Prof. B. Studer on the Origin of the Swiss Lakes. 483 



at the opening out of the Alpine valleys. This difficulty, against 

 which the genius of von Buch, De Luc, Escher, and others had 

 to struggle during the first and greater part of the present cen- 

 tury, has been one of the principal causes of the readiness with 

 which the hypothesis of the great extension of the ancient glaciers 

 has been welcomed. In this theory, the Alpine blocks have 

 been transported over the depressions between the Alps and the 

 Jura, solidly supported upon ice, instead of being suspended in 

 the air or in water at several thousand feet above the ground. 

 This general coat of ice, which covered all the valleys and all the 

 bottoms, allowed the epoch of the formation of the lakes to 

 remain undecided. They might have been anterior to the gla- 

 cial epoch, their basins during this period being filled with water 

 or ice ; and no one thought it necessary to assume that they 

 were posterior to it, so recent an origin appearing irreconcileable 

 with the evident connexion between these basins and the oro- 

 graphy of the country. 



For a long time, however, there has been known beneath the 

 erratic stratum which accompanies the blocks, abed of gravel and 

 sand horizontally stratified, and possessing all the characters of 

 a river deposit. This formation, called the old transported bed 

 {terrain de transport ancien) by Elie de Beaumont, old alluvium 

 by Necker, and diluvium by recent authors*/- is readily distin- 

 guished from the erratic stratum which is superimposed upon it. 

 The latter contains a disorderly collection of blocks of all dimen- 

 sions, and pebbles, frequently striated, in a peculiar mud which is 

 never stratified ; whilst in the lower stratum beds or long lenti- 

 cular accumulations of smooth pebbles, nearly of equal size, alter- 

 nate or interlock with lenticular or irregular masses of sand, the 

 gravel and sand being either moveable or agglutinated. On ex- 

 amining this gravel of the old alluvium, it is easily seen that its 

 pebbles are, without exception, derived from the Alps or the 

 Subalpine ridges. Like the erratic blocks, they present different 

 characters according to the valley through which they appear to 

 have been conveyed. They correspond with the rocks in posi- 

 tion in this valley and its tributary valleys. It is evident that 

 the presence of this ancient alluvium throws us back again into 

 all the difficulties from which we believed ourselves to have 



* This term should only be applied to the erratic stratum, and it would 

 be better to suppress it altogether. It was introduced, I believe, by Buck- 

 land, to designate some recent strata which appeared to him to owe their 

 origin " to a violent and transient flood," and soon afterwards it was ex- 

 tended to nearly the whole of the quaternary strata. I do not know when 

 or by whom this name was applied, in opposition to its etymology and in 

 contradiction to its original signification, to the stratum of ancient alluvium, 

 which bears all the characters of a tranquil deposit from running waters 

 acting through a long series of vears. 



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