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BATHYMETRICAL SURVEY OF 
watershed into Glen Almond. Again, all along Strath Fillan, Loch 
Tay, and Strath Tay, boulders of the Perthshire quartzite, black 
schist, limestone, and calc-sericite schist have been carried several miles 
to the south of the various belts from which they were derived. Of 
course, in many of these instances, the boulders may have been dis- 
tributed during the later glaciation. On the slopes of Ben More (3843 
feet), which is composed of grits of the Ben Ledi group, blocks of calc- 
sericite schist occur that have been carried from the hills to the 
north-north- west in the direction of the Mamlorn forest. Confirmatory 
evidence is furnished by the dispersal of the stones in the boulder clay — 
a deposit formed during the great extension of the ice. Within the 
met amorphic area, sections of boulder clay occur up the Tay valley as 
far as Loch Tay, in the valleys of the Tumniel and the Garry as far as 
Struan, and in Strath Bran from Amulree to Dunkeld. Outlying 
patches are found also at the east end of Loch Hannoch and round 
Loch Tunimel. 
After the stage of the great ice-sheet, there followed a period of 
confluent glaciers when the ice was still thick enough to stream over 
passes connecting adjoining valleys, as, for instance, over some of the 
cols between Glen Lyon and Glen Lochay, between Glen Lyon and Loch 
Tay, and between Glen Lochay and Glen Dochart, between the upper 
course of the Tay and Strath Bran, and between Loch Tay and Glen 
Almond. Again, the glacier which moved eastward from the high 
mountains in Black Mount forest and at the head of Glen Coe and Glen 
Etive was deflected southwards, part of it flowing into Glen Orchy, and 
part into Strath Fillan. The numerous groups of moraines, frequently 
showing a terraced arrangement along the hill slopes, indicate the great 
development of the later glaciation. Fine examples of the local 
dispersion of moraines are to be found in the neighbourhood of the 
Black Mount forest and the mountains round the head of Glen Etive 
and Glen Coe. The debris of Old Red Sandstone volcanic rocks have 
been traced in the moraines eastwards from the Black Mount forest to 
the drift-covered plateau at Loch Ba. 
Within the Tay basin by far the larger number of the lochs lie in 
the midst of drift deposits, most of which are of no great size, and are 
comparatively shallow. In the southern part of the Moor of Rannoch, 
along the river Ba and its tributaries, in Allt Lochain Ghaineamhaich, 
and on the drift plateau, about twenty-five lochs occur in the midst of 
morainic drifts. Numerous examples of this type occur in other parts 
of the basin. 
Again, several lochs, some of which are of considerable size, lie 
along lines of displacement, or fault-lines, for which reason they need 
not now be discussed. For example. Loch Ericht and Loch Laidon are 
situated on one line of disruption which has been traced over a con- 
siderable distance in the eastern Highlands. Loch Garry, at the head 
