My uncle now began to see to the efficiency of our Ruhmkorff coil, which would doubtless soon be needed; the raft, securely fastened to a rock, was left alone. Moreover, the opening into the new gallery was not twenty paces distant from the spot. Our little troop, with myself at the head, advanced.
The orifice, which was almost circular, presented a diameter of about five feet; the somber tunnel was cut in the living rock, and coated on the inside by the different material which had once passed through it in a state of fusion. The lower part was about level with the water, so that we were able to penetrate to the interior without difficulty.
We followed an almost horizontal direction; when, at the end of about a dozen paces, our further advance was checked by the interposition of an enor
