110 Proceedings of Royal Society of Edinburgh. [sess. 
prevents us from saying that Loch Muick is only a lake dammed 
up by an old frontal moraine. 
2. Penck has shown that a mass of ice coming from a semi- 
circular head would he pressed into the diameter of the same 
circle, and in order to maintain a continuous movement, an increase 
of velocity would be necessary at this place, and this increased 
velocity must affect the bed of the glacier, until a sufficient depth 
is attained. How and then the increase of depth corresponds to 
the decrease of width in the glaciated valley. On the other hand, 
a sudden increase of width in a glaciated valley is often con- 
nected with a diminution in the depth of the trough. We think 
that, in the case of Loch Muick, precisely these conditions are 
present. 
3. We pointed out that the submerged south-eastern slope was- 
far steeper than the opposite one. We may find an explanation 
of this in the fact that the glacier, being forced to change its 
course at that part, must have exerted a tremendous pressure on 
the south-eastern slope. 
We think we are justified, therefore, in saying that Loch 
Muick exhibits the characters of a rock basin and of a barrier 
basin. 
Loch Callater. 
Loch Callater is a small, narrow loch, lying in Glen Callater, 
about 5 miles to the south of Braemar, at an elevation of 1625 
feet. Its length is 0‘84 mile, and the maximum breadth 0’20 mile. 
The maximum depth recorded is 29 feet. Loch Callater is a true 
barrier basin, dammed up by a frontal moraine. The burn flowing 
out of the loch has cut its way through the moraine. At the head 
of the loch is a large alluvial tract, which evidently at one time 
formed part of the lake, when the level of the water was higher, 
and before the burn had cut its way so deeply in the barrier. 
Indeed the loch is destined to disappear in the future. By and 
by the alluvial matter will fill up the head of the loch, and simul- 
taneously the burn will cut its way deeper through the barrier,, 
until ultimately the lake will be drained and converted into an 
alluvial plain, as has been shown by Sir Archibald Geikie and 
Professor James Geikie. 
