Jules Verne

“ Hans sat down at once. The lamps were hung upon a projection in the lava; we were in a sort of cavern where there was plenty of air. Certain puffs of air reached us. What atmospheric disturbance was the cause of them? I could not answer that question at the moment. Hunger and fatigue made me incapable of reasoning. A descent of seven hours consecutively is not made without considerable expenditure of strength. I was exhausted. The order to 'halt' therefore gave me pleasure. Hans laid our provisions upon a block of lava, and we ate with a good appetite. ”

“ Moreover, in the neighbourhood of an extinct volcano, through gneiss, it has been observed that the increase of a degree is only attained at every 125 feet. Let us therefore assume this last hypothesis as the most suitable to our situation, and calculate."
"Well, do calculate, my boy."
"Nothing is easier," said I, putting down figures in my note book. "Nine times a hundred and twenty-five feet gives a depth of eleven hundred and twenty-five feet." ”

“ The only difficulty in proceeding lay in not sliding too fast down an incline of about forty-five degrees; happily certain asperities and a few blisterings here and there formed steps, and we descended, letting our baggage slip before us from the end of a long rope.
But that which formed steps under our feet became stalactites overhead. The lava, which was porous in many places, had formed a surface covered with small rounded blisters ”