I took with me a lantern and went around the chamber, which was now twenty-five or thirty feet in diameter, examining the new inroads which had been made upon its walls. There was a tunnel commenced opposite the one by which the chamber was entered, but it had not been opened more than a dozen feet, and it seemed to me that the men had not been working with any very great energy. I wanted to see a continuous stream of ice-blocks from that chamber to the mouth of the shaft. While grumbling thus I heard behind me a sudden noise like thunder and the crashing of walls, and, turning quickly, I saw that a portion of the roof of the chamber had fallen in. Nor had it ceased to fall. As I gazed, several great masses of ice came down from above and piled themselves upon that which had already fallen. Startled and frightened, I sprang toward the opening of the entrance tunnel; but, alas! I found that that was the point where the roof had given way, and between me and the outer world was a wall of solid ice through which it would be as impossible for me to break as if it were a barrier of rock. With the quick instinct which comes to men in danger I glanced about to see if the workmen had left their tools; but there were none. They had been taken outside. Then I stood and gazed stupidly at the mass of fallen ice, which, even as I looked upon it, was cracking and snapping, pressed down by the weight above it, and forming itself into an impervious barrier without crevice or open seam. Then I madly shouted. But of what avail were shouts down there in the depths of the earth? I soon ceased this useless expenditure of strength, and, with my lantern in my hand, began to walk around the chamber, throwing the light upon the walls and the roof. I became impressed with the fear that the whole cavity might cave in at once and bury me here in a tomb of ice. But I saw no cracks, nor any sign of further disaster. But why think of anything more? Was not this enough? For, before that ice-barrier could be cleared away, would I not freeze to death? I now continued to walk, not because I expected to find anything or do anything, but simply to keep myself warm by action. As long as I could move about I believed that there was no immediate danger of succumbing to the intense cold; for, when a young man, traveling in Switzerland, I had been in the cave of a glacier, and it was not cold enough to prevent some old women from sitting there to play the zither for the sake of a few coppers from visitors. I could not expect to be able to continue walking until I should be rescued, and if I sat down, or by chance slept from exhaustion, I must perish.