"Think," was Milton's answer, "of all the rivers that, for how many millions of years no man can tell, have been running into the sea, and yet the sea is not overflowing."
"I don't see the application of that to this underground world, don't see how all the water—there must be more streams than this one—can possibly return as vapor to the region above."
"I admit," Rhodes said, "that the problem is a formidable one and that, with our present paucity of data, we can not hope to solve it. Still I think that my suggestion is sound."
"But where are the openings to permit the escape of so enormous, for enormous it must be, amount of water-vapor?"
"There may be countless vents, fissures, Bill, ways of egress that man will never know. Whatever the explanation, there can be no doubt that the water is going down and that this subterranean world into which we have found our way is not full."
"But where does it go? Down to some sunless sea perhaps, though, if that hypothesis of yours is a sound one, bathed in light, a light never seen, in that world we have left, on land or sea."
Rhodes was silent for a moment, leaning on his alpenstock. Then:
"It is strange truly, the descent of the waters. And yet it would not, I believe, have been to you so very strange a thing had you known that the sea itself flows into the earth."
"The sea itself?"
Rhodes nodded.