"Well, said the Professor, with the most imperturbable tranquillity, "it is the shell of a crustaceous animal of the extinct order of the trilobites; nothing more, I assure you." "But," cried I, much troubled at his coolness, "do you draw no conclusion from it?" "Well, if I may ask, what conclusion do you draw from it yourself?" "Well, I thought--" "I know, my boy, what you would say, and you are right, perfectly and incontestably right. We have finally abandoned the crust of lava and the road by which the lava ascended. It is quite possible that I may have been mistaken, but I shall be unable to discover my error until I get to the end of this gallery." "You are quite right as far as that is concerned," I replied, "and I should highly approve of your decision, if we had not to fear the greatest of all dangers." "And what is that?" "Want of water." "Well, my dear Henry, it can't be helped. We must put ourselves on rations." And on he went. CHAPTER 17 DEEPER AND DEEPER--THE COAL MINE In truth, we were compelled to put ourselves upon rations. Our supply would certainly last not more than three days. I found this out about supper time. The worst part of the matter was that, in what is called the transition rocks, it was hardly to be expected we should meet with water! I had read of the horrors of thirst, and I knew that where we were, a brief trial of its sufferings would put an end to our adventures--and our lives! But it was utterly useless to discuss the matter with my uncle. He would have answered by some axiom from Plato. During the whole of next day we proceeded on our journey through this interminable gallery, arch after arch, tunnel after tunnel. We journeyed without exchanging a word. We had become as mute and reticent as Hans, our guide. The road had no longer an upward tendency; at all events, if it had, it was not to be made out very clearly. Sometimes there could be no doubt that we were going downwards. But this inclination was scarcely to be distinguished, and was by no means reassuring to the Professor, because the character of the strata was in no wise modified, and the transition character of the rocks became more and more marked. It was a glorious sight to see how the electric light brought out the sparkles in the walls of the calcareous rocks, and the old red sandstone. One might have fancied oneself in one of those deep cuttings in Devonshire, which have given their name to this kind of soil. Some magnificent specimens of marble projected from the sides of the gallery: some of an agate grey with white veins of variegated character, others of a yellow spotted color, with red veins; farther off might be seen samples of color in which cherry-tinted seams were to be found in all their brightest shades.