144 
TUE GEOLOGIST. 
moutonnees, and boulders lifted above the parent-rocks indicate a northern 
direction for tlie 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, dovm the Spean. Up Glen Roy the ice had apparently passed 
north-eastwardly, over the watershed towards the Spey. In Enapdale, 
A.rg5"llshire, 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 Kink'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 sufficient 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 oS^orth America." By A. C. Eamsay, F.E.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 ^s'orth Wales ') to those greater lakes of Switzerland, which, like the 
tarns above alluded to, lie in true ?'ock-ha.sins. 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 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 ahoriginal undenuded synclinal Jiollows. Next, that they do not lie in 
areas of mere watery erosion. xS'either running water nor the still water 
of lakes can scoop large hollow basins like those of the lakes, bounded on 
all sides by rocks. Eunning 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 
must 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 into smaller space, and the uppermost strata, that pressed heavily on 
the crumpled 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 the rock-basin kind do not lie each in an area of special sub- 
sidence. If so, for instance, we should require one for the Todten See, one 
for the Grimsel, one for the ancient lake of the Kirchet, several at the foot 
of the Siedelhorn. many hundreds close together in Sutherlandshire, and 
thousands in North America. 
If then the lake-basins were formed by none of the above-named causes. 
