At eight the next morning, a weak light slowly woke us. The countless crystals in the lava caught what little light there was and scattered it around us like thousands of tiny sparks.
We could finally see the rocks and walls around us.
“Well, Harry, my boy,” Professor Lidenbrock said cheerfully, rubbing his hands. “What do you think now? Have you ever spent such a peaceful night in our house on Königstrasse? No carts rattling past the windows, no street vendors shouting, and no sailors swearing!”
“Uncle, we may be at the bottom of this shaft, but there is something frightening about this silence.”
“Frightening?” he exclaimed. “You are already becoming afraid? What will happen when we go farther? Do you realize that we have not even entered the real interior of the earth yet?”
“What do you mean?”
“We have only reached the ground beneath Iceland. This enormous vertical shaft from the crater of Sneffels ends here, almost exactly at sea level.”
“You are certain?”
“Completely certain. Look at the barometer.”
I checked it. The mercury had risen steadily during our descent, but now it had stopped at twenty-nine inches.
“You see?” my uncle said. “We are still only dealing with ordinary atmospheric pressure. I am curious to see what happens when we replace the barometer with a manometer.”
“But won’t the pressure become dangerous as we go deeper?”
“No. We shall descend slowly, and our lungs will gradually adjust to the heavier air. Aeronauts have gone to great heights where there is hardly any air at all. Why shouldn’t we become accustomed to having more air than usual?”
He looked impatient to continue.
“Now, where is the package that went ahead of us?”
I pointed toward it.
Hans had not noticed it and thought it had become stuck somewhere above us.
“Huppe,” he said.
My uncle laughed.
“First, breakfast. We have a long day’s work ahead of us.”
Our luxurious meal consisted of biscuits and dried meat, washed down with a little water mixed with Schiedam.
When we had finished, my uncle took out his notebook and carefully recorded our position.
Monday, June 29 — 8:17 a.m.
Barometer: 29.6 inches.
Thermometer: 43°F.
Direction: Southeast by east.
He closed the notebook.
“Harry,” he said excitedly, “we are about to take our first real step into the interior of the earth. No human being has ever been here before. From this moment onward, our true journey begins!”
He lifted the Ruhmkorff electrical apparatus hanging around his neck and connected it to the lamp.
A brilliant light suddenly flooded the tunnel.
The effect was astonishing.
Hans switched on his own lamp as well. Thanks to these electrical devices, we could see as clearly as if it were daytime, even though we were surrounded by gases that might easily have caught fire.
“Forward!” my uncle cried.
Hans went first.
My uncle followed.
I came behind them.
Just before entering the dark passage, I looked back through the shaft.
Far above me was the Icelandic sky.
I stared at it for a moment.
Would I ever see the sky again?
The lava that had poured from the earth in 1219 had forced its way through this tunnel and coated the walls with a thick, shining layer. Under the electric light, the whole passage glittered.
But the beauty of the tunnel did not make the journey easy.
The floor sloped steeply downward, and we had to be careful not to slide.
Fortunately, cracks and ridges in the rock gave us places to put our feet. We also tied our heavy luggage to a long rope and let it slide ahead of us.
In some places, the rough lava formed natural steps.
In others, it hung from the ceiling like stalactites.
The lava was full of tiny bubbles, and clear crystals were scattered everywhere. Drops of natural glass hung from the ceiling and flashed in the electric light.
It looked as if we had entered some magical underground palace.
“Magnificent!” I cried. “Uncle, look at these colors! The lava changes gradually from reddish brown to pale yellow. And those crystals look like glowing balls of light!”
“You are beginning to understand the pleasure of travel, Harry,” my uncle replied. “Just wait until we go farther. We have seen almost nothing yet. Come on!”
Actually, “slide on” would have been a better command.
The slope was so smooth that we were almost sliding downward.
Our compass showed that we were traveling southeast. The lava tunnel never turned sharply to either side. It seemed to follow a perfectly straight path.
What surprised me most was that the temperature hardly increased.
This seemed to support Humphry Davy’s theories about the interior of the earth.
Again and again, I checked the thermometer.
Two hours after we started, it showed only 54°F.
That made me think our journey was taking us more horizontally than vertically.
As for our exact depth, my uncle knew how to calculate it. He carefully measured the angles of the tunnel as we moved along, but he kept his results to himself.
At about eight that evening, he finally gave the signal to stop.
Hans sat down immediately.
We hung our lamps from cracks in the lava walls.
We had reached a large cavern.
There was plenty of air here—more than enough.
A steady current of air was even blowing through the cavern.
Where was it coming from?
What underground movement was causing it?
I had no energy left to think about such questions.
We had been walking for seven hours without a real break, and I was completely exhausted.
I was very glad to hear my uncle say one word:
“Halt.”
Hans placed our food on a piece of lava, and we eagerly ate our evening meal.
But there was one serious problem.
Our water supply was already half gone.
My uncle was confident that we would find underground water sooner or later, but so far we had found nothing.
I decided to speak to him about it.
“You’re surprised that we haven’t found a spring?” he asked.
“Of course. I’m worried. We don’t have enough water to last five days.”
“Don’t worry,” he said calmly. “We will find plenty of water—more than we need.”
“When?”
“As soon as we get through this layer of lava.”
“But how can water pass through solid rock?”
“It can’t. That’s exactly why we haven’t found any yet.”
I thought about this for a moment.
“But what if this enormous layer of lava continues all the way to the center of the earth? I don’t think we’ve actually gone very far downward.”
“What makes you think that, Harry?”
“If we had gone very deep below sea level, shouldn’t it be much hotter by now?”
“According to your theory, perhaps. But what does the thermometer tell us?”
“Only about fifteen degrees Réaumur. That’s just nine degrees higher than when we started.”
“And what does that tell you?”
“The answer is simple. According to the usual measurements, the temperature inside the earth rises about one degree for every hundred feet we descend.”
My uncle listened carefully.
“But that rate can change depending on the rocks,” I continued. “In Yakutsk, Siberia, the temperature has been observed to rise one degree every thirty-six feet. Near an extinct volcano, it has risen only one degree every twenty-five feet.”
I opened my notebook.
“So let’s use the most favorable figure and calculate our depth.”
“Go ahead.”
“Easy.”
I wrote the numbers down.
“Nine degrees multiplied by one hundred and twenty-five feet gives us 1,125 feet.”
“Very precise,” my uncle said with a smile.
“Well?”
“Well, according to my measurements, we are at least ten thousand feet below sea level.”
I stared at him.
“That can’t be possible!”
“Either my measurements are wrong, or mathematics has stopped working.”
His calculations were correct.
We were already about six thousand feet deeper inside the earth than any human being had ever gone before.
The deepest places previously reached by man were the mines at Kitzbühel in Tyrol and the mines of Württemberg.
And yet, according to the depth we had reached, the temperature should have been around 81°F.
Instead, it was only about 15°C.
That strange difference between the expected heat and the actual temperature gave us something very serious to think about.