42 
THE PARALLEL ROADS OF 
ledges, adapting itself readily to all the in¬ 
equalities over which it flows, and forming 
eddies against the obstacles in its course, will 
scoop out tortuous furrows upon the bottom, 
and hollow out rounded cavities against the 
walls, acting especially along pre-existing fis¬ 
sures and upon the softer parts of the rock. 
The glacier, on the contrary, moving as a 
solid mass, and carrying on its under side its 
gigantic file set in a fine paste, will in course 
of time abrade uniformly the angles against 
which it strikes, equalize the depressions be¬ 
tween the prominent masses, and round them 
off until they present those smooth bulging 
knolls known as the roches moutonnees in 
the Alps, and so characteristic everywhere of 
glacier-action. A comparison of any tide-worn 
hummock with such a glacier-worn mound 
will convince the observer that its smooth and 
evenly rounded surface was never produced by 
water. 
Besides their peculiar form, the roches mou¬ 
tonnees present all the characteristic features 
of glacier-action in their polished surfaces 
accompanied with the straight lines, grooves, 
and furrows above described. There are two 
