Soon their picks were vigorously attacking this compact matter, and huge chunks were loosened from its mass. These chunks weighed less than the water, and by an unusual effect of specific gravity, each chunk took wing, as it were, to the roof of the tunnel, which thickened above by as much as it diminished below. But this hardly mattered so long as the lower surface kept growing thinner.

After two hours of energetic work, Ned Land reentered, exhausted. He and his companions were replaced by new workmen, including Conseil and me. The Nautilus's chief officer supervised us.

The water struck me as unusually cold, but I warmed up promptly while wielding my pick. My movements were quite free, although they were executed under a pressure of thirty atmospheres.

After two hours of work, reentering to snatch some food and rest, I found a noticeable difference between the clean elastic fluid supplied me by the Rouquayrol device and the Nautilus's atmosphere, which was already charged with carbon dioxide. The air hadn't been renewed in forty-eight hours, and its life-giving qualities were considerably weakened. Meanwhile, after twelve hours had gone by, we had removed from the outlined surface area a slice of ice only one meter thick, hence about 600 cubic meters. Assuming the same work would be accomplished every twelve hours, it would still take five nights and four days to see the undertaking through to completion.

"Five nights and four days!" I told my companions. "And we have oxygen in the air tanks for only two days."

"Without taking into account," Ned answered, "that once we're out of this damned prison, we'll still be cooped up beneath the Ice Bank, without any possible contact with the open air!"

An apt remark. For who could predict the minimum time we would need to free ourselves? Before the Nautilus could return to the surface of the waves, couldn't we all die of asphyxiation? Were this ship and everyone on board doomed to perish in this tomb of ice? It was a dreadful state of affairs. But we faced it head-on, each one of us determined to do his duty to the end.

During the night, in line with my forecasts, a new one-meter slice was removed from this immense socket. But in the morning, wearing my diving suit, I was crossing through the liquid mass in a temperature of -6 degrees to -7 degrees centigrade, when I noted that little by little the side walls were closing in on each other. The liquid strata farthest from the trench, not warmed by the movements of workmen and tools, were showing a tendency to solidify. In the face of this imminent new danger, what would happen to our chances for salvation, and how could we prevent this liquid medium from solidifying, then cracking the Nautilus's hull like glass?

I didn't tell my two companions about this new danger. There was no point in dampening the energy they were putting into our arduous rescue work. But when I returned on board, I mentioned this serious complication to Captain Nemo.

"I know," he told me in that calm tone the most dreadful outlook couldn't change. "It's one more danger, but I don't know any way of warding it off. Our sole chance for salvation is to work faster than the water solidifies. We've got to get there first, that's all."

Get there first! By then I should have been used to this type of talk!

For several hours that day, I wielded my pick doggedly. The work kept me going. Besides, working meant leaving the Nautilus, which meant breathing the clean oxygen drawn from the air tanks and supplied by our equipment, which meant leaving the thin, foul air behind.

Near evening one more meter had been dug from the trench. When I returned on board, I was wellnigh asphyxiated by the carbon dioxide saturating the air. Oh, if only we had the chemical methods that would enable us to drive out this noxious gas! There was no lack of oxygen. All this water contained a considerable amount, and after it was decomposed by our powerful batteries, this life-giving elastic fluid could have been restored to us. I had thought it all out, but to no avail because the carbon dioxide produced by our breathing permeated every part of the ship. To absorb it, we would need to fill containers with potassium hydroxide and shake them continually.