Our observations and speculations, on the motion of the ice now before us, led us to suspect that the whole of the lower body is subject to slide, and that the whole of the substratum, as frequently found within the Arctic Circle, is a slippery mud. I am satisfied that this is the case in Icy Bay, as one berg, which was well up on the shore, moved off to seaward; grounding again near what I took for Point Riou.
This leads me back to our observations on the mathematical forms observed on the 3rd, after passing Bingham Island, and I perceive that Vancouver notices not only the ice, but (at p. 209, 210, vol. iii.) attempts to account for its formation, remarking that the ice observed (before reaching Point Riou and to the southward) was not so clean, "most of them appearing to be dirty." How came they so?
If the dark, "dirty" ice had been near the beach, it could readily be accounted for, by having been agitated with the beach mud, and forced up by gales. But the reverse is the fact. The darker ice was on the high ridges, and the bright near the sea. Only the theory of a slip would allow of its moving down the inclined plane without disturbing its mathematical arrangement. Vancouver's visit occurred in the latter end of June, ours in the early part of September.
In Icy Bay, the apparently descending ice from the mountains to the base was in irregular, broken
