VIII
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I do not, indeed, suppose that you will long hesitate to believe that there are underground rivers and a hidden sea. From what other cause could the rivers burst out and come to the surface unless the source of the moisture were shut up within the earth? For instance, when one sees the Tigris interrupted and dried up in the middle of its course, not diverted as a whole, but gradually with imperceptible losses first lessen and then waste away, where do you suppose it goes to if not to the depths of the earth, especially as you see it emerge again not less in volume than its former stream? And what are you to say when you see the Alpheus, so celebrated by the poets, sink in Achaia and, having crossed beneath the sea, pour forth in Sicily the pleasant fountain Arethuse? And don’t you know that among the explanations given of the occurrence of the inundation of the Nile in summer, one is that it bursts forth from the ground, and is swollen not by rain from above but by water given out from within the earth?
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I have myself heard from their own lips the story told by the two non-commissioned officers sent to investigate the sources of the Nile by our good Emperor Nero, a monarch devoted to virtue in every form, but especially solicitous for the interests of truth. The King of Ethiopia had supplied them with assistance and furnished letters of introduction to the neighbouring kings, and so they had penetrated into the heart of Africa and accomplished a long journey. “We came indeed,” I give their own words, “to huge marshes, the limit of which even the natives did not know, and no one else could hope to know; so completely was the river entangled with vegetable growth,80 so impassable the waters by foot, or even by boat, since the muddy overgrown marsh would bear only a small boat containing one person. There,” my informants went on, “we saw with our eyes two rocks from which an immense quantity of water issued.” Now whether that is the real source or only an addition to the river; whether it rises there or merely returns to the surface after its previous course underground; don’t you think that, whatever it is, that water comes up from a great lake in the earth? The earth must contain moisture scattered in numerous places and collected at depth in order to be able to belch it out with such violence.