There are two points in regard to these horizontal strata of pure ice that are worthy of consideration:—(a) Does not their existence, and especially the existence of the fine layers towards the surface, conclusively disprove the idea that the production of glacier-ice is greatly promoted by infiltration of water from the surface? (b) Can these numerous strata of pure ice (some of which are of such considerable thickness, and extending over large areas) be obliterated in the subsequent progress of the glacier? If so, how are they obliterated? Or is it not reasonable to suppose that these thick strata of solid ice must continue to exist, must continue to thicken under pressure, and must supply many of those plates of pure ice which are seen in the imperfect ice of the glacier, and which have been referred to at different times and by various persons as the 'veined structure?'
3. Below the depth of 15 feet the appearances which I have ventured to term vertical glacification were first noticed. Were they accidental? or will they be found at or about the same depth in all other places? Into what would those appearances have developed at a greater depth? What produced them? These questions may perhaps be answered one day by future investigators. I cannot answer them except by guesses or conjectures. Most unwillingly I left the excavation just at the time when it promised to yield more valuable information than it had done previously; and since then I have never been able to resume the work. I believe that the exposure of considerable sections of the interior of a glacier, at different parts of its course, would yield information of extreme interest; and that more light would be thrown in such way upon the doubts and difficulties which attend the formation of glacier-ice and the 'veined structure,' than will ever be thrown upon those vexed subjects by idle wandering upon the surface of glaciers and by peering into crevasses.
J. Denudation in the Valley of the Durance.
In the summer of 1869, whilst walking up the Valley of the Durance from Mont Dauphin to Briançon, I noticed, when about five kilomètres from the latter place, some pinnacles on the mountain-slopes to the west of the road. I scrambled up, and found the remarkable natural pillars which are represented in the annexed engraving.[1] They were formed out of an unstratified conglomerate of gritty earth, boulders, and stones. Some of them were more thickly studded with stones than a plum-pudding usually is with plums, whilst from others the stones projected like the spines from an chinoderm. The earth (or mud) was extremely hard and tenacious, and the stones, embedded in it, were extricated with considerable difficulty. The mud adhered very firmly to the stones that were got out, but it was readily washed away in a little stream near at hand. In a few minutes I extracted fragments of syenite, mica-schist, several kinds of limestone and conglomerates,
- ↑ They were 750 feet (by aneroid) above the road, and were not far from the village of Sachas. There were a dozen of about the size of those shown in the engraving, and also numerous stumps of other minor ones. There may have been more, and more considerable ones, farther behind. I was pressed for time, and could not proceed beyond the point shown in the illustration. I have thought the above imperfect account of these pinnacles worth recording, as I believe they have never been described or observed before.
