"Scarcely fifteen degrees by Reaumur, which is only an increase of nine since our departure."
"Well, and what conclusion does that bring you to?" inquired the Professor.
"The deduction I draw from this is very simple. According to the most exact observations, the augmentation of the temperature of the interior of the earth is one degree for every hundred feet. But certain local causes may considerably modify this figure. Thus at Yakoust in Siberia, it has been remarked that the heat increases a degree every thirty-six feet. The difference evidently depends on the conductibility of certain rocks. In the neighborhood of an extinct volcano, it has been remarked that the elevation of temperature was only one degree in every five-and-twenty feet. Let us, then, go upon this calculation—which is the most favorable—and calculate."
"Calculate away, my boy."
"Nothing easier," said I, pulling out my notebook and pencil. "Nine times one hundred and twenty-five feet make a depth of eleven hundred and twenty-five feet."
"Archimedes could not have spoken more geometrically."
"Well?"
"Well, according to my observations, we are at least ten thousand feet below the level of the sea."
"Can it be possible?"
"Either my calculation is correct, or there is no truth in figures."