THE SUN AS TIMEPIECE

Taranaki Daily News, 15 August 1931, Page 17 (Supplement)

THE SUN AS TIMEPIECE

NATURE TO ARTIFICE

(By

Rev. B. Dudley

F.R.A.S.)

Modern life is so -far governed by the artificial that we are scarcely aware of our indebtedness to Nature. Without in-

tending it, or even thinking about it, we have come to regard Nature as something almost- independent of the advancement and organisation of human life as “if it had nothing to do with our-daily activities.” As a modern essayist writes: “We are becoming so completely fettered by the bondage of mechanical drudgery, so enveloped in the cities’ endless turmoil, that we have forgotten Nature altogether.”. So dependent have we become upon the clock as to have forgotten that the Sun was the original timepiece; that there was a long period in the history of mankind when, indeed, no other means existed for the measurement of time. It is of historical interest to go back in imagination to the remote past, and to see our ancestors at work. Let us try to visualise them out there among the canyons of New Mexico and Arizona, for example, where there yet remain some of the homes built in the hollows and on the ledges of the cliffs during prehistoric days. They are the predecessors of the Pueblo Indians still found in these regions) Even those ancient cliff-dwell-ers must have looked up to the sun in worshipful awe, as they watched its daily passage across the sky.

Picture the scene —the cliff-dweller going forth on his daily hunt for food; the women' left behind, and measuring the length of the passing day by the shadows on the face of the cliffs, so that she may have some idea of the time of his expected return. It was early dawn when he left. But the sun is climbing higher in the heavens, and thus the shadow of the opposite wall is steadily moving downward as the sun continued to mount. The cliffs face each other, and while all the morning the shadow has crept down the wall on one side until noon, when the whole, of the narrow canyon was illuminated by the solar rays, it now begins to rise on the opposite cliff-face. It is time for the hunter to return with the results of his expedition. For he, too, has his shadow-signs, and knows the hour with rough approximation to the truth. And so, ere the shadow has advanced far up the wall opposite tlie one on which it rested in the morning, the body bf the animal fracked and killed has been eaten. These walls were the cliff-dwellers’ clock, while the advancing shadow was its -tell-tale hand.

. It would not be long before stick or stone would be planted, where there was no tree or rock, in such position as to cast the desired shadow. Throughout succeeding days this pole or stone would mark the point where the shadow fell when the sun was highest in the sky. Now, for the first time, man has gone beyond the -provision Nature has made for him, and he has adopted a device by which to mark his day into something like definite intervals. Bye and bye a circle of stones is made; and a stick, suitably placed, throws a shadow on stone after stone and tells him with still more exactness the time. Here is the first sundial —for centuries the forerunner of the clock.

It was soon found, however, that as the year advanced and. the sun went first north and then south, the shadow underwent a change, so that the sundial was at times behind and at other times ahead of itself, so to speak. A recent writer on scientific subjects tells how these shadow-irregularities were got over in the third century before Christ. “Berosus, a Babylonian priest, living about the year 250 8.C., came to the rescue here and hit on a clever way to get round this trouble caused by the north and sound movement of the sun. He made his dial hollow like tho inside of- a bowl so that it would reflect accurately the movement of the sun in the great upside-down bowl of the sky. His pointer was put above this, witli a little round ball on the end, and the time was marked by the shadow of this ball. A vertical pointer, standing upright like a tree, would not have worked; but with this horizontal pointer reaching out over the bowl he was able to get the result he wanted. However the sun moved, the shadow moved in the bowl just as the sun appeared to move in the arching sky. By an ingenious set of lines' of longitude drawn across the bowl, he got a dial or ‘hemicycle’ (half circle) which kept time fairly accurately all the year round.”

All through the middle ages, too, sundials of various kinds were employed. But what was to be done for the time during cloudy weather ? One of these dials bore the appropriate inscription: “I count but sunny hours.” They were indeed very imperfect devices, growing more and more unsuitable ,as civilisation moved forward, and the need for constancy and accuracy increased. In due time came the “Water Thief,” as it was called. The predecessor of this form of timepiece was the waterjar, used in China. A somewhat inventive slave, employed in a garden, had placed a jar, with a tiny hole in tho bottom, in such a position that the water from it would drip slowly on a plant situated beneath, instead of pouring upon it all at once. Thus was suggested a kind of timepiece, the flow of water being properly regulated so as to indicate time, and workable under all weather conditions. Such time-measurers were used in China as far back as 3000 8.C., possibly earlier. The Hindus made •use of a copper bowl with a small hole on its underside. The bowl was set to float in a vessel partly filled with water. Gradually it would sink to the bottom as the water in the vessel pushed its way up through tlie tiny aperture. A servant whose duty it was to watch would lift the bowl,* and, after emptying it, strike it with a rod prepared for the purpose, so as to notify to the household that another time-interval had gone, and then he would set it afloat once more.

The Water Thief as used by the Egyptians,and Babylonians was so constructed that a float was gradually raised by means of water dropping from a small hole above. As the float rose it indicated the hour by a scale of numbers marked at the side of the vessel. Later, by a more elaborate arrangement, a hand was made to'turn on a dial as the float mounted. This was the clepsydra such as Tycho Brake used in his astronomical observatory at Urainburg toward the end:of the 10th century.