23. Having in this manner but imperfectly traced the outlines of his second section, the third section, for various reasons, is still less exact. The first cause has been already explained, viz. that the line from the Caspian Gates to Carmania is not clearly defined, as the side of the section is common both to the third and second sections. Secondly, on account of the Persian Gulf interrupting the continuity of the southern side, as he himself tells us, he has been obliged to take the measured road running through Susa and Persepolis to the boundaries of Carmania and Persia, and suppose it straight.[554] This road, which he calls the southern side, is a little more than 9000 stadia. He does not, however, tell us, that it runs parallel to the northern side. It is also clear that the Euphrates, which he makes the western boundary, is any thing but a straight line. On leaving the mountains it flows south, but soon shifts its course to the east; it then again pursues a southerly direction till it reaches the sea. In fact, Eratosthenes himself acknowledges the indirect course of this river, when he compares the shape of Mesopotamia, which is formed by the junction of the Tigris and Euphrates, to the cushion on a rower’s bench. The western side bounded by the Euphrates is not entirely measured; for he tells us that he does not know the extent of the portion between Armenia and the northern mountains,[555] as it has not been measured. By reason of these hinderances he states that he has been only able to give a very superficial view of the third section, and that his estimate of the distances is borrowed from various Itineraries, some of them, according to his own description, anonymous. Hipparchus therefore must be considered guilty of unfairness, for criticising with geometrical precision a work of this general nature. We ought rather to be grateful to a person who gives us any description at all of the character of such [unknown] places. But when he urges his geometrical objections not against any real statement of Eratosthenes, but merely against imaginary hypotheses of his own creation, he shows too plainly the contradictory bent of his mind.