258 
THE GEOLOGIST. 
from Faverges, at the head of the Lake of Annecy, across Savoy. It sepa- 
rated Mont Yergi from the Mont Dorons, and the Dent d'Oche from the 
Dent du Midi ; then entered Switzerland, separating the Moleson from 
the Diablerets ; passed on through the districts of Thun and Brientz, and, 
dividing itself into two, caused the zigzagged form of the Lake of Lucerne. 
The principal branch then passed between the high Sentis and the Glar- 
nisch, and broke into confusion in the Tyrol. On the north side of this 
trench the chalk beds were often vertical, or cast into repeated folds, of 
which the escarpments were mostly turned away from the Alps ; but on 
the south side of the trench, the Jurassic, Triassic, and Carboniferous beds, 
though much distorted, showed a prevailing tendency to lean towards the 
Alps, and turn their escarpments to the central cliain. 
Both these systems of mountains are intersected by transverse valleys, 
owing their origin, in the first instance, to a series of transverse curvilinear 
fractures, which affect the forms even of every minor ridge, and produce 
its principal ravines and boldest rocks, even where no distinctly-excavated 
valleys exist. Thus, the Mont Vergi and the Aiguilles of Salouvre are 
only fragmentary remains of a range of horizontal beds, once continuous, 
but broken by this transverse system of curvilinear cleavage, and worn or 
weathered into separate summits. 
The means of this ultimate sculpture or weathering were lastly to be 
considered. 
III. Sculpture. — The final reductions of mountain form are owing either 
to disintegration, or to the action of water, in the condition of rain, rivers, 
or ice ; aided by frost and other circumstances of temperature and at- 
mosphere. 
All important existing forms are owing to disintegration or the action 
of water. That of ice had been curiously overrated. As an instrument 
of sculpture, ice is much less powerful than water ; the apparently ener- 
getic effects of it being merel}^ the exponents of disintegration. A glacier 
did not produce its moraine, but sustained and exposed the fragments 
which fell on its surface, pulverizing these by keeping them in motion, but 
producing very unimportant efiects on the rock below ; the roundings and 
striation produced by ice were superficial ; while a torrent penetrated into 
every angle and cranny, undermining and wearing continually, and carry- 
ing stones, at the lowest estimate, six hundred thousand times as fast as 
the glacier. Had the quantity of rain which has fallen on Mont Blanc in 
the form of snow (and descended in the ravines as ice) fallen as rain, and 
descended in torrents, the ravines would have been much deeper than they 
are now, and the glacier may so far be considered as exercising a protective 
influence. But its power of carriage is unlimited, and when masses of 
earth or rock are once loosened, the glacier carries them away, and exposes 
fresh surfaces. Generally, the work of water and ice is in mountain sur- 
g-ery like that of lancet and sponge — one for incision, the other for ablu- 
tion. iS^o excavation by ice was possible on a large scale, any more than 
by a stream of honey ; and its various actions, with their hmitations, were 
only to be understood by keeping always clearly in view the great law of 
its motion as a viscous substance, determined by Professor James Forbes. 
The existing forms of the Alps are, therefore, traceable chiefly to denu- 
dation as they rose from the sea, followed by more or less violent aqueous 
action, partly arrested during the glacial periods, while the produced di- 
luvium was carried away into the valley of the Ehine or into the North 
Sea. One very important result of denudation had not yet been sufficiently 
regarded ; namely, that when portions of a thick bed (as the Eudisten- 
kalk) had been entirely removed, the weight of the remaining masses, 
