of Valleys and Lakes. 299 



which, as in the Andes, may form non-essential parts of moun- 

 tain-chains. 



I shall now make some remarks on what has been said in the 

 Address respecting the action of ice in general, and its share in 

 forming lakes that are true rock-basins in particular, taking 

 these in coDnexion with other points at issue. 



" Before entering on the consideration of the new theory of 

 the power of moving ice," Sir Roderick gives a brief review of 

 the recent progress of Alpine glacial geology, meaning by recent 

 principally those twenty-five or thirty years that have elapsed since 

 Agassiz began to insist not only on the enormous size of the old 

 glaciers of the Alps, but on what is now generally recognized as 

 the true glacial theory. " Granting to the land glacialists their full 

 demand " for the great size of the old glacier of the Rhone, it is 

 stated by Sir Roderick, backed by the authority of Sir Charles 

 Lyell, that there is nothing in that fact " which supports the opi- 

 nion that the deep cavity in which the lake [of Geneva] lies was 

 excavated by ice ;" for among other things it is " to be noticed 

 in the case of the Lake of Geneva " that it " trends from E, to 

 W., whilst the detritus and blocks sent forth by the old glacier 

 of the Rhone have all proceeded to the N. and N.N.W., or in 

 direct continuation of the line of march of the glacier which 

 issued from the narrow gorge of the Rhone. By what momen- 

 tum, then, was the glacier to be so deflected to the west that it 

 could channel or scoop out, on flat ground, the great hollow 

 now occupied by the Lake of Geneva ? And, after effecting this 

 wonderful operation, how was it to be propelled upwards from 

 this cavity on the ascent, to great heights on the slopes of the 

 Jura mountains V The same argument it is stated holds good 

 of the Rhine glacier, which I have attempted to show scooped 

 out the shallow hollow of the Lake of Constance. One would 

 suppose these questions to be so conclusive, that the mere asking 

 is enough, and any opposite views must be absurdities which no 

 man of any sound knowledge could entertain ; and yet men are 

 found who do entertain them in part or in whole, even authors of 

 great authority on geological and physical subjects, not only in 

 the three kingdoms, but on the continents of Europe and Ame- 

 rica. Now with regard to the great old glacier of the Rhine, the 

 sentence bearing on it is so worded that I am unable to make out 

 whether it is implied that in the belief of Sir Roderick Murchi- 

 son no great glacier issuing from the Upper Rhine valley ever 

 overspread the region around the Lake of Constance, or whether 

 he and M. Escher von, der Linth simply at one time could not 

 find signs of a glacier that so " plunged into the flat region on 

 the east and north u (of the Hone Sentis) " as to have scooped 

 out the cavity in which the lake lies." If the former, then Sir 



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