W. H. Niles—Krosion of Vaileys. 367 
as it passed the lee end of a ridge, it preserved the mould of 
the profile so perfectly that for more than twenty feet the blue 
arch presented a series of parallel furrows, like the flutings of 
a Doric column.* I also observed many other examples of the 
same kind, though none so regularly and beautifully perfect. 
_ There was there at that time another highly interesting and 
instructive exhibition of glacial action. Within a few feet of 
the down-stream end of one of these elongated roches moutonnées 
down the glacier. From the lower end of the ridge of rock I 
looked at the bowlder through a tunnel of pure, blue ice, which 
was contin s ep furrow in the under surface of the 
glacier for fully thirty feet from its beginning. As this was 
ake y the ice moving over and beyond the bowlder, it 
Property of ice. It will be understood that these stones were 
suficiently below the upper surface of the glacier to be removed 
from the effects of the ordinary changes in the temperature of 
the atmosphere. Although stones which are exposed to such 
changes may be frozen into the ice at the edges of the glaciers, 
yet I believe these were so situated as to correctly represent 
the conditions and movements of those at still greater depths. 
If this is correct, and I believe it is, it follows that such frag- 
ments of rock are not rigidly held in fixed positions in the 
under surfaces of glaciers and carried irresistibly along at the 
Same rate, but that the constantly melting ice actually flows 
over them, and that their motion is one of extreme slowness, 
€ven when compared with the motion of the glacier itself.+ 
- lL see by quotations from the “ Nouvelles Excursions et Séjours dans les Gla- 
: q m . oe 
“lets et les hautes régions des Alpes,” by Professor E. Desor, that he e de 
imilar features which he observed in connection with the Aar Glacier in 
“lon, presenting as evi f 
by him in’ 1875, near the terminations of the Glacier des Bois and the Glacier 
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