136 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 

 metamorphic area, sections of boulder clay occur up the Tay valley as 

 far as Loch Tay, in the valleys of the Tummel 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 Rannoch and round 

 Loch Tummel. 



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 110 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 





