THE FRESH-WATER LOCHS OF SCOTLAND. 239 



of the region, we prefer not to discuss its features in connection with 

 the theory of the glacial origin of lake basins. 



Loclian Fada is a simple rock basin resting partly on Torridon 

 Sandstone and partly on Lewisian gneiss. Along the greater part of 

 its course it coincides with an old pre-Torridonian valley, trending in a 

 west-north-west direction. At its eastern end it is bounded by the 

 continuation of the Glen Fhasaigh fault, which brings down the 

 Cambrian quartzite, Fucoid beds, Serpulite grit, limestone, and over- 

 lying Archaean gneiss above the Glen Logan or Kishorn thrust-plane. 

 The sudden deepening of the loch at its lower end is evidently related 

 to this fault, because harder and more durable strata on the east side 

 of this fault have been brought against the softer Torridon Sandstone 

 to the west. It is important to note that the downthrow side of this 

 fault is towards the east ; in other words, the eastern floor of Lochan 

 Fada is not faulted down to the west. It is interesting to note that the 

 deepest part of the basin, and the deepest sounding (248 feet), lie 

 between Slioch and Ben Tarsuinn, where the erosion of the ice during 

 the maximum glaciation would probably be greatest. 



Loch Garbhaig, which is situated to the north of Ben Slioch, is a 

 small lake over a mile in length, and evidently a rock basin from the 

 appearance of Lewisian gneiss at its exit, where it is drained by the 

 Amhainn na Fuirneis. The soundings prove the existence of two 

 basins separated by a ridge, the eastern one reaching a depth of 93 feet, 

 and the western 50 feet close to its outlet. This lake lies mainly along 

 the junction of the Archaean rocks and Torridon Sandstone, the older 

 rocks forming the greater part of the north shore, and the red sand- 

 stone the larger part of the south margin. A tongue of Torridon 

 breccia occupies a hollow in the Archaean rocks on the north shore, 

 where it rests on a mass of hornblende-schist. This breccia appears in 

 an island in the loch, which forms part of the ridge separating the two 

 basins. The loch may therefore be regarded as a rock basin eroded by 

 ice, mainly out of Torridon Sandstone along its line of junction with 

 the Archaean floor. 



Loch Kernsary is very irregular in shape, and has four basins below 

 the 50-feet level, the deepest sounding 93 feet being found near its 

 north-west extremity. The Archaean gneiss forms part of its north-east 

 shore, while the Torridonian rocks floor the remaining portions, save 

 near the west limit of the north shore, where a boss of Lewisian gneiss 

 projects through the Torridon Sandstone. As the Torridon sandstones 

 and conglomerates dip at angles varying from 20 to 35 to the north- 

 west, we may infer that those sediments are resting on a very uneven 

 floor of gneiss. The bed of the lake, therefore, may here correspond 

 with the pre-Torridonian surface, the softer Torridon Sandstone being 

 more easily removed than the more durable gneiss. Striae pointing in 

 a north-west direction are found round the lake, the trend of which is 



