Rivers and the fiery heaven: why water abounds

And why should I list the rest of the rivers born from the Rhipaean mountains, the heights beyond the innermost part of Scythia? Among them is the Rhone, along with countless other rivers, themselves navigable, which pass by the western Gauls and Celts and the barbarians bordering them, and all pour into the western sea. Others come from the south, from above through Ethiopia: some flow toward our sea, while others empty into the sea beyond the one that is sailed. There are the Aegon, the Nyses, and the one called Chremetes, and besides these the Nile, whose nature is not even like that of rivers when it floods Egypt like a sea. So the region of our inhabited world is surrounded by water, bound by immense seas and watered by countless ever-flowing rivers, through the ineffable wisdom of the One who arranged that the nature opposed to fire should be hard to consume. Yet there will come a time when all things will be burned up by fire, as Isaiah says in the words he addresses to the God of all: 'He who says to the deep, You shall be made desolate, and I will dry up all your rivers' (Isaiah 44:27). Therefore cast away the wisdom that has become foolish, and accept with us the teaching of truth, plain in its speech but infallible in its knowledge.

For this reason: 'Let a firmament come into being in the midst of the water, and let it separate water from water' (Genesis 1:6). We have already said what the name 'firmament' means in Scripture. It does not mean a resistant and solid nature, one that has weight and offers resistance—Scripture does not call that a firmament. If it did, the earth would more properly have been given that name. But because the nature of the things above is fine and loose and not graspable by any sense, Scripture named it 'firmament' by comparison with the finest things that are imperceptible to the senses. And understand it as a place that separates the moist element: the fine and filtered part passes through to the upper regions, while the thickest and earthiest part is released below, so that from beginning to end the same good temperature may be preserved, as the moist elements are gradually drawn off in part. But you distrust the abundance of water, while you do not consider the abundance of heat—which, even if small in size, is capable of consuming a great deal of moisture because of its power. For it draws in the moisture that lies near it, as the cupping glass shows; and it consumes what it has drawn in, like the fire of a lamp, which draws up the fuel that lies near it through the wick and quickly turns it to ash through the change. And who doubts that the ether is fiery and burning hot? If it were not held back by the necessary limit set by its Maker, what would prevent it from setting everything ablaze and burning up all that is near it, consuming at once all the moisture in all things? For this reason there is aerial water, as the upper region becomes cloudy from the rising of vapors that rivers and springs and marshes and lakes and seas all send forth, so that the ether may not seize everything and set it on fire. Indeed, we see this very sun, in the summer season, often leaving a soaked and marshy land completely dry and parched in the briefest moment of time.