Chap. 74 (72.) — Remarks on Dials, as Connected With This Subject
The same dial-plates505 cannot be used in all places, the shadow of the sun being sensibly different at distances of 300, or at most of 500 stadia506. Hence the shadow of the dial-pin, which is termed the gnomon, at noon and at the summer solstice, in Egypt, is a little more than half the length of the gnomon itself. At the city of Rome it is only 1⁄9 less than the gnomon, at Ancona not more than 1⁄35 less, while in the part of Italy which is called Venetia, at the same hour, the shadow is equal to the length of the gnomon507.