"What is this?" I asked, shaken by this sudden stoppage as if by a shock. "It is a halt," replied my uncle. "Is the eruption checked?" I asked. "I hope not." I rose, and tried to look around me. Perhaps the raft itself, stopped in its course by a projection, was staying the volcanic torrent. If this were the case we should have to release it as soon as possible. But it was not so. The blast of ashes, scorix, and rubbish had ceased to rise. "Has the eruption stopped?" I cried. "Ah!" said my uncle between his clenched teeth, "you are afraid. But don't alarm yourself--this lull cannot last long. It has lasted now five minutes, and in a short time we shall resume our journey to the mouth of the crater." As he spoke, the Professor continued to consult his chronometer, and he was again right in his prognostications. The raft was soon hurried and driven forward with a rapid but irregular movement, which lasted about ten minutes, and then stopped again. "Very good," said my uncle; "in ten minutes more we shall be off again, for our present business lies with an intermittent volcano. It gives us time now and then to take breath." This was perfectly true. When the ten minutes were over we started off again with renewed and increased speed. We were obliged to lay fast hold of the planks of the raft, not to be thrown off. Then again the paroxysm was over. I have since reflected upon this singular phenomenon without being able to explain it. At any rate it was clear that we were not in the main shaft of the volcano, but in a lateral gallery where there were felt recurrent tunes of reaction. How often this operation was repeated I cannot say. All I know is, that at each fresh impulse we were hurled forward with a greatly increased force, and we seemed as if we were mere projectiles. During the short halts we were stifled with the heat; whilst we were being projected forward the hot air almost stopped my breath. I thought for a moment how delightful it would be to find myself carried suddenly into the arctic regions, with a cold 30° below the freezing point. My overheated brain conjured up visions of white plains of cool snow, where I might roll and allay my feverish heat. Little by little my brain, weakened by so many constantly repeated shocks, seemed to be giving way altogether. But for the strong arm of Hans I should more than once have had my head broken against the granite roof of our burning dungeon.