19.

Again, Eratosthenes wished to show the ignorance of Deimachus, and his want of information concerning such matters, as proved by his assertion that India lies between the autumnal equinox539 and winter tropic.540 Also in his blaming Megasthenes, where he says that in the southern parts of India the Greater and Lesser Bear are seen to set, and the shadows to fall both ways; assuring us that such is not the case in India.541 These assertions, says Eratosthenes, arise from the ignorance of Deimachus. For it is nothing else than ignorance to suppose that the autumnal equinox is not equally distant from the tropics with the vernal; since in both equinoxes the sun rises at the same point, and performs a similar revolution. Further, [he continues,] the distance from the terrestrial tropic to the equator, between which, according to Deimachus himself, India is situated, has been proved by measurement to be much less than 20,000 stadia, consequently his own statements prove that my assertion is correct, and not his. For supposing India to be twenty or thirty thousand stadia [in breadth] it could not be contained in the given space, but if my estimate be taken it is simple enough. It is another evidence of his want of information, to say that the two Bears are not seen to set, or the shadows to fall both ways, in any part of India, since 5000 stadia south of Alexandria542 both of these phenomena are observable. Thus reasons Eratosthenes; whom Hipparchus again criticises in the same mistaken way. First he substitutes [in the text of Deimachus] the summer in place of the winter tropic; then he says that the evidence of a man ignorant of astronomy ought not to be received in a mathematical question; as if Eratosthenes in the main had actually been guided by the authority of Deimachus. Could he not see that Eratosthenes had followed the general custom in regard to idle reasoners, one means of refuting whom is to show that their arguments, whatever they may be, go only to confirm our views.