LITERARY AND SCIENTIFIC NOTICES, 87 
they are nevertheless, in the deep-seated strata, exposed to us as close fractures 
now, and the valleys are valleys of erosion and true denudation. 
4th. They are none of them in simple synclinal basins, formed by the mere 
disturbance of the strata after the close of the Miocene epoch ; nor, 
5th. Do they lie in hollows of common watery erosion; for running water 
and the still water of deep lakes can neither of them excavate profound basin- 
shaped-hollows. So deeply did Playfair, the exponent of the Huttonian theory,. 
feel this truth, that he was fain to liken the Lake of Geneva to the petty pools 
on the New Red Marl of Cheshire, and to suppose that the hollow of the lake 
had been formed by the dissolution and escape of salts contained in the strata 
below. — 
6th. But one other agency remains—that of ice, which, from the vast size of 
the glaciers, we are certain must have exercised a powerful erosive agency. It 
required a solid body, grinding steadily and powerfully in direct and heavy con- 
tact with and across the rocks, to scoop out deep hollows, the situations of 
which might either be determined by unequal hardness of the rocks, by extra 
weight of ice in special places, or by accidental circumstances, the clue to which 
is lost, from our inability perfectly to reconstruct the original forms of the 
glaciers. 
7th. It thus follows that, valleys having existed giving a direction to the flow 
of the glaciers ere they protruded on the low country between the Alps and the 
Jura, these valleys and parts of the plain, by the weight and grinding power of 
ice in motion, were modified in form, part of that modification consisting in the 
excavation of the lake-basins under review. 
In connexion with this point, it is worthy of remark that glaciers, many of 
them very large in the modern sense of the term, on the south side of the Val- 
lais (excepting those of Mont Blanc), and the large glaciers on the south side 
of the Oberland, all drain into the Lake of Geneva; those on the north of the 
last-named snow-field, also large glaciers, are drained through the Lakes of 
Brienz and Thun. These, among the largest existing glaciers of the Alps, are 
only the shrunken tributaries of the greater glaciers that in old times filled and 
scooped out the basins of the lakes. The rest of the lakes, as already stated, 
are in equally close connexion with the old snow-drainage of glacier-regiongs 
on the grandest scale,—all of them, excepting those of Neuchatel, Bienne, 
and Morat, lying in the direct course of glaciers filling valleys that extend 
right into the heart of the mountains. 
8th. Most of the lakes are broad or deep according to the size of the glaciers 
that flowed through the valleys in which they lie, this general result being 
modified according to the nature of the rock and the form of the ground over 
which the glacier passed. Thus, the long and broad Lake of Geneva, scooped 
in the Miocene lowlands, is 984 feet deep, and over its area once spread the 
broad glacier of the Rhone. Its great breadth and its depth evince the size of 
the glacier that overflowed its hollow. The Lake of Constance, lying in the 
same strata, and equally large, is 935 feet deep, and was overspread by the 
equally magnificent glacier of the Upper Rhine. The Lakes of Maggiore and 
Como, deepest of all, lie in the narrow valleys of the harder Secondary rocks of 
