A PHILOSOPHIC ENCYCLOPEDIA OF 155
equator the divergence is least; and it increases the further North we go because a planetary hour is one twelfth part of the time between Sunset on a particular day and Sunrise the next morning, or it is one twelfth part of a particular day beginning at Sunrise and ending at Sunset.
At the equinoxes when the day and night are of equal length, the planetary hours are also sixty minutes each, but at midsummer and in latitude sixty where the Sun rises at 3 A. M. and sets at 8 P. M. giving a day of seventeen and a night of only seven hours, the planetary hours of the day are ninety-two minutes long against twenty-seven minutes for the night hours. This is reversed in December, for then the Sun does not rise till 9:15 A. M. in latitude sixty North and it sets at 2:45 P. M. with the result that the planetary hours of the day are twenty-seven minutes long, and the night hours ninety-two minutes.
For the convenience of students we give in the back of this book six tables, each usable for two months in the year by all who live in latitude 25 to 55 North or South, this being practically the whole civilized world. They are perpetual and may be used a lifetime.
To find which planet rules a certain hour, look at your timepiece and consult the table for the current mouth. Run your index-finger down the column for the latitude in which you live. Stop when you come
