Page:Whymper - Scrambles amongst the Alps.djvu/397

the rock at any part, and retardation thickened it still more, occasionally.^[1] Are there no soft places throughout this great valley? Were there no accidents, which caused exceptional grinding on particular areas, throughout the whole of that long period during which the valley was occupied by glacier? Apparently there were not; anyhow, there are no lakes in the valley worthy of mention, nor are there, as far as can be told, any places where basins were excavated in the rock. The Professor evidently feels that the great glacier of Aosta did not behave as it should have done, and seems to be nettled by the references which have been made to its unaccountable remissness. "I have attempted," said he, "to explain why the rock-basins are present, and not why they are absent."^[2]He had, in fact, already accounted for their non-formation. He had shown that the great valleys of the Alps were approximately the same in their general features before they were filled with ice as they are at the present time. He had brought forward proof that this was the case with the Valley of Aosta, had shown that the great glacier which issued on to the plain at Ivrea had been unable to remove loose river-gravel, and had declared explicitly that the reason was that time was wanting. The entire passage is as follows:—

"When lately south of the Alps, it was proved to me by Mr. Gastaldi,^[3] that at the mouths of the great Alpine valleys opening on the plain of the Po, there were ancient alluvial fan-shaped masses of gravel quite analogous to those that by the agency of existing torrents have issued from the gorges on either side (for instance) of the valleys of the Rhone or the Dora, or of those that still issue at their mouths. These were deposited on a plain rather lower than the existing one, above Pliocene marine deposits, at a time when the true mountain valleys—at all events near their mouths—were just about as deep as they are

1. Professor Guyot has remarked striations ascending towards the mouth of the valley in places where the valley narrows. See Gastaldi's Terrains Superficiels.
2. Phil. Mag., Oct. 1864, pp. 305-6.
3. Professor Gastaldi had published the same fact more than twelve years before. "On voit au ravin du torrent de Boriana, qui descend de la tourbière de San-Giovanni, que le terrain glaciare eparpillé supporte la moraine superficielle, et se confond lui-même avec le diluvium Alpin qui repose inferieurement sur le pliocène marin."—Terrains Superficiels, 1850.