In the floor of the little chamber there are two holes, and, stepping over these, we stood at the rear end, about eighteen meters distant from the beginning of the slope. My companion now set some birchbark on fire and dropped it into the innermost hole, and we laid down in turn, flat on the rock floor, and craned our necks through the hole. Mr. Williams thought he could see ice below us. I looked down after him and found that I was looking into a lower chamber whose sides were invisible. The floor was some three meters below vertically, and on this the birchbark was burning brightly. I think I saw some ice, but I could not be sure, as there was too much smoke to see distinctly. My companion offered to go down through the hole and get some ice; a proposition I promptly vetoed, as had anything gone wrong, I could not possibly have given him any assistance, as there was no extra rope. Mr. Williams told me that he went down several times before in July or August, and always found ice on the slanting floor. He said he did not know how far this lower chamber extended, nor the length of the ice floor. One thing which makes me hesitate to think that we saw ice was, that the temperature of the chamber where we were was not at all icy; but probably—I had forgotten my thermometer—nearly normal.
When we stood once more by the tree at the top of the slope, the mouth of another cave was visible about two meters below us. Mr. Williams said it had never looked more than a little crack before, and that the opening was much bigger than at his last visit. It was directly under the slope by which we descended and it vanished into darkness. Its direction led straight towards the lower chamber, and it almost surely leads to it. It seems thus that there are two hollows, one directly above the other; and that the lower one is a glacière, while the upper one is not. The cold air of winter would naturally sink into the lower chamber, and the spring thaws would furnish plenty of drip, so that this place seems to answer every requirement of a cave glacière.
But the most interesting fact about these caves is that, while the shallower one is a glacière, the bigger and deeper one is not. This is situated about ten meters north of the glacière and the direction of the entrance is about the same. Mr. Williams has found snow and ice in May in the entrance pit as far as the daylight goes, but none beyond. I am inclined to think that the explanation of this is the fact that the cave is a ganghöhle or tunnel cave. Mr. Williams described it as a narrow passage with chambers, and at least a hundred meters long, and fifty meters in depth below the surface. The cold air sinks in a certain distance, but as the passage is narrow and long, and too winding for any strong draughts, the cold air which enters is soon neutralized by the supply of warmer air within and by contact with the rocks. I cannot help thinking that it is by some such explanation that we must hope to solve the problem of why certain caves are glacières and others in the immediate neighborhood normal caves; and the caves near Williamstown are exceptional in presenting the problem so patently.
[PART II.]
THE CAUSES OF SUBTERRANEAN ICE.