THE FRESH- WATER LOCHS OF SCOTLANH. 43 
eastern margin of wliicli nearly coincides with the course of a fault that 
crosses Loch Vennachar to the east of Lanrick. 
Th6 three lakes. Loch Doine, Loch Voil, and Loch Lubnaig, must 
have formed one continuous sheet of water in post-glacial time. Loch 
Doine is now separated from Loch Voil by two cones of alluvium, to be 
referred to presently. Loch Voil is separated from Loch Lubnaig by a 
narrow plain of alluvium 5 miles in length, the surface of Loch Lubnaig 
being 9 feet lower than that of Loch Voil. These lochs form isolated 
parts of a true rock basin. Below the outlet of Loch Lubnaig there is 
a prominent rocky barrier composed of the massive grit of Leny and 
Aberfoil, from half to three-quarters of a mile in breadth. The strike 
of this pebbly grit is north-east and south-west, and the beds are 
inclined to the north-west at high angles. 
Loch Lubnaig is traversed by several faults, to which special reference 
will be made in the sequel. The lower part of the loch coincides with 
the trend of two faults, which, in all likelihood, determined for some 
distance the course of the river in remote geological time. 
2. Glaciation. 
The glacial phenomena in the lake district of the basin of the Teith 
prove beyond doubt that, during the climax of the ice-age, the ice-shed 
lay to the north of the area now under consideration; that the ice- 
movement was more or less independent of the existing valley-system ; 
and that even the highest mountains were over-ridden by the ice. This 
great development was followed by a period of local glaciation, when 
the glaciers were confined mainly to the existing valleys, and when 
the boulder-clay or ground-moraine of the earlier period was largely 
removed. The upper limit of the valley glaciation is frequently defined 
by prominent lines of moraines strewn with boulders, which rise to a 
considerable height on the mountain-slopes. The evidence pointing to 
these conclusions may now be briefly summarized. 
On the watershed to the north of Lochs Doine and Voil, the trend 
of the ice-movement during the great glaciation, as proved by the striae, 
was S.S.E. Again, on the lofty watershed east of Loch Lubnaig and 
south of Loch Earn, between Ben Each (2660 feet) and Ben Vorlich 
(3224 feet), there is conclusive evidence that the highest mountains in 
that part of the lake district were overridden by the ice. There the 
mountains are composed of grits, and the striae are well preserved. On 
Ben Each the striae point S.E. ; on the col between that hill and Stuc a 
Chroin, S. 40° E. ; on the latter mountain about S.E., and on the slopes 
of Ben Vorlich, at a height of 2500 feet, the trend of the ice-markings is 
E. 40° S. In the tract between Loch Lubnaig and Loch Katrine similar 
evidence is obtained of a south-easterly movement at great elevations. 
For example, on Ben Vane (2685 feet), at a height of 2642 feet, the 
