and they had sunk to three or four hundred feet in height, but in no place did we find any point where they could be ascended. If anything, they were more impossible than at the first point where we had met them. Their absolute steepness is indicated in the photograph which I took over the stony desert.
"Surely," said I, as we discussed the situation, "the rain must find its way down somehow. There are bound to be water-channels in the rocks."
"Our young friend has glimpses of lucidity," said Professor Challenger, patting me upon the shoulder.
"The rain must go somewhere," I repeated.
"He keeps a firm grip upon actuality. The only drawback is that we have conclusively proved by ocular demonstration that there are no water channels down the rocks."
"Where, then, does it go?" I persisted.
"I think it may be fairly assumed that if it does not come outwards it must run inwards."
"Then there is a lake in the centre."
"So I should suppose."
"It is more than likely that the lake may be an old crater," said Summerlee. "The whole formation is, of course, highly volcanic. But, however that may be, I should expect to find the surface of the plateau slope inwards with a considerable sheet of water in the centre, which may drain off, by some subterranean channel, into the marshes of the Jaracaca Swamp.
