144 



THE GEOLOGIST. 



moutonnees, and boulders lifted above the parent-rocks indicate a northern 

 direction for the great ice-stream from Loch Treig to the 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 towards 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 Eink's and Sutherland's observations on the continental ice of Green- 

 land as affording a probable solution of these phenomena ; and, objecting 

 to the hypothesis either of floating ice and of debacles being sulBcient to 

 account for the conditions observed, he thought that land-ice, moving from 

 central plateaux downwards and outwards, has effected the extensive ero- 

 sions 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. — " On the Glacial Origin of certain Lakes in Switzerland, 

 Scotland, Sweden, and North America." By A. C. Ramsay, F.R.S., Pre- 

 sident of the Geological Society. The author first stated that in this me- 

 moir he proposed to extend his theory of the glacier-origin of the smaller 

 mountain-lakes of Wales and Switzerland (published in ' The Old Glaciers 

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

 tarns above alluded to, lie in true rocTc-hasins. 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. 

 Ail 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 Sea 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 holloivs. 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, Neu- 

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

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

 Doust be common, they need not be gaping fractures. To produce such a 

 mountain-chain, the strata are not upheaved and stretched so as to produce 

 open cracks ; on the contrary they are compressed laterally and crumpled 

 up iiilo smaller space, and the uppermost strata, that pressed heavily on 

 llu> crum])1ed rocks now visible, would prevent the formation of wide open 

 fractures below, these upper strata, as in North Wales, having, over a great 

 part of the area, been mostly or altogether removed by denudation. 

 Next, lakes of ihc rock-basin kind do not he each in an area of special sub- 

 sidence. If so, ibr instance, we should require one for the Todten See, one 

 for the Gi-iniscl, oiu^ for the ancient lake of the Kirchet, several at the foot 

 of Ihe SKulclhorn, ninny hundreds close together in Sutherlandshire, and 

 th'Misands in North AnuM-ica. 



If then the lake-basins were formed by none of the above-named causes, 



