Man's constitution is so peculiar that his health is purely a negative matter. No sooner is the rage of hunger appeased than it becomes difficult to comprehend the meaning of starvation. It is only when you suffer that you really understand.  
As to anyone who has not endured privation having any notion of the matter, it is simply absurd.
 
With us, after a long fast, some mouthfuls of bread and meat, a little moldy biscuit and salt beef triumphed over all our previous gloomy and saturnine thoughts.
 
Nevertheless, after this repast each gave way to his own reflections. I wondered what were those of Hans—the man of the extreme north, who was yet gifted with the fatalistic resignation of Oriental character. But the utmost stretch of the imagination would not allow me to realize the truth. As for my individual self, my thoughts had ceased to be anything but memories of the past, and were all connected with that upper world which I never should have left. I saw it all now, the beautiful house in the Konigstrasse, my poor Gretchen, the good Martha; they all passed before my mind like visions of the past. Every time any of the lugubrious groanings which were to be distinguished in the hollows around fell upon my ears, I fancied I heard the distant murmur of the great cities above my head.
 
As for my uncle, always thinking of his science, he examined the nature of the shaft by means of a torch. He closely examined the different strata one above the other, in order to recognize his situation by geological theory. This calculation, or rather this estimation, could by no means be anything but approximate. But a learned man, a philosopher, is nothing if not a philosopher, when he keeps his ideas calm and collected; and certainly the Professor possessed this quality to perfection.
 
I heard him, as I sat in silence, murmuring words of geological science. As I understood his object and his meaning, I could not but interest myself despite my preoccupation in that terrible hour.
 
"Eruptive granite," he said to himself, "we are still in the primitive epoch. But we are going up—going up, still going up. But who knows? Who knows?"
 
Then he still hoped. He felt along the vertical sides of the shaft with his hand, and some few minutes later, he would go on again in the following style:
 
"This is gneiss. This is mica schist—siliceous mineral. Good again; this is the epoch of transition, at all events, we are close to them—and then, and then—"
 
What could the Professor mean? Could he, by any conceivable means, measure the thickness of the crust of the earth suspended above our heads? Did he possess any possible means of making any approximation to this calculation? No.
 
The manometer was wanting, and no summary estimation could take the place of it.
 
And yet, as we progressed, the temperature increased in the most extraordinary degree, and I began to feel as if I were bathed in a hot and burning atmosphere. Never before had I felt anything like it. I could only compare it to the hot vapor from an iron foundry, when the liquid iron is in a state of ebullition and runs over. By degrees, and one after the other, Hans, my uncle, and myself had taken off our coats and waistcoats. They were unbearable. Even the slightest garment was not only uncomfortable, but the cause of extreme suffering.
 
"Are we ascending to a living fire?" I cried; when, to my horror and astonishment, the heat became greater than before.
 
"No, no," said my uncle, "it is simply impossible, quite impossible."
 
"And yet," said I, touching the side of the shaft with my naked hand, "this wall is literally burning."
 
At this moment, feeling as I did that the sides of this extraordinary wall were red hot, I plunged my hands into the water to cool them. I drew them back with a cry of despair.
 
"The water is boiling!" I cried.
 
My uncle, the Professor, made no reply other than a gesture of rage and despair.
 
Something very like the truth had probably struck his imagination.
 
But I could take no share in either what was going on, or in his speculations. An invincible dread had taken possession of my brain and soul. I could only look forward to an immediate catastrophe, such a catastrophe as not even the most vivid imagination could have thought of. An idea, at first vague and uncertain, was gradually being changed into certainty.
 
I tremulously rejected it at first, but it forced itself upon me by degrees with extreme obstinacy. It was so terrible an idea that I scarcely dared to whisper it to myself.
 
And yet all the while certain, and as it were, involuntary observations determined my convictions. By the doubtful glare of the torch, I could make out some singular changes in the granitic strata; a strange and terrible phenomenon was about to be produced, in which electricity played a part.
 
Then this boiling water, this terrible and excessive heat? I determined as a last resource to examine the compass.
 
The compass had gone mad!
 
Yes, wholly stark staring mad. The needle jumped from pole to pole with sudden and surprising jerks, ran round, or as it is said, boxed the compass, and then ran suddenly back again as if it had the vertigo.
 
I was aware that, according to the best acknowledged theories, it was a received notion that the mineral crust of the globe is never, and never has been, in a state of complete repose.
 
It is perpetually undergoing the modifications caused by the decomposition of internal matter, the agitation consequent on the flowing of extensive liquid currents, the excessive action of magnetism which tends to shake it incessantly, at a time when even the multitudinous beings on its surface do not suspect the seething process to be going on.
 
Still this phenomenon would not have alarmed me alone; it would not have aroused in my mind a terrible, an awful idea.
 
But other facts could not allow my self-delusion to last.
 
Terrible detonations, like Heaven's artillery, began to multiply themselves with fearful intensity. I could only compare them with the noise made by hundreds of heavily laden chariots being madly driven over a stone pavement. It was a continuous roll of heavy thunder.
 
And then the mad compass, shaken by the wild electric phenomena, confirmed me in my rapidly formed opinion. The mineral crust was about to burst, the heavy granite masses were about to rejoin, the fissure was about to close, the void was about to be filled up, and we poor atoms to be crushed in its awful embrace!
 
"Uncle, Uncle!" I cried, "we are wholly, irretrievably lost!"
 
"What, then, my young friend, is your new cause of terror and alarm?" he said in his calmest manner. "What fear you now?"
 
"What do I fear now!" I cried in fierce and angry tones. "Do you not see that the walls of the shaft are in motion? Do you not see that the solid granite masses are cracking? Do you not feel the terrible, torrid heat? Do you not observe the awful boiling water on which we float? Do you not remark this mad needle? Every sign and portent of an awful earthquake!"
 
My uncle coolly shook his head.
 
"An earthquake," he replied in the most calm and provoking tone.
 
"Yes."
 
"My nephew, I tell you that you are utterly mistaken," he continued.
 
"Do you not, can you not, recognize all the well-known symtons—"
 
"Of an earthquake? By no means. I am expecting something far more important."
 
"My brain is strained beyond endurance—what, what do you mean?" I cried.
 
"An eruption, Harry."
 
"An eruption," I gasped. "We are, then, in the volcanic shaft of a crater in full action and vigor."
 
"I have every reason to think so," said the Professor in a smiling tone, "and I beg to tell you that it is the most fortunate thing that could happen to us."
 
The most fortunate thing! Had my uncle really and truly gone mad? What did he mean by these awful words—what did he mean by this terrible calm, this solemn smile?
 
"What!" cried I, in the height of my exasperation, "we are on the way to an eruption, are we? Fatality has cast us into a well of burning and boiling lava, of rocks on fire, of boiling water, in a word, filled with every kind of eruptive matter? We are about to be expelled, thrown up, vomited, spit out of the interior of the earth, in common with huge blocks of granite, with showers of cinders and scoriae, in a wild whirlwind of flame, and you say—the most fortunate thing which could happen to us."
 
"Yes," replied the Professor, looking at me calmly from under his spectacles, "it is the only chance which remains to us of ever escaping from the interior of the earth to the light of day."
 
It is quite impossible that I can put on paper the thousand strange, wild thoughts which followed this............