THE FORMER EXTENSION OF GLACIERS. 
149 
Alps of smooth, and even polished rock surfaces, but 
he did not suggest any explanation. Charpentier 
pointed out that they were due to the action of 
glaciers. Running water also smooths rocks, but it 
is almost always easy to distinguish the action of 
water from that of ice. In the first place, the 
“Roches Moutonnees” are generally marked by striae, 
running in the direction of the valley, and due to 
Fig. 37. — View of the Brunberghbrner and the Juchlistock, near 
the Grimsel, showing the upper limit of glacial action. 
small stones contained in the ice, and frozen earth. 
Again, water acts most energetically in the hollows, 
ice especially on any projecting surface, so that in 
water-worn surfaces the curves are concave, while on 
“roches moutonnees” they are convex. The action 
of water is also much more irregular than that due 
to ice. 
De Saussure was also long ago struck by the fact 
