Clocks and Watches

I N T A N E T H I Clocks and watches DELIA O’MEARA Systems Administrator time, 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 calendar, which is in common use in During the third-cen- our homes and offices on a daily basis. In this tury Common Era (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 clocks and watches through the ages. astronomical phenomena. Su Before we can begin to examine how clocks Sung built an elaborate clock 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 spring-powered clock was the which rang bells or gongs, or held tablets precursor to more accurate timekeeping. achieved by means of an escapement, which is indicating the hour. 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 pendulum 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 pendulum clock in 1656. The mecha- needs a means of keeping track of the incre- century. 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 minute per day. The display. During the Middle Ages, (500-1500 CE), following year Huygens developed the balance Thus the history 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 technology with regard to clock’s error to less than ten seconds a day. meet these requirements. improving the devices used for timekeeping. Around the mid 1660s, a clock was built It seems that the sundial, 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 water clock use during this period. grandfather clocks. As early as 3500 Before Common Era (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 Greeks 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 longitude was a different mat- hours. 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 clock face. 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 years. 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 times, 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 mainspring fects of the ship’s movement 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 machine-made watches. They began manufac- of England offered 20 000 pounds to anyone to divide the entire United States 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 balance wheel, 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 watch manufacturers, story of Harrison’s quest for the first marine the Greenwich Meridian was Liberia, which particularly those in Japan. 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 centuries later. History of watches 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 Quartz clock and the used a portable shadow clock as early as Rolex, Tag Heuer, Audemars Piquet, Omega or new era 1500 BCE. Cartier, 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 frequency. WA Marrison built Tudor, England during the sixteenth century, Early history of clocks the first quartz clock 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 timekeepers, 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 second. 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.

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