What did the Professor mean? Could he be trying to measure the thickness of the crust of the earth that lay between us and the world above? Had he any means of making this calculation? No, he had not the aneroid, and no guessing could supply its place.

Still the temperature kept rising, and I felt myself steeped in a broiling atmosphere. I could only compare it to the heat of a furnace at the moment when the molten metal is running into the mould. Gradually we had been obliged to throw aside our coats and waistcoats, the lightest covering became uncomfortable and even painful.

“Are we rising into a fiery furnace?” I cried at one moment when the heat was redoubling.

“No,” replied my uncle, “that is impossible⁠—quite impossible!”

“Yet,” I answered, feeling the wall, “this well is burning hot.”

At the same moment, touching the water, I had to withdraw my hand in haste.