64 THE PARALLEL ROADS OF 
The general surface of the hill, consisting of 
rather soft mica, has been slightly worn down 
by atmospheric agencies, so that the dike 
stands out some three quarters of an inch 
above it. On the dike, however, the glacier- 
marks extend for its whole length in great 
perfection, while they have entirely disappeared 
from the surrounding surfaces, so as to leave 
the dike thus standing out in full relief. This 
is an instructive case, showing how little dis¬ 
integration has gone on since the drift-period. 
All the currents that have swept over it, all the 
rains that have beaten upon it, have not worn 
away one inch from the original surface of the 
hill. I have observed many other roches mow- 
tonne es in Scotland, especially about the neigh¬ 
borhood of Loch Awe, Loch Fyne, and Loch 
Etive. In fact, they may be found in almost all 
the glens of Scotland, in the lake-region of Eng¬ 
land, and in the valleys of Wales and Ireland. 
Following the glacial indications wherever 
we could find them in the country about Glen 
Roy, it became evident to me that the whole 
western range of the Grampian Hills had once 
been a great centre of glaciers, that they had 
come down toward Glen Spean through all the 
