240 BATHYMETRICAL SURVEY OF 



slightly oblique to the long axis of the loch, but almost parallel to 

 that of the 50-feet basins. The latter in turn have their longer axes 

 somewhat oblique to the strike of the Torridonian strata. 



Loch Ghiuragarstidh is a shallow loch lying along the strike of the 

 Torridon Sandstone, with an exposure of Lewisian gneiss near its outlet, 

 its greatest depth being 37 feet. A long ridge of sand and gravel, 

 probably a moraine, occurs near its mouth, so that this lake may lie 

 partly in drift and partly in rock. 



Loch Tollie is a true rock basin of very irregular shape, surrounded 

 by Lewisian gneiss, the deepest sounding being 86 feet. This basin 

 belongs to the shallow plateau type so common in the Archaean area 

 in the west of Sutherland. Its irregularity is due to the folding and 

 intense shearing of the component members of the Lewisian gneiss in 

 that region. Glacial striae are met with at several localities round the 

 loch, varying in direction from W. 10 N. to W. 41 N. The dominant 

 strike of the foliation of the gneiss is west-north-west and east-south- 

 east. The long axes of the bays in the loch are more in accordance 

 with the direction of the ice-flow than with the strike of the foliation. 



Loch Glair lies partly in moraine drift and partly in thrust 

 Torridonian strata. Drift occurs at the outlet and along its western 

 margin, and all the islands are composed of moraines. 



Loch Coulin is separated from Loch Clair by an alluvial fan brought 

 down by the Allt na Luib. The river Coulin has silted up the greater 

 part of the upper end of the lake, and its limits have been still further 

 restricted by detritus borne downwards by the streams on the north. 



