Prof. Ramsay on the Glacial Origin of certain Lakes. 413 



Spean, and then an eastern course on one hand up Loch Laggan, 

 and a western, on the other, down the Spean. Up Glen Roy the 

 ice had apparently passed north-eastwardly, over the watershed, to- 

 wards the Spey. In Knapdale, Argyllshire, similar evidence is 

 obtained of a great ice-stream passing over hill and dale, here 

 falling into the Sound of Jura. The author referred to Rink's and 

 Sutherland's observations on the continental ice of Greenland as 

 affording a probable solution of these phenomena; and, objecting 

 to the hypothesis either of floating ice and of debacles being suffi- 

 cient to account for the conditions observed, he thought that 

 land-ice, moving from central plateaux downwards and outwards, 

 has effected the extensive erosions referred to, both in Scotland and 

 other northern regions, at a time when the land was at a much 

 higher level than at present. This must have been followed by a 

 deep submergence, to account for the stratified and shell- bearing 

 drift-beds. 



March 5. — Sir P. G. Egerton, Vice-President, in the Chair. 



The following communication was read : — 



" On the Glacial Origin of certain Lakes in Switzerland, Scot- 

 land, Sweden, and North America." By A. C. Ramsay, F.R.S., 

 President of the Geological Society. 



The author first stated that in this memoir he proposed to extend 

 his theory of the glacial origin of the smaller mountain-lakes of 

 Wales and Switzerland (published in * The Old Glaciers of North 

 Wales ') to those greater lakes of Switzerland which, like the 

 tarns above alluded to, lie in true rock-basins. He then explained a 

 map, compiled from those of Charpentier, Morlot, and Mortillet, 

 showing the ancient extension of the great Alpine glaciers across 

 the Lowlands of Switzerland to the Jura, also over the area that 

 surrounds the Lake of Constance, and on the south into the plains 

 of Piedmont and Lombardy. All the great lakes of Switzerland, and 

 the lakes of Como, Lugano, and Maggiore, lie directly in the course 

 of one or other of these great glaciers; and, as shown by the 

 soundings, and the levels of the rocks at their mouths or in the 

 river-beds below, each of these lakes, like the smaller tarns of the 

 Todten See and the lake at the Grimsel, was shown to lie in a true 

 rock-basin. He then considered the question of the denudation of 

 the Alpine and Miocene areas of Switzerland, and showed that none 

 of the lakes lie in aboriginal undenuded synclinal hollows. Next that 

 they do not lie in areas of mere watery erosion. Neither running 

 water nor the still water of lakes can scoop large hollow basins like 

 those of the lakes, bounded on all sides by rocks. Running water 

 may fill them up but cannot excavate them. He next contended 

 that they do not lie in lines of gaping fracture. A glance shows 

 this with respect to such lakes as those of Geneva, Neuchatel, and 

 Constance ; and, reasoning on the nature of the contortion of the 

 strata of the Alps, he contended that, though fractures of the rocks 

 must be common, they need not be gaping fractures. To produce 

 such a mountain- chain, the strata are not upheaved and stretched so 



