3. Posidonius blames Polybius for asserting that the region of the earth, situated under the equator, is the highest, since a spherical body being equal all round, no part can be described as high; and as to mountainous districts, there are none under the equator, it is on the contrary a flat country, about the same level as the sea; as for the rains which swell the Nile, they descend from the mountains of Ethiopia. Although advancing this, he afterwards seems to adopt the other opinion, for he says that he fancies there may be mountains under the equator, around which the clouds assembling from both of the temperate zones, produce violent rains. Here is one manifest contradiction; again, in stating that the land under the equator is mountainous, another contradiction appears. For they say that the ocean is confluent, how then can they place mountains in the midst of it? unless they mean to say that there are islands. However, whether such be the fact does not lie within the province of geography to determine, the inquiry would better be left to him who makes the ocean in particular his study. 4. Posidonius, in speaking of those who have sailed round Africa, tells us that Herodotus was of opinion that some of those sent out by Darius actually performed this enterprise;[645] and that Heraclides of Pontus, in a certain dialogue, introduces one of the Magi presenting himself to Gelon,[646] and declaring that he had performed this voyage; but he remarks that this wants proof. He also narrates how a certain Eudoxus of Cyzicus,[647] sent with sacrifices and oblations to the Corean games,[648] travelled into Egypt in the reign of Euergetes II.;[649] and being a learned man, and much interested in the peculiarities of different countries, he made interest with the king and his ministers on the subject, but especially for exploring the Nile. It chanced that a certain Indian was brought to the king by the [coast]-guard of the Arabian Gulf. They reported that they had found him in a ship, alone, and half dead: but that they neither knew who he was, nor where he came from, as he spoke a language they could not understand. He was placed in the hands of preceptors appointed to teach him the Greek language. On acquiring which, he related how he had started from the coasts of India, but lost his course, and reached Egypt alone, all his companions having perished with hunger; but that if he were restored to his country he would point out to those sent with him by the king, the route by sea to India. Eudoxus was of the number thus sent. He set sail with a good supply of presents, and brought back with him in exchange aromatics and precious stones, some of which the Indians collect from amongst the pebbles of the rivers, others they dig out of the earth, where they have been formed by the moisture, as crystals are formed with us.[650]