“Here is the lower jaw of a mastodon,” 11 I said. “These are the molar teeth of the Deinotherium; this femur must have belonged to the greatest of those beasts, the Megatherium. It certainly is a menagerie, for these remains were not brought here by a deluge. The animals to which they belonged roamed on the shores of this subterranean sea, under the shade of those arborescent trees. Here are entire skeletons. And yet I cannot understand the appearance of these quadrupeds in a granite cavern.”

“Why?”

“Because animal life existed upon the earth only in the secondary period, when a sediment of soil had been deposited by the rivers, and taken the place of the incandescent rocks of the primitive period.”

“Well, Axel, there is a very simple answer to your objection that this soil is alluvial.”

“What! at such a depth below the surface of the earth?”