336 A. C. Ramsay on the Glacial origin of certain Lakes 
and 200 feet below the level of the sea. Before the formation 
of the alluvial plain between, these two lakes were probably 
united ; and whether or not this was the case, it is evident, from 
its great depth, that the Lake of Brienz lies in a true rock-basin. 
Even if below Thun the rocks do not crop nearer than Solothurn, 
the Lake of Thun still lies in a rocky hollow more than 600 feet 
deep, both hollows having, I believe, been deepened by the great 
old glacier of the Aar, the ice of which was so thick, that above 
Brienz it overflowed into the valley of Sarnen by the Brung, 
about 1460 feet above the Aar below Meyringen, and sent 0 
a branch which scooped out the hollows of the Lakes of Lun 
gern and of Sarnen on its course towards Alpnach on the Lake 
of Lucerne. 
The Lake of Zug.—The Lake of Zug is about 9 miles long, 
from 1 to 24 wide, 1861 feet above the sea, and 1279 feet _ 
and its bottom is therefore only 82 feet above the sea. The 
whole is surrounde Miocene strata, the strike of which the 
lake cuts across, and its great depth clearly shows that it hes 
a rock-basin. 
The Lake of Lucerne-—The Lake of the Four Cantons (Lucerne) 
ramifies among the mountains and extends its arms in various 
directions. In its lower part, the branches that run N.E. to 
Kussnach and S.W. towards Gestad lie partly in the strike of the 
Miocene and older strata; but for the most part it runs across 
the average strike of the Eocene and Secondary rocks, between 
above the sea, and its recorded depth 853 feet; but the shape 0 
the banks and the round number of 800 French feet mase 
likely that it may contain deeper gulfs than have yet ea 
plumbed. If not, then its bottom is 575 feet above the sea; aT 
those acquainted with the shape of the ground by Lucerne ™ 
easily be convinced that the lake lies in an actual aaron 
The steepness of the walls of this lake more resembles the sae 
of a rent than those of any of the basins yet described, an¢ | 
re-entering angles of rock opposite curving bays have been ib 
- : : d to fit 
as evidences of fracture, one side being suppose ‘on. thete 
of running water; and, in Switzerland, ere these valleys by 
filled with ice, they existed in some shape, and were draine d _ 
rivers that deepened them and gave them a general form ari : 
ratory to the flow of the ice that largely modified their 0 
_ lines. I should no more consider the re-entering an of 
gaping fracture in these valleys than I would the ¢ at frst 
sight one were inclined to believe the space between the “ 
