Niles.] 380 [April 2, 
these prominences now exist in them, on the eroded sides of which 
the finer glacial striz are well preserved, while on the lee sides there 
are often angular rocks, which show no traces of glacial action. 
The recent and rapid recession of many glaciers has given some 
fine opportunities for studying the surface features of the rocks of 
their beds, before they become much obscured by débris and vegeta- 
tion. The ascent of the Mettelhorn from Zermatt affords an exam- 
ple. After crossing the ranges of the Blatterhorner, the course leads 
through a small elevated valley, which at no remote time was occu- 
pied by a glacier. Last summer the snow remained on the steep 
sides of the amphitheatre from which it formerly descended to form 
the neve, but the bottom was mostly bare. Here was an opportunity 
of seeing the rock surface nearly as the glacier left it. But except- 
ing the barrenness, the features were of the same general character 
as in other valleys. There were no ponds nor basin-like depressions, 
but there were roches montouncées, and ordinary forms of glaciated 
surfaces. 
From all I have observed, I am led to the belief that if we es- 
tablish our convictions concerning the agency of ancient glaciers 
_ upon what we. can observe of the work of existing ones, then we 
must conclude that glaciers were not the principal agents in the ex- 
cavation of valleys. 
I believe the geological agency of glaciers is chiefly the trans- 
portation and reduction of the rocks and stones broken from the 
mountains, mostly by frost and avalanches, and hurled down upon 
them or into their crevasses. The amount of this geological work 
performed by any glacier depends not upon its size, but upon the 
precipitous character of the sides of its valley. It often happens 
that small glaciers transport more than large ones. Standing on the 
Hornli, a spur from the Matterhorn, on one hand isthe Zmutt Gla- 
cier, whose tributaries come from the bases of the gigantic precipices 
of the Matterhorn, the Dent d’Heréns, and the Dent Blanche, and its 
surface is literally covered with moraine matter. On the other hand 
is the great Gorner Glacier, whose branches come from a region of 
extensive snow-fields, with but comparatively few bare rocks, and the 
materials which it transports would be but a mere fraction of the 
amount carried by the much smaller Zmutt Glacier. The vast fields 
of snow seem to act like a blanket for the protection of the rocks, 
rather than as a destructive agent. Some have supposed that the 
great ice sheet of the glacial period acquired an immense power from 
