Geography

​He also errs in the next argument, in which he wishes to conclude that the road from Thapsacus to the Caspian Gates, which Eratosthenes has stated to be ten thousand stadia, is not measured in a straight line but is delivered as if in a straight line, although the straight line is much shorter. His approach is as follows. He says that, according to Eratosthenes, the meridian through the Canopic mouth and the one through the Cyaneae are the same, and that this meridian is six thousand three hundred stadia distant from the one through Thapsacus, and the Cyaneae are six thousand six hundred stadia distant from the Caspian mountain, which lies at the pass leading from Colchis to the Caspian Sea, so that, with a difference of three hundred stadia, the distance from the meridian through the Cyaneae to Thapsacus and to the Caspian mountain is equal; and that in a certain way, both Thapsacus and the Caspian mountain lie on the same meridian. And from this, he says, it follows that the Caspian Gates are equally distant from both Thapsacus and the Caspian mountain, being distant by much less than the ten thousand stadia which Eratosthenes says they are distant from Thapsacus, and therefore the straight-line distance is much less than ten thousand. Thus, he calculates that the ten thousand is a roundabout route, while Eratosthenes calculates in a straight line from the Caspian Gates to Thapsacus. But we shall say to him that, while Eratosthenes takes straight lines with a certain latitude, which is appropriate to geography, and likewise takes both meridians and lines towards the equinoctial sunrise with latitude, Hipparchus corrects him geometrically, as if one would take each of these with instruments, though he himself does not take either right angles or parallels with instruments but rather by conjecture. This is indeed one error; another is that the distances laid down by Eratosthenes are not even assumed by him, nor is the refutation brought against them, but against those fabricated by himself. For whereas Eratosthenes spoke of the distance from the mouth to Phasis as eight thousand stadia, and added the six hundred from there to Dioscurias, and the pass from Dioscurias to the Caspian mountain as a journey of five days, which according to Hipparchus himself is conjectured to be spoken of as about a thousand stadia, so that the sum total according to Eratosthenes amounts to nine thousand six hundred; Hipparchus himself has shortened it and says that from the Cyaneae to Phasis is five thousand six hundred, and from there to the Caspian mountain another thousand; so that it would not be according to Eratosthenes that the Caspian mountain and Thapsacus are on somehow the same meridian, but according to himself. But let it be according to Eratosthenes; how then does it follow from this that the distance from the Caspian mountain to the Caspian Gates is equal to that from Thapsacus to the same point?