the Valleys of the Alps. 379 



• 



are unaffected by ice ; and the valleys in them, which are neither 



few nor small, have all, in the opinion of the best observers, been 

 scooped out by running water during those immense periods of 

 time the relics of which are partly represented by the subdivi- 

 sions of the Crag and of other strata still more fragmentary, all 

 of- which were deposited before the glacial epoch. During all 

 these periods, and many more, of which few traces remain, the 

 Alps were being wasted; and no geologist acquainted with the 

 evidences of the climate of the times is likely to assert that the 

 great glaciers of the Alps endured during all these changes. The 

 question, therefore, easily arises, to what extent were the Alpine 

 valleys formed during those periods that preceded the "Glacial 

 epoch "par excellence, so called from the existence of continental 

 phenomena, both in America and Europe, of which even the old 

 glaciers of the Alps form but a minor part. The evidence is 

 imperfect ; but such as it is, it gives much more than a hint 

 that the large valleys were in their main features approximately 

 as deep as now before they were filled with ice. The belief is as 

 old as the writings of Charpentier ; and others who entertain the 

 notion have only followed in his wake. 



At the mouth of the valley of Aosta, the great moraine of 

 Ivrea, which consists of loose material piled on the plain to a 

 height of about 1600 feet, proves that, where the glacier issued 

 from the valley upon the plain, the ice at the sides was at least 

 of that thickness, and probably still thicker in the middle. 

 Further, when lately south of the Alps, it was proved to me by 

 Mr. Gastaldi*, 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 now; 

 for the great glaciers that filled the larger valleys issued out 

 upon and overflowed these low-lying river gravels, and deposited 

 their moraines above them, only in part scooping them away, 

 apparently because the glaciers did not endure long enough of 

 sufficient size to complete their destruction. 



No better proof could be required that in great part the valleys 

 of the Alps were approximately as deep before the glacial epoch 

 as they are at present ; and I believe, with the Italian geologists, 

 that all that the glaciers as a whole effected was only slightly to 

 deepen these valleys and materially to modify their general out- 

 * See also memoirs by Mortillet and Omboni. 

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