“Look outside!” cried Johnston. The water was now still, but it was gradually rising up the sides of the boat, and in a moment it had closed over the crystal roof. Both of the captives were conscious of a heavy sensation in the head and a dull roaring in the ears. Down they went, at first slowly and then more rapidly, till it seemed to them that they had descended over a thousand feet. Great monsters like whales swam to the vessel, as if attracted by the lights, and their massive bodies jarred against the glass walls as they turned to swim away. They sank about five hundred feet lower; and all at once the lights went out, and the boat gradually stopped. It was at once so dark that the two captives could not see each other, though only the width of the table separated them. Everything was profoundly still; not a sound came from the men in the other rooms. Presently Thorndyke whispered, “Look, do you see that red light overhead?” “Yes,” said Johnston, “it looks like a star.” “It is our bonfire,” said Thorndyke, “that's what betrayed us.” Again the vessel began to sink, and more rapidly than ever; indeed, as Thorndyke expressed it, he had the cool feeling that nervous people experience in going down quickly in an elevator. “If we go any lower,” he added, as the great rubber hull seemed to struggle like some living monster, “the sides of this thing will collapse like an egg-shell and we will be as flat as pancakes.” “You need not fear, we have much lower to go!” It was the captain's voice, but they could not tell from whence it came. Then they heard again the seductive music, and it was so soothing that they soon fell asleep. They had no idea how long they had slept, but they were awakened by the ringing of a bell and felt the vessel was coming to a stop. They were still far beneath the surface; indeed, the boat was resting on the bottom, for in the light of two or three powerful search-lights they saw a wide succession of submerged hills, vales, and rugged cliffs. Before them was a great mountain-side and in it they saw the mouth of a dark tunnel. They had scarcely noticed it before the vessel rose a little and glided toward the tunnel and entered it. Through the glass walls they could see that it was narrow, and that the ragged sides and roof were barely far enough apart to admit them. Suddenly one of the men came in and drew a curtain down behind them, and, with a vexed look on his face retired. When he was gone Johnston put his lips close to Thorndyke's ear and whispered: “Did you see that?” “See what?” “Just as he drew the curtain down I saw what looked to me like a cliff of solid gold. It had been dug out into a cavern in which I saw a vessel like this, and men in diving suits digging and loading it.” This took the Englishman's breath away for a moment, then he remarked: “That accounts for the heel-tap we found; who knows, these people may be possessors of the richest gold and silver mines on earth.”