24 THE CANADIAN NATURALIST. [Feb. 



Believing, with all those who have been named, as well as with the 

 most eminent of the Swiss and French geologists, that the last 

 great up-heavals and denudations of the Alps had produced the 

 irregularities of their surface, he inferred that before the glacial 

 period began, the debris derived from the wear and tear of the 

 mountains by watery action had, to a great extent, choked up the 

 valleys and filled the rock-basins. He further believed that, in the 

 cold period which followed, great glaciers, descending with enor- 

 mous power, forced all such debris out of the original rock-basins, 

 and left them to be occupied by the present lakes. It is proper 

 here to state that M. G-astaldi was right, as well as M. Mortillet, 

 who followed him, in presuming that great deposits of old water- 

 worn alluvium or loose drift were accumulated before the formation 

 of glaciers, inasmuch as the oldest moraines are seen to repose in 

 many places on the former. It will presently be shown that this 

 fact contains within it the proof that the glaciers were not and are 

 not in themselves excavating bodies. 



Preceding M. Mortillet, however, in reasoning upon the exca- 

 vating power of former glaciers, my eminent associate, Professor 

 Ramsay, had broached a much bolder theory. In his essay en- 

 titled " The Old Glaciers of Switzerland and North Wales," pub- 

 lished in 1859, and republished with additions in 1860, he ex- 

 pressed the opinion that the excavation of deep hollows in solid 

 rocks was due to a weight of superincumbent ice pressing and 

 grinding downwards and outwards, over high, flat, and sometimes 

 broad water-sheds and table-lands, during that period of intense 

 cold which produced the old glaciers.* In 18G2 he went still 

 further ; and whilst M. Mortillet was communicating his views 

 on the continent, Ramsay, wholly unconscious of what M. Mortillet 

 was doing, read a memoir to the Geological Society of London, 

 showing that all the cavities occupied by lakes in Switzerland and 

 the North of Italy had been excavated originally by the action of 

 glacier ice. Whatever, therefore, be the fate of this ingenious 

 view, Professor Ramsay has our thanks for having excited much 

 useful enquiry, and for having compelled old geologists like myself 

 to reconsider our conclusions. 



If the view of M. Mortillet has been met with objections, still 

 more is the theory of Ramsay opposed, and particularly in foreign 



*See 'Peaks, Passes,' &c, (Alpine Journal, 1859,) and 'The Old Gla- 

 ciers of Switzerland and North Wales,' London, 1860, p. 110. 



