8 4 
SCENERY OF SWITZERLAND. 
the present day. Two hypotheses have been ad- 
vanced, which may be respectively named the hypo- 
thesis of fracture and the hypothesis of erosion. 
Those who adopt the former maintain that the forces 
by which the Alps were elevated produced fissures 
in the earth’s crust, and that the valleys of the Alps 
are the tracks of these fissures. Those who hold the 
latter hypothesis maintain that the valleys have been 
cut out by the action of ice and water, the moun- 
tains themselves being the residual forms of this 
grand sculpture. To the erosive action here in- 
dicated must be added that due to the atmosphere 
(the severance and detachment of rocks by rain and 
force), as affecting the forms of the more exposed 
and elevated peaks.”* 
This was written thirty years ago and has been 
confirmed by the subsequent researches of geologists. 
While the folding referred to in the last chapter has 
elevated the ranges and determined the position of 
many of the Swiss valleys, “fracture” has played but 
a subordinate part, and to denudation and erosion, 
as Tyndall himself always maintained, the present 
conformation of the country is mainly due. 
* Tyndall, “Conformation of the Alps,” Philosophical Mag., 
Oct. 1864. See also Scrope, “On the Origin of Valleys,” Geol. 
Mag. 1866. 
