"What's that you are saying?" he asked. "See," I said, pointing to the varied series of sandstones and limestones, and the first indication of slate. "Well?" "We are at the period when the first plants and animals appeared." "Do you think so?" "Look close, and examine." I obliged the Professor to move his lamp over the walls of the gallery. I expected some signs of astonishment; but he spoke not a word, and went on. Had he understood me or not? Did he refuse to admit, out of self-love as an uncle and a philosopher, that he had mistaken his way when he chose the eastern tunnel? or was he determined to examine this passage to its farthest extremity? It was evident that we had left the lava path, and that this road could not possibly lead to the extinct furnace of Snæfell. Yet I asked myself if I was not depending too much on this change in the rock. Might I not myself be mistaken? Were we really crossing the layers of rock which overlie the granite foundation? [1]The name given by Sir Roderick Murchison to a vast series of fossiliferous strata, which lies between the non-fossiliferous slaty schists below and the old red sandstone above. The system is well developed in the region of Shropshire, etc., once inhabited by the Silures under Caractacus, or Caradoc. (Tr.) If I am right, I thought, I must soon find some fossil remains of primitive life; and then we must yield to evidence. I will look. I had not gone a hundred paces before incontestable proofs presented themselves. It could not be otherwise, for in the Silurian age the seas contained at least fifteen hundred vegetable and animal species. My feet, which had become accustomed to the indurated lava floor, suddenly rested upon a dust composed of the _debris_ of plants and shells. In the walls were distinct impressions of fucoids and lycopodites. Professor Liedenbrock could not be mistaken, I thought, and yet he pushed on, with, I suppose, his eyes resolutely shut. This was only invincible obstinacy. I could hold out no longer. I picked up a perfectly formed shell, which had belonged to an animal not unlike the woodlouse: then, joining my uncle, I said: "Look at this!" "Very well," said he quietly, "it is the shell of a crustacean, of an extinct species called a trilobite. Nothing more." "But don't you conclude--?" "Just what you conclude yourself. Yes; I do, perfectly. We have left the granite and the lava. It is possible that I may be mistaken. But I cannot be sure of that until I have reached the very end of this gallery." "You are right in doing this, my uncle, and I should quite approve of your determination, if there were not a danger threatening us nearer and nearer." "What danger?" "The want of water." "Well, Axel, we will put ourselves upon rations." CHAPTER XX. THE FIRST SIGNS OF DISTRESS