Kitap 9
14
The most important operation in astronomy is the calculation of the lengths of the days and nights. If these had been uniform it would not have been a matter requiring any study, but the knowledge would have been common to all the world: since however they not only differ with each other but also with themselves, it is plainly necessary to be acquainted with the increase and diminution of both the one and the other. How can a man calculate a march, and the distance practicable in a day or in a night, if he is unacquainted with the variation of these periods of time? In fact nothing can be done up to time without this knowledge,—it is inevitable otherwise that a man should be sometimes too late and sometimes too soon. And these operations are the only ones in which being too soon is a worse fault than being too late. For the general who overstays the proper hour of action only misses his chance, since he can find out that he has done so before he arrives, and so get off safely: but he that anticipates the hour is detected when he comes up; and so not only misses his immediate aim, but runs a risk of ruining himself altogether.
