"And, such, indeed, is the nature of the whole earth, and the parts about the earth; but there are many places all round it throughout its cavities, some deeper and more open than that in which we dwell; but others that are deeper have a less chasm than our region, and others are shallower in depth than it is here, and broader. 139. But all these are in many places perforated one into another under the earth, some with narrower and some with wider channels, and have passages through, by which a great quantity of water flows from one into another, as into basins, and there are immense bulks of ever-flowing rivers under the earth, both of hot and cold water, and a great quantity of fire, and mighty rivers of fire, and many of liquid mire, some purer, and some more miry, as in Sicily there are rivers of mud that flow before the lava, and the lava itself, and from these the several places are filled, according as the overflow from time to time happens to come to each of them. But all these move up and down, as it were, by a certain oscillation existing in the earth. And this oscillation proceeds from such natural cause as this; one of the chasms of the earth is exceedingly large, and perforated through the entire earth, and is that which Homer[43] speaks of, 'very far off, where is the most profound abyss beneath the earth,' which elsewhere both he and many other poets have called Tartarus. For into this chasm all rivers flow together, and from it flow out again; but they severally derive their character from the earth through which they flow. 140. And the reason why all streams flow out from thence, and flow into it, is because this liquid has neither bottom nor base. Therefore, it oscillates and fluctuates up and down, and the air and the wind around it do the same; for they accompany it both when it rushes to those parts of the earth, and when to these. And as in respiration the flowing breath is continually breathed out and drawn in, so there the wind oscillating with the liquid causes certain vehement and irresistible winds both as it enters and goes out. When, therefore, the water rushing in descends to the place which we call the lower region, it flows through the earth into the streams there, and fills them, just as men pump up water. But when again it leaves those regions and rushes hither, it again fills the rivers here; and these, when filled, flow through channels and through the earth, and, having severally reached the several places to which they are journeying, they make seas, lakes, rivers, and fountains. 141. Then, sinking again from thence beneath the earth, some of them having gone round longer and more numerous places, and others round fewer and shorter, they again discharge themselves into Tartarus--some much lower than they were drawn up, others only a little so; but all of them flow in again beneath the point at which they flowed out. And some issue out directly opposite the