XVIII

XVIII

AT EIGHT IN THE morning a ray of daylight came to wake us up. The thousand facets of lava on the walls received it on its passage, and scattered it like a shower of sparks.

There was light enough to distinguish surrounding objects.

“Well, Axel, what do you say?” exclaimed my uncle, rubbing his hands. “Did you ever spend a quieter night in our little house in the Königstrasse? No noise of carts, no cries of merchants, no boatmen vociferating!”

“No doubt it’s very quiet at the bottom of this well, but there’s something alarming in the quietness itself.”

“Now come!” my uncle exclaimed; “if you’re frightened already, what will you be later on? We’ve not gone a single inch yet into the bowels of the earth.”

“What do you mean?”

“I mean that we’ve only reached the ground level of the island. This long vertical tube, which terminates at the mouth of the crater, has its lower end at about sea level.”

“Are you sure of that?”

“Quite sure. Check the barometer.”

In fact, the mercury, which had gradually risen in the instrument as we descended, had stopped at twenty-nine inches.

“You see,” said the professor, “we only have a pressure of one atmosphere, and can’t wait for the manometer to take the place of the barometer.”

And indeed, this instrument would become useless as soon as the weight of the atmosphere exceeded the pressure at sea level.

“But,” I said, “isn’t there reason to fear that this steadily increasing pressure will become very painful?”

“No; we’ll descend at a slow pace, and our lungs will become used to breathing a denser atmosphere. Aeronauts lack air as they rise to high elevations, and we’ll perhaps have too much. But I prefer that. Let’s not waste a moment. Where’s the packet we sent down before us?”

I then remembered that we had searched for it in vain the evening before. My uncle questioned Hans who, after having looked around attentively with his hunter’s eyes, replied:

“Der huppe!”

“Up there.”

And so it was. The bundle had been caught by a projection a hundred feet above us. Immediately the agile Icelander climbed up like a cat, and in a few minutes the package was in our possession.

“Now,” said my uncle, “let’s have breakfast, but let’s have it like people who may have a long route in front of them.”

The biscuit and extract of meat were washed down with a draught of water mingled with a little gin.

Breakfast over, my uncle drew from his pocket a small notebook, intended for scientific observations. He consulted his instruments, and recorded:

Monday, July 1Chronometer: 8.17 a.m. Barometer: 29 7/12”. Thermometer: 6°C. Direction: E.S.E.

This last observation applied to the dark tunnel, and was indicated by the compass.

“Now, Axel,” exclaimed the professor with enthusiasm, “we’re really going into the bowels of the globe. At this precise moment the journey begins.”

That said, my uncle took the Ruhmkorff device that was hanging from his neck with one hand; and with the other he connected the electric current with the coil in the lantern, and a rather bright light dispersed the darkness of the passage.

Hans carried the other device, which was also turned on. This ingenious electrical appliance would enable us to go on for a long time by creating an artificial light even in the midst of the most inflammable gases.

“Let’s go!” exclaimed my uncle.

Each of us took his package. Hans pushed the load of cords and clothes before; and, myself going last, we entered the tunnel.

At the moment of penetrating into this dark tunnel, I raised my head, and saw for the last time through the length of that vast tube the sky of Iceland, “which I was never to behold again.”

The lava, in the last eruption of 1229, had forced a passage through this tunnel. It still lined the walls with a thick and glistening coat. The electric light was here intensified a hundredfold by reflection.

The only difficulty in advancing lay in not sliding too fast down an incline of about forty-five degrees; fortunately certain abrasions and a few blisters here and there formed steps, and we descended, letting our baggage slip before us from the end of a long rope.

But what made steps under our feet had turned into stalactites overhead. The lava, porous in some places, had taken the shape of small round blisters; opaque quartz crystals, decorated with limpid drops of glass and suspended like chandeliers from the vaulted roof, seemed to light up at our passage. It seemed as if the spirits of the abyss were illuminating their palace to receive their earthly guests.

“It’s magnificent!” I exclaimed spontaneously. “My uncle, what a sight! Don’t you admire these hues of lava, which blend from reddish brown to bright yellow by imperceptible gradations? And these crystals that seem to us like globes of light?”

“Ah! you’re coming around, Axel!” replied my uncle. “So you find this splendid, my boy! Well, you’ll see many others yet, I hope. Let’s go! Let’s go!”

He had better have said “slide,” for we did nothing but drop down the steep slopes. It was the facilis descensus Averni of Virgil.ao The compass, which I consulted frequently, gave our direction as southeast with inflexible steadiness. This lava stream deviated neither to the right nor to the left.

Yet there was no sensible increase in temperature. This justified Davy’s theory, and more than once I consulted the thermometer with surprise. Two hours after our departure it only showed 10°, an increase of only 4°. This was reason to believe that our descent was more horizontal than vertical. As for the exact depth we had reached, it was very easy to ascertain that; the professor measured the angles of deviation and inclination accurately on the road, but he kept the results of his observations to himself.

At about eight in the evening he signaled to stop. Hans sat down at once. The lamps were hung on a projection in the lava; we were in a sort of cavern where there was no lack of air. On the contrary. Certain breezes reached us. What caused them? That was a question I did not try to answer at the moment. Hunger and exhaustion made me incapable of reasoning. A descent of seven consecutive hours is not accomplished without considerable expenditure of strength. I was exhausted. The word ‘stop’ therefore gave me pleasure. Hans spread some provisions out on a block of lava, and we ate with a good appetite. But one thing troubled me; our supply of water was half consumed. My uncle counted on a fresh supply from underground sources, but so there had been none. I could not help drawing his attention to this issue.

“Are you surprised at this lack of springs?” he said.

“More than that, I’m anxious about it; we have only water enough for five days.”

“Don’t worry, Axel, I guarantee you that we’ll find water, and more than we’ll want.”

“When?”

“When we have left this layer of lava behind us. How can springs break through such walls as these?”

“But perhaps this passage runs to a very great depth. It seems to me that we’ve not yet made much progress vertically.”

“Why do you suppose that?”

“Because if we had advanced far into the crust of earth, it would be hotter.”

“According to your theory,” said my uncle. “What does the thermometer say?”

“Hardly 15°C, which means an increase of only 9° since our departure.”

“So, draw your conclusion.”

“This is my conclusion. According to exact observations, the temperature in the interior of the globe increases at the rate of 1° Celsius for every hundred feet. But certain local conditions may modify this rate. For example, at Yakutsk in Siberia it’s been observed that the increase of 1° takes place every 36 feet. This difference clearly depends on the heat-conducting power of the rocks. Moreover, in the neighborhood of an extinct volcano, through gneiss, it’s been observed that the increase of 1° is only attained every 125 feet. Let’s therefore assume this last hypothesis as the most appropriate for our situation, and calculate.”

“Do calculate, my boy.”

“Nothing’s easier,” I said, putting down figures in my notebook. “Nine times a hundred and twenty-five feet adds up to a depth of eleven hundred and twenty-five feet.”

“Very accurate indeed.”

“Well?”

“By my observation we are 10,000 feet below sea level.”

“Is that possible?”

“Yes, or numbers aren’t numbers anymore!”

The professor’s calculations were accurate. We had already reached a depth of six thousand feet beyond that so far reached by the foot of man, such as the mines of Kitzbühl in Tyrol, and those of Wuttemberg in Bohemia.

The temperature, which should have been 81°C in this place, was scarcely 15°. This was serious cause for reflection.