Could there possibly have been a more exact guide? As soon as we have arrived at the summit of Snæfell we shall have no hesitation as to the proper road to take."
Decidedly, my uncle had answered every one of my objections. I saw that his position on the old parchment was impregnable. I therefore ceased to press him upon that part of the subject, and as above all things he must be convinced, I passed on to scientific objections, which in my opinion were far more serious.
"Well, then," I said, "I am forced to admit that Saknussemm's sentence is clear, and leaves no room for doubt. I will even allow that the document bears every mark and evidence of authenticity. That learned philosopher did get to the bottom of Sneffels, he has seen the shadow of Scartaris touch the edge of the crater before the kalends of July; he may even have heard the legendary stories told in his day about that crater reaching to the centre of the world; but as for reaching it himself, as for performing the journey, and 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."
"Are you afraid of being put into a state of fusion?"
"I will leave you to decide that question," I answered rather sullenly. "This is my decision," replied Professor Liedenbrock, putting on one of his grandest airs. "Neither you nor anybody else knows with any certainty what is going on in the interior of this globe, since not the twelve thousandth part of its radius is known; science is eminently perfectible; and every new theory is soon routed by a newer. Was it not always believed until Fourier that the temperature of the interplanetary spaces decreased perpetually? and is it not known at the present time that the greatest cold of the ethereal regions is never lower than 40 degrees below zero Fahr.? Why should it not be the same with the internal heat? Why should it not, at a certain depth, attain an impassable limit, instead of rising to such a point as to fuse the most infusible metals?"
As my uncle was now taking his stand upon hypotheses, of course, there was nothing to be said.
"Well, I will tell you that true savants, amongst them Poisson, have demonstrated that if a heat of 360,000 degrees  existed in the interior of the globe, the fiery gases arising from the fused matter would acquire an elastic force which the crust of the earth would be unable to resist, and that it would explode like the plates of a bursting boiler."
"That is Poisson's opinion, my uncle, nothing more."
"Granted. But it is likewise the creed adopted by other distinguished geologists, that the interior of the globe is neither gas nor water, nor any of the heaviest minerals known, for in none of these cases would the earth weigh what it does."
"Oh, with figures you may prove anything!"
"But is it the same with facts! Is it not known that the number of volcanoes has diminished since the first days of creation? and if there is central heat may we not thence conclude that it is in process of diminution?"
"My good uncle, if you will enter into the legion of speculation, I can discuss the matter no longer."
"But I have to tell you that the highest names have come to the support of my views.