GLEN ROY, IN SCOTLAND. 
65 
valleys on the mountain-slopes to the north 
and south of it, so that this valley had be¬ 
come, as it were, the great drainage-bed for 
the masses of ice thus poured into it laterally, 
and moving down the valley from east to west 
as one immense glacier. It is natural to sup¬ 
pose that, at the breaking-up of the great 
sheet of ice which, if my view of the case is 
correct, must have covered the whole country 
at this time, the ice would yield more readily 
in a valley like that of Glen Roy, lying open 
to the south and receiving the full force of the 
sun, than in those on the opposite side of Glen 
Spean, opening to the north. At all events, it 
is evident that at some time posterior to this 
universal glacial period, when the ice began to 
retreat, Glen Roy became the basin of a glacial 
lake such as we now find in the Alps of Swit¬ 
zerland, where occasionally a closed valley be¬ 
comes a trough, as it were, into which the 
Avater from the surrounding hills is drained. 
In such a lake no animals are found, such as 
exist in any other sheet of fresh water, and this 
would account for the absence of any organic 
remains on the terraces of Glen Roy. But at 
first sight it seemed that this theory was open 
