THK KKKSH-WATER LOCHS OF SCOTLAND. 43 



eastern margin of which nearly coincides with the course of a fault that 

 crosses Loch Vennachar to the east of Lanrick. 



The 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 



