"Be quite at rest on that point; there is no danger of their breaking through. But to return to our calculations. We are to the southeast, two hundred and fifty miles from the base of Sneffels, and, according to my preceding notes, I think we have gone sixteen leagues in a downward direction."

"Sixteen leagues--fifty miles!" I cried.

"I am sure of it."

"But that is the extreme limit allowed by science for the thickness of the earth's crust," I replied, referring to my geological studies.

"I do not contravene that a.s.sertion," was his quiet answer.

"And at this stage of our journey, according to all known laws on the increase of heat, there should be here a temperature of fifteen hundred degrees of Reaumur."

"There should be--you say, my boy."

"In which case this granite would not exist, but be in a state of fusion."

"But you perceive, my boy, that it is not so, and that facts, as usual, are very stubborn things, overruling all theories."

"I am forced to yield to the evidence of my senses, but I am nevertheless very much surprised."

"What heat does the thermometer really indicate?" continued the philosopher.

"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 lat.i.tude 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 circ.u.mference 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 pa.s.sage does not take us direct to the end we require? Moreover, I have in my favor, fortunately, a precedent. What I have undertaken to do, another has done, and he having succeeded, why should I not be equally successful?"

"I hope, indeed, you will, but still, I suppose I may be allowed to--"

"You are allowed to hold your tongue," cried Professor Hardwigg, "when you talk so unreasonably as this."

I saw at once that the old doctorial Professor was still alive in my uncle--and fearful to rouse his angry pa.s.sions, I dropped the unpleasant subject.

"Now, then," he explained, "consult the manometer. What does that indicate?"

"A considerable amount of pressure."

"Very good. You see, then, that by descending slowly, and by gradually accustoming ourselves to the density of this lower atmosphere, we shall not suffer."

"Well, I suppose not, except it may be a certain amount of pain in the ears," was my rather grim reply.

"That, my dear boy, is nothing, and you will easily get rid of that source of discomfort by bringing the exterior air in communication with the air contained in your lungs."

"Perfectly," said I, for I had quite made up my mind in no wise to contradict my uncle. "I should fancy almost that I should experience a certain amount of satisfaction in making a plunge into this dense atmosphere. Have you taken note of how wonderfully sound is propagated?"

"Of course I have. There can be no doubt that a journey into the interior of the earth would be an excellent cure for deafness."

"But then, Uncle," I ventured mildly to observe, "this density will continue to increase."

"Yes--according to a law which, however, is scarcely defined. It is true that the intensity of weight will diminish just in proportion to the depth to which we go. You know very well that it is on the surface of the earth that its action is most powerfully felt, while on the contrary, in the very centre of the earth bodies cease to have any weight at all."

"I know that is the case, but as we progress will not the atmosphere finally a.s.sume the density of water?"

"I know it; when placed under the pressure of seven hundred and ten atmospheres," cried my uncle with imperturbable gravity.

"And when we are still lower down?" I asked with natural anxiety.

"Well, lower down, the density will become even greater."

"Then how shall we be able to make our way through this atmospheric fog?"

"Well, my worthy nephew, we must ballast ourselves by filling our pockets with stones," said Professor Hardwigg.

"Faith, Uncle, you have an answer for everything," was my only reply.

I began to feel that it was unwise of me to go any farther into the wide field of hypotheses for I should certainly have revived some difficulty, or rather impossibility, that would have enraged the Professor.