THE FRESH- WATER LOCHS OF SCOTLAND. 185 



maximum glaciation. On Quinag, at an elevation of 1750 feet, the 

 striae point W. 5 N., and on Beinn Garbh near the top, about the 

 1500-feet contour-line, the direction varies from W. 10 S. to W.S.W. 

 On the eastern slope of Canisp, between the 1250- and 1500-feet 

 contour-lines, on polished surfaces of quartzite, the striae point north 

 of west, indicating an ice-movement up the slope in the direction of 

 the Archaean plateau. On the flanks of Suilven, below the limit of the 

 Torridon Sandstone, the striae trend about west-north-west. Further 

 south, on Cul Mor, near the 1500-feet level, on the top of the escarp- 

 ment of Torridon Sandstone east of Loch Skinaskink, the direction is 

 a few degrees south of west. 



The general westerly movement of the ice across the mountainous 

 part of Assynt, the Cromalt hills, and the Coigach district is confirmed 

 by the dispersal of the boulders. Indeed, the evidence on this point is 

 somewhat remarkable. For instance, on Beinn an Fhurain, which is 

 composed of displaced members of the Cambrian formation, quartzites, 

 fucoid beds, and serpulite grit, boulders of thrust Lewisian gneiss 

 occur on the crest of the ridge, which have been borne westwards from 

 the deep corries north of Ben More Assynt. The highest elevation of 

 the thrust Lewisian gneiss in Corrie Mhadaidh is from 1750 to 2250 

 feet, and the striae on the quartzite ridge of Beinn an Fhurain west of 

 that corrie point W. 10 to 20 N. Further north, on Mullach an 

 Leathaid Riabhaich, similar boulders of thrust Lewisian gneiss rest 

 on the quartzite at a height of 2250 feet. On Breabag the evidence is 

 no less remarkable, for on the quartzite ridge that runs southwards 

 from Breabag Tarsuiim (2044 feet) about the 2000-feet level, numerous 

 blocks of thrust gneiss and Moine schist have been recorded. Further 

 south along the same ridge, in the direction of Meall Diamhain, on 

 the outcrop of fucoid beds as well as on the quartzites, blocks of thrust 

 gneiss and granulitic quartz-schist are met with. The boulders of 

 thrust gneiss have been derived from the belt of this material that has 

 teen traced continuously from Ben More Assynt south to Sgonnan Mor, 

 while the blocks of granulitic schists have been carried westwards from 

 the Moine schist area, the average height of which is lower than that 

 of the Breabag ridge. It follows, therefore, that during this westerly 

 movement the Moine schist erratics must have been borne to levels at 

 least 500 feet higher than the sources from which they were derived. 



When we pass beyond the limit of the Ben More group of mountains 

 to Cul Beag (2523 feet) a mountain of Torridon Sandstone west of the 

 Cromalt hills the evidence is equally conclusive regarding the trans- 

 port of materials in a westerly direction to higher levels. For there, 

 at a height of 2300 feet, blocks of Moine schist rest on the Torridon 

 Sandstone. Comparing the elevation of the Cromalt hills between 

 Coigach and the river Oykell with the height of these erratics on Cul 

 Beag, it is obvious that the latter must have been raised about 600 feet 



