AITNIVEESARY ADDRESS OF THE PRESIDENT. IxXXvii 



not follow, for instance, that because the Lake of Greneva does 

 not lie in a synclinal trough, it may not be in an area of depres- 

 sion, or that because the Lake of Grarda is not in an area of de- 

 pression, it may not be in a line of fracture ; and therefore I am 

 of opinion that his conclusion is not warranted, that these Alj^ine 

 lake-basins must have been caused by the excavating power of a 

 glacier in motion. 



Prof. Eamsay says that he does not believe that there are any 

 lakes now occupying yawning fractures consequent, in Switzerland, 

 on post-eocene or post-miocene disturbances ; but why does he 

 confine his argument to these Tertiary disturbances ? He has 

 himself shown in his paper in the Phil. Mag. vol. xxviii. p. 298, 

 " that the great and small outlines of mountain-chains, of valleys, 

 of river-gorges, and of plains are the combined results of an im- 

 mense number of operations, many of these going back to exceed- 

 ingly remote periods of geological antiquity, and a great proportion 

 of their details being lost even to probable conjecture." The effect 

 of those operations must have been to cause great inequalities of 

 surface even in these remote periods, partly, no doubt, by pro- 

 ducing cracks and crevices ; and if during subsequent depressions 

 these cracks and inequalities were filled up by the materials washed 

 into them, the first effect produced by their subsequent emergence 

 would be that this more recent and softer material would speedily 

 be washed out either by torrential water or atmospheric agency, 

 and thu.s valleys of greater or less depth, and greater or less 

 length would be formed, which, when the glacial period arrived, 

 would afford a ready pathway for the descent of the glaciers, by 

 which no doubt their areas would be considerably enlarged, and 

 much of the loose material still remaining be carried off. For 

 that glaciers descending from lofty mountains down valleys with 

 any considerable amount of inclination would wear away the sides 

 and bottoms of the valleys cannot be questioned. 



But this is not the point I am contesting. What appears to me 

 improbable is that a glacier, after emerging from the narrow val- 

 ley in which it has been confined, and having entered a vast plain 

 where little or no lateral pressure can be exerted, and where it has 

 reached a state of comparative if not absolute rest, should by the 

 mere force of its enormous thickness exercise such a pressure 

 upon the rocks below as to excavate a basin, in the solid rock, of 

 several hundred feet in depth. I am not aware that Prof. Eamsay 

 himself has anywhere stated that, supposing the glacier were at 

 rest, the mere vertical pressure would produce this effect upon 

 the rocks beneath. This statement has, however, been made by 

 Dr. Haast in his account of the glaciers of New Zealand, which 

 has been recently read before this Society. 



Let me now, by Avay of example, inquire into some of the cir- 

 cumstances connected with the Lake of Greneva. It is a locality 

 generally well known, and there will be no difficidty in realizing 

 its geographical position, lying as it does in the great plain of 

 Switzerland, and flanking the northern slope of the Alps as tlio 



