returning, if he ever went, I say no--he never, never did that."

"Now for your reason?" said my uncle ironically.

"All the theories of science demonstrate such a feat to be
impracticable."

"The theories say that, do they?" replied the Professor in the tone
of a meek disciple. "Oh! unpleasant theories! How the theories will
hinder. us, won't they?"

I saw that he was only laughing at me; but I went on all the same.

"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 2372 degrees."