"We need," continued Ivan, "an apparatus which is a combination of the diver's and the fireman's dress. To the glass helmet, which will be attached to the coat-collar by means of air-proof caoutchouc, there will be fastened two tubes, through one of which the necessary amount of air will be conveyed to us, and through the other the bad air will be expelled. The ends of both the tubes will remain here, while we drag them after us in the same manner as does the diver. Although all bad air escapes from our helmets, still we shall find the air rather warmer than it is up here, and it will smell like vulcanized india-rubber; still we cannot suffocate. To this third aperture an elastic tube will be fixed, which unites both helmets; through this tube each will hear what the other says, for the glass is so thick that no sound penetrates it, and when you have it on your head you will with difficulty hear what is said by me."
Spitzhase had begun to feel very uncomfortable, for now the miner proceeded to adjust the glass helmet to his head. When the tubes were being fixed into the three apertures he perceived that he had become suddenly stone deaf. He saw the lips of the two commissioners moving, but not one word could he hear. He no longer belonged to the world. Only one sound reached him, and that was the voice of the man to whose head he was fastened.
"Take one end of the hose upon your arm," shouted the voice into his helmet; yet the sound seemed to come from a long way off, or as if out of a tunnel.
Mechanically he took the coil on his shoulder.
"Let us go," shouted Ivan, taking the other end of the coil on his shoulder, and, opening a thick oak door, which had hitherto escaped Spitzhase's observation, they passed through.
The two commissioners had heard nothing that had passed between the two "knights"; but when they saw the oak door open they hurriedly asked the miners whether the foul air did not come in. The older workman reassured them; the carbon was much heavier than oxygen, and even thicker than hydrogen. The foul air remained below, where the two divers had gone. They might have every confidence so long as the safety-lamps burned. Meantime, the others had penetrated into a roomy cavern, the walls of which proved it had not been made by the hands of men, but was a natural formation. Each partition of the wall fitted into another, like the blocks of a puzzle, and each block was as smooth as a steel mirror. They were masses of coal set obliquely one upon another. The cavern was bridged over with thick, strong wooden planks. The gearing strap, which had made its way from the cavern in serpent-like fashion, had set a wheel in motion, and the noise of the clapper resounded under the bridge, and made a sound as if it were working in deep water. From this bridge a narrow path led obliquely into the stone layers. Once beyond the entrance into this dark path the lamps ceased to burn; the coal-gas had begun its sway. Upon the bridge an electric machine was placed, whose brilliant light was shaded by a wire screen.
The old miner set the machine working, and the light flashed into every nook and cranny of the subterranean cavern. It lighted up the narrow tunnel which, for the last month, Ivan had been boring from his own mine to that of his neighbor. He had told no one what he had been doing, but now the work was almost finished; it only required to be broken through. This work, which would take another week to complete, needed to be done in a diver's equipment. The length of the narrow tunnel was perfectly illumined by the electric machine, as if in the broad light of the sun. Where it turned out of its course high looking-glasses of polished steel were placed in positions which reflected the light itself until it faded away to a faint glimmer. The two divers could now hardly discern an object.
"We shall soon be in darkness," said Spitzhase to Ivan.
"We shall have light enough," returned Ivan; and he led the way farther into the tunnel.
Spitzhase was forced to follow, for his head was fastened to Ivan's head. Wonderful pair of Siamese twins! If the pipe that bound them together were to break, both were dead men.