Figure 18 represents a clock which is a work of art and shows great refinement of design in providing for the varying lengths of days. The bar lying across the dial is fastened to the weight through the two slits running the whole length of the dial. On this cross bar is a small pointer, which is movable by the fingers, and may be set to any one of the thirteen vertical lines. The numerous characters on the top space of dial indicate the dates on which the pointer is to be set. This clock is wound up at sunset, and it is easy to see that as the little pointer is set towards the right, the night hours at the top of the dial become shorter and the day hours longer on the lower part. The left edge of the dial gives the hours, reading downwards, and as the pointer touches any one of the curved lines the hour is read at the left-hand end. The curved lines formed of dots are the half-hours. The right-hand edge of the dial has the "twelve horary characters" which will be explained later. For dividing the varying days into six hours' sunshine it would be difficult to think of a more artistic and beautiful invention than this. It is a fine example of great ingenuity and constant trouble to operate a system which is fundamentally wrong according to our method of uniform hours at all seasons. Clocks having these curved lines for the varying lengths of days--and we shall find them on circular dials as we go on--must be made for a certain latitude, since the days vary more and more as you go farther from the equator. This will become plain when you are reminded that a Japanese clock at the equator would not need any adjustment of hour numerals, because the days and nights are equal there all the year. So after such infinite pains in forming these curved lines the clock is only good in the latitude for which it was made and must not be carried north or south! Our clocks are correct from pole to pole, but all clocks must be set to local time if they are carried east or west. As this is a rather fascinating phase of the subject it might be worth pointing out that if you go north till you have the sun up for a month in the middle of summer--and there are people living as far up as that--the Japanese system would become absurd and break down; so there is no danger of any of our polar expeditions carrying Japanese clocks. [Illustration: Fig. 16--Japanese Clock with Vertical Dial, Weight and Balance.] [Illustration: Fig. 17--Japanese Vertical Dials] [Illustration: Fig. 18--Japanese Clock with Vertical Dial Having Curved Lines, Weight and Balance.]