Twenty-seven six-tenths."

"So that science is wrong by fourteen hundred and seventy-four degrees
and four-tenths. According to which, it is demonstrated that the
proportional increase in temperature is an exploded error. Humphry Davy
here shines forth in all his glory. He is right, and I have acted wisely
to believe him. Have you any answer to make to this statement?"

Had I chosen to have spoken, I might have said a great deal. I in no way
admitted the theory of Humphry Davy--I still held out for the theory of
proportional increase of heat, though I did not feel it.

I was far more willing to allow that this chimney of an extinct volcano
was covered by lava of a kind refractory to heat--in fact a bad
conductor--which did not allow the great increase of temperature to
percolate through its sides. The hot water jet supported my view of the
matter.

But without entering on a long and useless discussion, or seeking for
new arguments to controvert my uncle, I contented myself with taking up
facts as they were.

"Well, sir, I take for granted that all your calculations are correct,
but allow me to draw from them a rigorous and definite conclusion."

"Go on, my boy--have your say," cried my uncle goodhumoredly.

"At the place where we now are, under the latitude of Iceland, the
terrestrial depth is about fifteen hundred and eighty-three leagues."

"Fifteen hundred eighty-three and a quarter."

"Well, suppose we say sixteen hundred in round numbers. Now, out of a
voyage of sixteen hundred leagues we have completed sixteen."

"As you say, what then?"

"At the expense of a diagonal journey of no less than eighty-five
leagues."

"Exactly."

"We have been twenty days about it."

"Exactly twenty days."

"Now sixteen is the hundredth part of our contemplated expedition. If we
go on in this way we shall be two thousand days, that is about five
years and a half, going down."

The Professor folded his arms, listened, but did not speak.

"Without counting that if a vertical descent of sixteen leagues costs us
a horizontal of eighty-five, we shall have to go about eight thousand
leagues to the southeast, and we must therefore come out somewhere in
the circumference long before we can hope to reach the centre."

"Bother your calculations," cried my uncle in one of his old rages. "On
what basis do they rest? How do you know that this passage does not take
us direct to the end we require? Moreover, I have in my favor,