GLEN ROY, IN SCOTLAND. 
45 
the ice above it. On the breaking up of the 
ice, therefore, such a spot will be the first to 
yield, and allow the boulders carried on the 
hack of the glacier to fall into the hollow thus 
formed, where they will rest upon the pro¬ 
jecting rock left uncovered. This is no the¬ 
oretical explanation; there are such cases in 
Switzerland, where holes in the ice are formed 
immediately above the summit of hills or 
prominences over which the glacier passes, 
and into which it drops its burdens. Of 
course, where the ice is constantly renewed 
over such a spot by the onward progress of 
the glacier, these materials may be carried oft 
again; but if we suppose such a case to occur 
at the breaking up of the glacier-period, in a 
locality from which the ice was disappearing 
forever, it is easy to account for the poising 
of these large boulders on prominent peaks or 
ledges. 
The appearances about the roches mouton- 
nees , especially the straight scratches and 
grooves on the side up which the ice ascended, 
have led to a mistaken view of the mode in 
which large boulders are transported by ice. 
It has been supposed by those who, while they 
