The equal distance of the sun from all nations (according to Onesicritus) is an argument addressed to the senses, and not to reason. But it is not an argument addressed to the senses generally, but in the meaning that the earth bears the proportion of a point to the sun, for we may understand such a meaning of an argument addressed to the senses, by which we estimate heat to be more or less, as it is near or at a distance, in which cases it is not the same; and in this meaning, not in that of Onesicritus, the sun is said to be near the Ethiopians.
25. It is admitted by those who maintain the resemblance of India to Egypt and Ethiopia, that the plains which are not overflowed do not produce anything for want of water.
Nearchus says, that the old question respecting the rise of the Nile is answered by the case of the Indian rivers, namely, that it is the effect of summer rains; when Alexander saw crocodiles in the Hydaspes, and Egyptian beans in the Acesines, he thought that he had discovered the sources of the Nile, and was about to equip a fleet with the intention of sailing by this river to Egypt; but he found out shortly afterwards that his design could not be accomplished,
“for in midway were vast rivers, fearful waters, and first the ocean,”[355]
into which all the Indian rivers discharge themselves; then Ariana, the Persian and Arabian Gulfs, all Arabia and Troglodytica.
The above is what has been said on the subject of winds and rains, the rising of rivers, and the inundation of plains.
26. We must describe these rivers in detail, with the particulars, which are useful for the purposes of geography, and which have been handed down to us by historians.
Besides this, rivers, being a kind of physical boundaries of the size and figures of countries, are of the greatest use in every part of the present work. But the Nile and the rivers in India have a superiority above the rest, because the country could not be inhabited without them. By means of the rivers it is open to navigation and capable of cultivation, when otherwise it would not be accessible, nor could it be occupied by inhabitants.
We shall speak of the rivers deserving notice, which flow into the Indus, and of the countries which they traverse; with regard to the rest we know some particulars, but are ignorant of more. Alexander, who discovered the greatest portion of this country, first of all resolved it to be more expedient to pursue and destroy those who had treacherously killed Darius, and were meditating the revolt of Bactriana. He approached India therefore through Ariana, which he left on the right hand, and crossed the Paropamisus to the northern parts, and to Bactriana.[356] Having conquered all the country subject to the Persians, and many other places besides, he then entertained the desire of possessing India, of which he had received many, although indistinct, accounts.
He therefore returned, crossing over the same mountains by other and shorter roads, having India on the left hand; he then immediately turned towards it, and towards its western boundaries and the rivers Cophes and Choaspes.[357] The latter river empties itself into the Cophes,[358] near Plemyrium, after passing by another city Gorys, in its course through Bandobene and Gandaritis.[359]