SOME EARLY FORMS OF CLOCKS

Evening Star, Issue 22572, 13 February 1937, Page 8

SOME EARLY FORMS OF CLOCKS

As you all know, a day and night is 24 hours—the time it takes the earth to make one revolution; but one of the first things man. had to do was find some means of telling exactly what time of the day or night it was at any given minute. The earliest method was a very simple but alas! inaccurate one. King Alfred, we learn, made candles of certain thickness and marked divisions down the side. As tho candle burnt, down to each division it showed that an hour had passed; but the trouble was that any draught of air or a variation in the composition of the candle caused it to burn faster and thus record incorrectly. The next step was the sundial, tho )irinoipl« of which was that the sun threw the shadow of a piece of metal on to a plate or dial marked off in hours. As the day wore on the shadow moved round denoting the various hours. The main trouble, of course, was that the sundial was useless unless the sun was shining.

Another early method was the watet clock. This consisted of a tank with a small hole from which water dripped at a certain rate. A float made of wood rested on tho water with an attachment which pulled the hand of the dial round as the water sank in the tank* This method could only record thi hours, and rather unreliably at that. A later method was the use of the hour glass, which was a glass vessel shaped like a figure 8. The waist, or middle, was very narrow, and just sufficient fine sand was placed in the top half as would run through the small waist to the bottom in an hour. ' In some houses a little hour glass is still used to-day as an “egg boiler.’.’ The sand takes three minutes to .empty from one half of the glass to the other. Then came tho pendulum clock, with both hour and'mmute hands. The next advance was a coiled spring to pull the wheels round instead of relying on a weight and This is what is known as the mainspring of our modern clocks and watches, and, as wo all know, the modem article is a wonderful timekeeper.