large clock was installed at Dunstable Priory; its location above therood screensuggests that it was not a water clock[citation needed]. In 1292,Canterbury Cathedral installed a 'greathorloge'. Over the next 30 years there are brief mentions of clocks at a number of ecclesiasticalinstitutions in England, Italy, and France. In 1322, a new clock was installed in Norwich, anexpensive replacement for an earlier clock installed in 1273. This had a large (2 metre)astronomical dial with automata and bells. The costs of the installation included the full-timeemployment of two clockkeepers for two years[citation needed].
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[edit] Early astronomical clocks

Richard of Wallingford pointing to a clock, his gift to St Albans Abbey

Besides the Chinese astronomical clock of Su Song in 1088 mentioned above, in Europe therewere the clocks constructed by Richard of Wallingford in St Albans by 1336, and by Giovannide Dondi in Padua from 1348 to 1364. They no longer exist, but detailed descriptions of theirdesign and construction survive,[citation needed] and modern reproductions have been made. Theyillustrate how quickly the theory of the mechanical clock had been translated into practicalconstructions, and also that one of the many impulses to their development had been the desire ofastronomers to investigate celestial phenomena.

Wallingford's clock had a large astrolabe-type dial, showing the sun, the moon's age, phase, and

node, a star map, and possibly the planets. In addition, it had a wheel of fortune and an indicatorof the state of the tide at London Bridge. Bells rang every hour, the number of strokes indicatingthe time.

Dondi's clock was a seven-sided construction, 1 metre high, with dials showing the time of day,including minutes, the motions of all the known planets, an automatic calendar of fixed andmovable feasts, and an eclipse prediction hand rotating once every 18 years.

It is not known how accurate or reliable these clocks would have been. They were probablyadjusted manually every day to compensate for errors caused by wear and imprecisemanufacture.

Water clocks are sometimes still used today, and can be examined in places such as ancient

castles and museums.The Salisbury Cathedral clock, built in 1386, is considered to be the world's oldest survivingmechanical clock that strikes the hours.[13]

[edit] Later developments

Clockmakers developed their art in various ways. Building smaller clocks was a technicalchallenge, as was improving accuracy and reliability. Clocks could be impressive showpieces todemonstrate skilled craftsmanship, or less expensive, mass-produced items for domestic use. The
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escapement in particular was an important factor affecting the clock's accuracy, so manydifferent mechanisms were tried.

Spring-driven clocks appeared during the 15th century, [14][15][16] although they are oftenerroneously credited toNrnberg watchmakerPeter Henlein (or Henle, or Hele) around 1511.[17][18][19]The earliest existing spring driven clock is the chamber clock given to Peter the Good,

Duke of Burgundy, around 1430, now in the Germanisches Nationalmuseum.[15]

Spring powerpresented clockmakers with a new problem; how to keep the clockmovement running at aconstant rate as the spring ran down. This resulted in the invention of thestackfreedand thefuseein the 15th century, and many other innovations, down to the invention of the moderngoingbarrelin 1760.

Early clock dials did not use minutes and seconds. A clock with a dial indicating minutes wasillustrated in a 1475 manuscript by Paulus Almanus,[20] and some 15th-century clocks inGermany indicated minutes and seconds.[21] An early record of a second hand on a clock datesback to about 1560, on a clock now in the Fremersdorf collection.[citation needed] However, this clockcould not have been accurate, and the second hand was probably for indicating that the clock wasworking.

During the 15th and 16th centuries, clockmaking flourished, particularly in the metalworkingtowns ofNurembergand Augsburg, and in Blois, France. Some of the more basic table clockshave only one time-keeping hand, with the dial between the hour markers being divided into fourequal parts making the clocks readable to the nearest 15 minutes. Other clocks were exhibitionsof craftsmanship and skill, incorporating astronomical indicators and musical movements. Thecross-beat escapement was invented in 1584 by Jost Brgi, who also developed the remontoire.Brgi's clocks were a great improvement in accuracy as they were correct to within a minute aday.[22][23] These clocks helped the 16th-century astronomerTycho Brahe to observe astronomicalevents with much greater precision than before.

A mechanical weight-drivenastronomical clockwith a verge-and-foliot escapement, a strikingtrain of gears, an alarm, and a representation of the moon's phases was described by the Ottoman

engineerTaqi al-Din in his book, The Brightest Stars for the Construction of Mechanical Clocks(Al-Kawkib al-durriyya f wadh' al-bankmat al-dawriyya), published in 1556-1559.[24]

Similarly to earlier 15th-century European alarm clocks,[25][26] it was capable of sounding at aspecified time, achieved by placing a peg on the dial wheel. At the requested time, the pegactivated a ringing device. The clock had threedialswhich indicated hours, degrees and minutes.He later made an observational clock for the Istanbul observatory of Taqi al-Din (15771580),describing it as "a mechanical clock with three dials which show the hours, the minutes, and theseconds." This was an important innovation in 16th-century practical astronomy, as at the start ofthe century clocks were not accurate enough to be used for astronomical purposes.[27]
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French rococo bracket clocks, (Museum of Time, Besanon)

The next development in accuracy occurred after 1656 with the invention of thependulum clock.

Galileohad the idea to use a swinging bob to regulate the motion of a time telling device earlierin the 17th century. Christiaan Huygens, however, is usually credited as the inventor. Hedetermined the mathematical formula that related pendulum length to time (99.38 cm or39.13 inches for the one second movement) and had the first pendulum-driven clock made. In1670, the English clockmaker William Clement created theanchor escapement,[citation needed] animprovement over Huygens' crown escapement[citation needed]. Within just one generation, minutehands and then secondhands were added.

A major stimulus to improving the accuracy and reliability of clocks was the importance ofprecise time-keeping for navigation. The position of a ship at sea could be determined withreasonable accuracy if a navigator could refer to a clock that lost or gained less than about 10seconds per day. This clock could not contain a pendulum, which would be virtually useless on arocking ship. Many European governments offered a largeprize for anyone that could determinelongitude accurately; for example, Great Britain offered 20,000 pounds, equivalent to millions ofdollars today. The reward was eventually claimed in 1761 by John Harrison, who dedicated hislife to improving the accuracy of his clocks. His H5 clock was in error by less than 5 secondsover 10 weeks.[28]

The excitement over the pendulum clock had attracted the attention of designers resulting in aproliferation of clock forms. Notably, the longcase clock(also known as thegrandfather clock)was created to house the pendulum and works. The English clockmaker William Clement is alsocredited with developing this form in 1670 or 1671. It was also at this time that clock casesbegan to be made of wood and clock faces to utilize enamel as well as hand-painted ceramics.

French decimal clock from the time of the French Revolution

On November 17, 1797, Eli Terry received his firstpatentfor a clock. Terry is known as thefounder of the American clock-making industry.
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Alexander Bain, Scottish clockmaker, patented theelectric clockin 1840. The electric clock'smainspring is wound either with an electric motoror with an electro-magnetand armature. In1841, he first patented the electromagnetic pendulum.

The development ofelectronics in the 20th century led to clocks with no clockwork parts at all.Time in these cases is measured in several ways, such as by the vibration of a tuning fork, the

behaviour ofquartz crystals, or the quantum vibrations of atoms. Even mechanical clocks havesince come to be largely powered by batteries, removing the need for winding.
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List of subjects| Sources | Feedback HISTORY OF CLOCKS

Before AD 1200TimeSundial and water clockA tower clock in China

13th - 16th century16th - 18th centuryTo be completed

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Time

Time, a central theme in modern life, has for most ofhuman history been thought of in very imprecise terms.

The day and the week are easily recognized and recorded -though an accuratecalendarfor the year is hard to achieve.The forenoon is easily distinguishable from the afternoon,provided the sun is shining, and the position of the sun inthe landscape can reveal roughly how much of the day haspassed. By contrast the smaller parcels of time - hours,minutes and seconds - have until recent centuries been bothunmeasurable and unneeded.

Sundial and water clock: from the 2nd millennium BC

The movement of the sun through the sky makes possible asimple estimate of time, from the length and position of ashadow cast by a vertical stick. (It also makes possiblemore elaborate calculations, as in the attempt ofErathosthenes to measure the world - seeErathosthenes andthe camels). If marks are made where the sun's shadow
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falls, the time of day can be recorded in a consistentmanner.

The result is the sundial. An Egyptian example survivesfrom about 800 BC, but the principle is certainly familiar toastronomers very much earlier. However it is difficult tomeasure time precisely on a sundial, because the sun's paththroug the sky changes with the seasons. Early attempts atprecision in time-keeping rely on a different principle.

The water clock, known from a Greek word as theclepsydra, attempts to measure time by the amount of waterwhich drips from a tank. This would be a reliable form ofclock if the flow of water could be perfectly controlled. Inpractice it cannot. The clepsydra has an honourable historyfrom perhaps 1400 BC in Egypt, through Greece and Romeand the Arab civlizations and China, and even up to the

16th century in Europe. But it is more of a toy than atimepiece.

The hourglass, using sand on the same principle, has aneven longer career. It is a standard feature on 18th-centurypulpits in Britain, ensuring a sermon of sufficient length. Ina reduced form it can still be found timing an egg.

A tower clock in China: AD 1094

After six years' work, a Buddhist monk by the name of SuSong completes a great tower, some thirty feet high, whichis designed to reveal the movement of the stars and thehours of the day. Figures pop out of doors and strike bellsto signify the hours.

The power comes from a water wheel occupying the lowerpart of the tower. Su Song has designed a device whichstops the water wheel except for a brief spell, once everyquarter of an hour, when the weight of the water(accumulated in vessels on the rim) is sufficient to trip amechanism. The wheel, lurching forward, drives themachinery of the tower to the next stationary point in a

continuing cycle.

This device (which in Su Sung's tower must feel like aminor earthquake every time it slams the machinery intoaction) is an early example of an escapement - a conceptessential to mechanical clockwork. In any form of clockbased on machinery, power must be delivered to themechanism in intermittent bursts which can be precisely


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regulated. The rationing of power is the function of theescapement. The real birth of mechanical clockwork awaitsa reliable version, developed in Europe in the 13th century.

Meanwhile Su Sung's tower clock, ready for inspection bythe emperor in 1094, is destroyed shortly afterwards bymaraudingbarbarians from the north.

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13th - 16th century

Clockwork in EuropeDomestic clocks16th - 18th centuryTo be completed

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Clockwork in Europe: 13th - 14th century AD

Europe at the end of the Middle Ages is busy trying tocapture time. The underlying aim is as much astronomical(to reflect the movement of the heavenly bodies) as it is todo with the more mundane task of measuring everybody'sday. But the attraction of that achievement is recognizedtoo. A textbook on astronomy, written by 'Robert theEnglishman' in 1271, says that 'clockmakers are trying tomake a wheel which will make one complete revolution' ineach day, but that 'they cannot quite perfect their work'.

What prevents them even beginning to perfect their work isthe lack of an escapement. But a practical version of thisdates from only a few years later.

A working escapement is invented in about 1275. The
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process allows a toothed wheel to turn, one tooth at a time,by successive teeth catching against knobs projecting froman upright rod which oscillates back and forth. The speed ofits oscillation is regulated by a horizontal bar (known as afoliot) attached to the top of the rod. The time taken in thefoliot's swing can be regulated by moving weights in or outon each arm.

The function of the foliot is the same as that of thependulum in modern clocks, but it is less efficient in thatgravity is not helping it to oscillate. A very heavy weight isneeded to power the clock, involving massive machineryand much friction.

Nevertheless the foliot works to a degree acceptable at thetime (a clock in the Middle Ages is counted a goodtimekeeper if it loses or gains only a quarter of an hour a

day), and in the 14th century there are increasingly frequentreferences to clocks in European cities. A particularlyelaborate one is built between 1348 and 1364 in Padua byGiovanni de' Dondi, a professor of astronomy at theuniversity who writes a detailed description of his clock. A14th-century manuscript of his text has the earliestillustration of a clock mechanism with its escapement.

The world's three oldest surviving examples of clockworkdate from the last years of the 14th century.

The famous clock in Salisbury cathedral, installed by 1386and still working today with its original mechanism, is avery plain piece of machinery. It has no face, beingdesigned only to strike the hours. Striking is the mainfunction of all early clocks (the word has links with theFrench cloche, meaning 'bell').

In 1389 a great clock is installed above a bridge spanning astreet in Rouen. It remains one of the famous sights of thecity, though its glorious gilded dial is a later addition anditsfoliot has been replaced by a pendulum (in 1713). Thehistorical distinction of the Rouen clock is that it is the first

machine designed to strike the quarter-hours.

In 1392 the bishop of Wells instals a clock in his cathedral.The bishop has previously been in Salisbury, and the sameengineer seems to have made the new clock. It not onlystrikes the quarters. It steals a march on Rouen by having adial, showing the movement of astronomical bodies.


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With escapements, chiming mechanisms and dials, clocksare now set to evolve into their more familiar selves. Andthe telling of time soon alters people's perceptions of timeitself. Hours, minutes and seconds are units which onlycome into existence as the ability to measure themdevelops.

Domestic clocks: 15th century AD

After the success of the clocks in Europe's cathedrals in thelate 14th century, and the introduction of the clock face inplaces such as Wells, kings and nobles naturally want thisimpressive technology at home.

The first domestic clocks, in the early 15th century, areminiature versions of the cathedral clocks - powered byhanging weights, regulated by escapements with a foliot,

and showing the time to the great man's family andhousehold by means of a single hand working its wayround a 12-hour circuit on the clock's face. But before themiddle of the 15th century a development of greatsignificance occurs, in the form of a spring-drivenmechanism.

The earliest surviving spring-driven clock, now in theScience Museum in London, dates from about 1450. Bythat time clockmakers have not only discovered how totransmit power to the mechanism from a coiled spring.They have also devised a simple but effective solution tothe problem inherent in a coiled spring which steadily losespower as it uncoils.

The solution to this is the fusee.

The fusee is a cone, bearing a spiral of grooves on itssurface, which forms part of the axle driving the wheels ofthe clock mechanism. The length of gut linking the drum ofthe spring to the axle is wound round the fusee. It lies onthe thinnest part of the cone when the spring is fully woundand reaches its broadest circumference by the time the

spring is weak. Increased leverage exactly counteractsdecreasing strength.

These two devices, eliminating the need for weights, makepossible clocks which stand on tables, clocks which can betaken from room to room, even clocks to accompany atraveller in a carriage. Eventually, most significant of all,they make possible thepocket watch.
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Watches: 16th - 17th century AD

The first watches, made in Nuremberg from about 1500, are spherical metal objects, about threeinches in diameter, designed to hang on a ribbon round the neck. They derive from similar metalspheres used as pomanders, to hold aromatic herbs which will protect the wearer against diseaseor vile odours.

The first watchmakers place their somewhat primitive mechanism inside cases of this sort. Asingle hand set into a flat section at the base makes its way round a dial marked with the division

of twelve hours.

For their first century and more, watches are worn outside the clothes and are regarded more asjewels than as useful instruments (a comment also on their timekeeping abilities). The best ofthem are exquisitely decorated in enamel.

The spherical watch of this kind evolves in the late 17th century into the slimmer pocket watch,thanks largely to Christiaan Huygens. This distinguished Dutch physicist makes two importantcontributions to time-keeping - thependulum clockand the spiralbalance spring.

The pendulum clock: AD 1656-1657

Christiaan Huygens spends Christmas day, in the Hague in 1656, constructing a model of a clockon a new principle. The principle itself has been observed by Galileo, traditionally as a result ofwatching a lamp swing to and fro in the cathedral when he is a student in Pisa. Galileo laterproves experimentally that a swinging suspended object takes the same time to complete each


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swing regardless of how far it travels.

This consistency prompts Galileo to suggest that a pendulum might be useful in clocks. But noone has been able to apply that insight, until Huygens finds that his model works.

A craftsman in the Hague makes the first full-scale clock on this principle for Huygens in 1657.But it is in England that the idea is taken up with the greatest enthusiasm.

By 1600 London clockmakers have already developed the characteristic shape which makes bestuse of the new mechanism - that of the longcase clock, more affectionately known as thegrandfather clock.

The pocket watch: AD 1675

Nineteen years after making his model of the pendulum clock, Huygens invents a device of equalsignificance in the development of the watch. It is the spiral balance, also known as thehairspring (an invention also claimed, less convincingly, by Robert Hooke). This very finespring, coiled flat, controls the speed of oscillation of the balance wheel. For the first time it ispossible to make a watch which is reasonably accurate - and slim.

Both elements are important, for the sober gentlemen of the late 17th century are less inclinedthan their ancestors to wearjewels round the neck. A watch which will keep the time and slipinto a waistcoat pocket is what they require.


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Thomas Tompion, the greatest of English clock and watchmakers, is one of thefirst to apply the hairspring successfully in pocket watches (of which his workshop producesmore than 6000 in his lifetime). The new accuracy of these instruments prompts an addition tothe face of a watch - that of the minute hand.

The familiar watch face, with two concentric hands moving round a single dial, is at firstconsidered confusing. There are experiments with several other arrangements of the hour andminute hand, before the design which has since been taken for granted is widely accepted.

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History of Books

Origins and antiquityMain article: History of writing

Writing is a system oflinguisticsymbols which permit one to transmit and conserve information.Writing appears to have developed between the 7th millennium BC and the4th millennium BC,first in the form of early mnemonicsymbols which became a system ofideograms orpictographsthrough simplification. The oldest known forms of writing were thus primarilylogographic innature. Latersyllabic and alphabetic(or segmental) writing emerged.

Silk, in China, was also a base for writing. Writing was done with brushes. Many other materialswere used as bases: bone, bronze, pottery, shell, etc. In India, for example, dried palm tree leaveswere used; in Mesoamerica another type of plant, Amate. Any material which will hold andtransmit text is a candidate for use in bookmaking.

The book is also linked to the desire of humans to create lasting records. Stones could be themost ancient form of writing, but wood would be the first medium to take the guise of a book.The words biblos and liberfirst meant "fibre inside of a tree". InChinese, the characterthatmeans book is an image of a tablet ofbamboo. Wooden tablets (Rongorongo) were also made onEaster Island.

[edit] Clay tabletsClay tablets were used inMesopotamia in the third millennium BC. Thecalamus, an instrumentin the form of a triangle, was used to make characters in moist clay. The tablets were fired to drythem out. AtNineveh, 22,000 tablets were found, dating from theseventh century BC; this was

the archive and library of the kings ofAssyria, who had workshops of copyists andconservationists at their disposal. This presupposes a degree of organization with respect tobooks, consideration given to conservation, classification, etc.

[edit] PapyrusMain article: Papyrus
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Egyptian Papyrus

After extracting the marrow from the stems, a series of steps (humidification, pressing, drying,gluing, and cutting), produced media of variable quality, the best being used for sacred writing.In Ancient Egypt, papyrus was used for writing maybe as early as from First Dynasty, but firstevidence is from the account books of KingNeferirkare Kakai of the Fifth Dynasty (about 2400BC).[1] A calamus, the stem of a reed sharpened to a point, or bird feathers were used for writing.The script of Egyptian scribes was called hieratic, or sacredotal writing; it is not hieroglyphic,but a simplified form more adapted to manuscript writing (hieroglyphs usually being engraved orpainted).

Papyrus books were in the form of a scroll of several sheets pasted together, for a total length ofup to 10 meters or even more. Some books, such as the history of the reign of Ramses III, wereover 40 meters long. Books rolled out horizontally; the text occupied one side, and was dividedinto columns. The title was indicated by a label attached to the cylinder containing the book.Many papyrus texts come from tombs, where prayers and sacred texts were deposited (such asthe Book of the Dead, from the early 2nd millennium BC).

These examples demonstrate that the development of the book, in its material makeup andexternal appearance, depended on a content dictated by political (the histories ofpharaohs) andreligious (belief in an afterlife) values. The particular influence afforded to writing and wordperhaps motivated research into ways of conserving texts.

[edit] East Asia

A Chinese bamboo book.

Writing on bone, shells, wood and silk existed inChinaby the second century BC.Paperwasinvented in China around the 1st century AD. The discovery of the process using the bark of theblackberry bush is attributed to Ts'ai Louen, but it may be older. Texts were reproduced bywoodblock printing; the diffusion of Buddhist texts was a main impetus to large-scaleproduction.

The format of the book evolved in China in a similar way to that in Europe, but much moreslowly, and with intermediate stages of scrolls folded concertina-style, scrolls bound at one edge("butterfly books") and so on. Printing was nearly always on one side of the paper only.
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