The ancient methods of dividing day and night in China and Japan become more hazy as we go backwards and the complications grow. The three circles in [Fig. 1] (Chapter I) are all taken from Japanese clocks, but the interpretation has been obtained from Chinese and Japanese scholars. The Japanese obtained a great deal from the Chinese, in fact nearly everything relating to the ancient methods of time keeping and the compiling of calendars. I have not been able to find any Chinese clocks constructed of wheels and pinions, but have a number of Japanese. These have a distinct resemblance to the earlier Dutch movements, and while made in Japan, they are practically Dutch, so far as the “works” are concerned, but it is easy to see from the illustrations that they are very Japanese in style and ornamentation. The Dutch were the leaders in opening Japan to the European nations and introduced modern mathematics and clocks from about 1590 A. D. The ancient mathematics of Japan came largely from China through Corea. In [Fig. 11] are given the Japanese figures beside ours, for the reader's use as a key. The complete day in Japan was divided into twice six hours; that is, six for daylight and six for night, and the clocks are set, as the days vary in length, so that six o'clock is sunrise and sunset. The hour numerals on [Fig. 12] are on little plates which are movable, and are shown set for a long day and a short night.
Fig. 11
In [Fig. 13] they are set for short days and long nights. The narrow plates shown in solid black are the half-hour marks. In this type the hand is stationary and always points straight upward. The dial rotates, as per arrow, once in a full day. This style of dial is shown on complete clocks, [Fig. 14] being a weight clock and [Fig. 15] a spring clock with chain and fusee. The hours are 9 to 4 and the dials rotate to make them read backwards. The six hours of daylight are 6, 5, 4, 9, 8, 7, 6 and the same for night, so these hours average twice as long as ours. Note that nine is mid-day and mid-night, and as these do not change by long and short days they are stationary on the dial, as you can easily see by comparing [Figs. 12] and [13], which are the same dial set for different seasons. Between these extremes the dial hours are set as often as the owner wishes; so if he happens to correspond with our “time crank” he will set them often and dispute with his neighbors about the time. [Figure 16] shows a clock with the hour numerals on a vertical series of movable plates and it is set for uniform hours when day and night are equal at the equinox. The ornamental pointer is fastened to the weight through the vertical slit, plainly visible in illustration, and indicates the time as it descends. This clock is wound up at sunset, so the six on the top of the dial is sunset the same as the six on the bottom. [Figure 17] shows how this type of dial is set for long and short days and explains itself, but will become plainer as we proceed. This dial is virtually a continuation of the old method of marking time by the downward motion of the water in the clepsydras and will be noticed later.
Figs. 12 and 13.
Japanese Dials Set for Long and Short Days