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Home , Clock face, History of watches, Quartz clock, Spring (device), Water clock

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Clocks and

DELIA O’MEARA Systems Administrator , as water tends to drip faster when the container is he article in the November/December full, due to pressure, while it 2006 CL examined how man’s need to will drip more slowly as the T measure time led to the development container empties. of the , which is in common use in During the third-cen- our homes and offices on a daily basis. In this tury Common (CE), the article, we will continue to examine how man Chinese further developed developed a means to measure time in even the clepsydra to drive various smaller increments, which led to the develop- mechanisms, which illustrated ment of and watches through the ages. astronomical phenomena. Su Before we can begin to examine how clocks Sung built an elaborate evolved over time, we need to know what tower, which stood over 30 basic elements a clock needs. Firstly, it requires feet in height, with doors that a regular, constant and repetitive action to opened to reveal manikins mark off equal increments of time. This was unwound, the -powered clock was the which rang or , or held tablets precursor to more accurate timekeeping. achieved by means of an , which is indicating the . a type of transformer, which converts power Although Galileo Galilei is credited with What is interesting to note is that water the invention of the in 1582, it was generated via springs, water or weights, into clocks were still in common use in North a constant mechanical motion. Secondly, it Christian Huygens, a Dutch scientist, who made Africa during the early part of the twentieth the first in 1656. The - needs a means of keeping track of the incre- . ments of time and should be able to display nism in this clock used a ‘natural’ period of os- the result - clock hands or some other visual Mechanical clocks cillation. It is amazing to find that this clock had an error of less than one per . The display. During the Middle Ages, (500-1500 CE), following Huygens developed the balance Thus the of timekeeping can be seen there does not appear to have been many wheel and spring assembly, which reduced the as a search for a mechanism, which would best advances made in with regard to clock’s error to less than ten a day. meet these requirements. improving the devices used for timekeeping. Around the mid 1660s, a clock was built It seems that the , sometimes placed with a tall case which concealed the weights Sun clock, merkhet and above doorways, was the favoured device in and pendulum. These became known as use during this period. grandfather clocks. As early as 3500 Before (BCE), During the early part of the fourteenth the Egyptians used sun clocks to divide the century, large mechanical clocks, which were Clocks and navigation day into parts. The shadow cast by an obelisk, weight-driven and used a verge-and-foliot While pendulum clocks were becoming which had been carefully constructed and geo- escapement, began appearing in the tow- more and more accurate, there was still one graphically positioned, enabled people to di- ers of a number of large Italian cities. The particular hurdle to be overcome. As the vide the day into morning and afternoon. The mechanism used in these clocks, comprised Explorers left the safety of the shores to ex- addition of markers to the base of the obelisk a freely swinging horizontal bar (the foliot) plore uncharted seas, they needed a means of could indicate further subdivisions of the day. attached to a centrally-located vertical shaft determining where they were. The had The merkhet, the oldest known astronomi- (the verge). The mechanism was driven by developed the systems of latitude and longi- cal tool was developed around 600 BCE. This gravity. As the weight wrapped around tude. Measuring latitude was not a problem, made it possible to measure the night-time the spindle descended, the spindle turned but measuring was a different mat- . Two merkhets were used to establish a and a toothed crown-wheel on the spindle ter. The mariner needed to know the speed north-south meridian, by lining them up with made the escapement oscillate. The passage at which the ship was travelling, to be able to the Pole star. The crossing of this meridian by of time was measured by moving a hand calculate the distance covered each day. Every certain stars indicated the hour. around a marked . degree of longitude corresponds to four min- The Greeks began using the clepsydra, or Variations of the verge-and-foliot mecha- utes of time. The navigator needed to know water clock around 325 BCE. The clepsydra nism were used for more than 300 . the time at the starting point, as well as the lo- works on the simple principle of the flow of The next technological advance came cal time. By comparing the two , he was water either into, or out of, a container. The around 1500-1510 in Germany, with the able to calculate the current longitude relative water would drip at a nearly constant rate invention of the spring-powered clock. to the initial longitude. Ships began carrying from a small hole near the base of the con- A spring, instead of gravity, was used to clocks on board to help with calculation. tainer. Markings on the side of the container power clocks. Although these clocks were However, these early clocks, while reason- measured the hours. As you can imagine, this still not particularly accurate because the ably accurate on land, were subject to the ef- was not a very accurate method of calculating clock slowed down when the fects of the ship’s at sea and were Cape Libr., Mar/Apr 2007 44 I N T A N E T H I thus not very accurate. In 1714, Queen Anne duced. In 1869, Charles Dowd tabled a plan -made watches. They began manufac- of England offered 20 000 pounds to anyone to divide the entire into four turing watches in volume around 1880. During who could find a way to determine longitude time zones. At 12 noon on 18 November the First World War, the army found that wrist- to within half a degree. The prize was awarded 1883, the entire nation switched over to, watches were more convenient to use than in 1759 to John Harrison, a carpenter and what had previously been referred to, as pocket watches. When the war ended, soldiers self-taught clock-maker, who built a marine railroad time. The four-zone time system were allowed to keep their wristwatches. chronometer with a spring and , was legalised in 1918. After 1945, wristwatches were made more which was tested on a voyage to the West Just as coach travel and the railways had robust, with mechanisms to make them wa- Indies and was able to determine longitude to led to the adoption of uniform time in terproof, shockproof and able to function in within one-half degree. Britain and the United States, the invention extremes of pressure. The Library Service has the award-winning of Marconi’s wireless telegraph in 1899, was Battery-powered watches were marketed drama series, Longitude, made by Granada the main impetus for a worldwide system of in 1952. The new technology was embraced Film, in stock. This excellent drama tells the measuring time. The last country to adopt and developed by Asian manufacturers, story of Harrison’s quest for the first marine the Greenwich Meridian was Liberia, which particularly those in . This enabled the chronometer, which is paralleled by the story did so only in 1972. production of cheap, accurate watches acces- of Rupert Gould’s obsession to restore the sible to all. clock later. The rich and famous, on the other hand, still As strange as it may seem, the Egyptians covet wristwatches with designer labels, such as The clock and the used a portable shadow clock as early as , Tag Heuer, Audemars Piquet, Omega or new era 1500 BCE. , to name a few. Yet, cheap or expensive Perhaps the next major development in the Prior to the 1600s, timepieces were typi- - they all do one thing - tell the time. evolution of the clock is the discovery by cally driven by weights and as a result were To find out more about this interesting sub- Pierre Curie in 1880 that the application of impractical as portable timepieces. ject, see the following web sites: pressure to a quartz crystal caused it to vibrate So-called pocket watches invented in at a constant . WA Marrison built Tudor, England during the sixteenth century, Early history of clocks the first in 1928. He replaced were very large cumbersome items, often www.perseus.tufts.edu/GreekScience/Students/ the pendulum and other mechanical oscillat- worn around the neck. They served more as Jesse.CLOCK1A.html ing devices with the vibrating quartz crystal. It decoration than , as they were became possible to measure the accuracy of not particularly accurate. General history of clocks the clock up to a millionth of a . Although spiral springs were used from www.atimetoremember.net/clockhistory.html One would have thought that the clock had 1500, it was not until the use of the spiral- http://physics.nist.gov/GenInt/Time/early.html reached its ultimate achievement in accuracy. -driven mechanism in 1675, www.mystical-www.co.uk/time/clocks/htm that portable timepieces became more ac- This was not so. English physicists L Essen and www.maa.org/devlin/devlin_12_99.html J Perry constructed an even more accurate curate. The minute hand was added and the clock, the , in 1955. dial was subdivided into . Charles www.usgennet.org/usa/topic/preservation/science/ inventions/chpt5.htm Today, the satellite-based Global Positioning II introduced long in 1675 and it System (GPS), uses atomic clocks to deter- became the fashion for men to carry their Verge escapement watch in their pocket, instead of wearing it mine its position. Each satellite beams down http://en.wikipedia.org/wiki/Verge_escapement a signal giving its position and the mean time around the neck. determined by four atomic clocks it carries During the 1700s, small technical History of alarm clocks on board. The signal is picked up on a device, developments and modifications were http://clockhistory.com/alarmClockHistory/index. which is small enough to be hand-held, which made. Perhaps the greatest development html during this period was the use of ‘jewelling’, then computes its latitude and longitude. The Grandfather clocks on-board atomic clocks are accurate to one invented by John Arnold. ‘Jewelling’ refers to second in 30 000 years, while ground-based the use of precious stones, such as rubies, www.grandfatherclocksplus.com/cgi-bin/gfcp/history. atomic clocks can be accurate up to one sec- as bearings to reduce friction. By 1800, an html ond in 1 400 000 years! accurate watch, in the form of a pocket www.clocktypes.com/history_gransfather_clocks. chronometer, was available. A second hand html was added. http://theclockdepot.com/history_of_the_ Initially in the eighteenth century, the ‘time of Up to 1840, watches were all hand- grandfather_clock.html finished and as a result parts were not day’ varied from town to town. This made Cuckoo clocks it very difficult for the mail coach service to inter-changeable. It was the Swiss who be- keep to a timetable, because coachmen had to lieved that there was a market for cheaper, www.clockstop.com/perl/csCuckooClocks.pl adjust their watches to give the correct local Mystery clocks time. www.roger-russell.com/mysteryclocks/mysteryclocks. With the introduction of the railway net- htm work in England in the nineteenth century, the problem became worse. As a result the History of watches railroads in England decided to adopt www.clocksonly.com/watch_history.html time, as determined by the Royal Observatory www.nawcc.org/museum/nwcm/galleries/ at Greenwich, for their network. By 1855 all pocketwatch/pocketwatch.htm public clocks throughout Great Britain had www.lussori.com/watch-history.html adopted GMT (Greenwich Mean Time). www.watches.co.uk - Click on Information The greater distances involved in the United States caused even greater confusion than in Learning about time Britain. In order to bring some order into the www.arcytech.org/java/clock/index.html existing chaos, regional time zones were intro- 2 0 0 7 Kaapse Bib l., Mar/Apr 2007 45