"It is really wonderful," he said, "that you should go in and out of such a place without stumbling."
"I have lived all my life in these places, and know them as well as my own home. Here it is very cold; wrap yourself up if have you a cloak with you. We shall soon be out at the other end." He walked on, feeling his way with his hand along the wall, which was formed of upright beams, and saying:
"Mind you do not stumble over the ruts in the path; they bring the mineral along here from the diggings above. Are you cold?"
"Tell me," said the doctor, gaily. "Are you quite certain that the earth has not swallowed us up? This passage is the gullet of some monstrous insectivorous brute into whose stomach we miserable worms have inadvertently crept.—Do you often take a walk in this delectable spot?"
"Yes, often, and at all hours, and I think the place delightful. Now we are in the most arid part—the ground here is pure sand—now we are on the stones again. Here there is a constant drip of sulphurous water, and down there we have a block of rock in which there are petrified shells. There are layers of slate over there. Do you hear that toad croaking? we are near the opening now; the rascal sits there every night; I know him quite well. He has a hoarse, slow voice."
"Who—the toad?"
"Yes, Señor; we are near the end now."
"So I see; it looks like an eye staring at us—that is the mouth of the corridor."
No sooner were they out in the air again, than the first thing that struck the doctor's ear was the same melancholy song as he had heard before. The blind boy heard it too; he turned round to his companion and said, smiling with pride and pleasure: