A lengthier demonstration goes as follows. In its passage over the inland parts of Libya [17,25] (nation), AfricaLibya, the sun does this: as the air is always clear in that region, the land warm, and the winds cool, the sun does in its passage exactly as it would do in the summer passing through the middle of the heaven:

it draws the water to itself, and having done so, expels it away to the inland regions, and the winds catch it and scatter and dissolve it; and, as is to be expected, those that blow from that country, the south and the southwest, are the most rainy of all winds.

Yet I think that the sun never lets go of all of the water that it draws up from the Nahr an- Nil [31.1,30.166] (river), AfricaNile yearly, but keeps some back near itself. Then, as the winter becomes milder, the sun returns to the middle of the heaven, and after that draws from all rivers alike.

Meanwhile, the other rivers are swollen to high flood by the quantity of water that falls into them from the sky, because the country is rained on and cut into gullies; but in the summer they are low, lacking the rain and being drawn up too by the sun.

But the Nahr an- Nil [31.1,30.166] (river), AfricaNile, being fed by no rain, and being the only river drawn up by the sun in winter, at this time falls far short of the height that it had in summer; which is but natural; for in summer all other waters too and not it alone are attracted to the sun, but in the winter it alone is afflicted.