o 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 ma