“Yes; it is perfectly well known that the internal temperature rises one degree for every 70 feet in depth; now, admitting this proportion to be constant, and the radius of the earth being fifteen hundred leagues, there must be a temperature of 360,032 degrees at the centre of the earth. Therefore, all the substances that compose the body of this earth must exist there in a state of incandescent gas; for the metals that most resist the action of heat, gold, and platinum, and the hardest rocks, can never be either solid or liquid under such a temperature. I have therefore good reason for asking if it is possible to penetrate through such a medium.”

“So, Axel, it is the heat that troubles you?”

“Of course it is. Were we to reach a depth of thirty miles we should have arrived at the limit of the terrestrial crust, for there the temperature will be more than 2,372 degrees.”

“Are you afraid of being put into a state of fusion?”