THE FRESH-WATER LOCHS OF SCOTLAND. 289 



Ordnance datum line. The axis of the upper part of the loch coincides 

 with the strike of the crystalline schists, while that of the lower is 

 obliquely across it. It is interesting to note that the deepest basin has 

 been excavated out of the flaky muscovite biotite schists, while the 

 shallow part about the middle of the loch north of Creag Mhor cor- 

 responds with a belt of highly siliceous Moine schists folded over a core 

 of gneiss of Lewisian type. The head of the lake nearly coincides with 

 the Strath Conon fault already referred to, which crosses the lake in 

 a north-north-east direction, and has there produced considerable 

 brecciation of the strata. Only a small part has been silted up at the 

 western end by the alluvial material brought down by the Bran and 

 the Grudie. 



Loch a' ('liroixy and Loch Crann. The former lake is evidently a 

 rock basin, for, though at its outlet it flows over alluvial deposits that 

 mark the site of an old lake, the rocky barrier appears about 2 miles 

 east of Achnasheen, where the 400-feet contour-line crosses the Bran 

 river. The surface of the loch is 508 feet above Ordnance datum, and 

 the deepest sounding is 168 feet, so that the depth of the loch below the 

 rocky barrier beyond Achnasheen is 60 feet. Loch Crann has been 

 separated from Loch a' Chroisg by a cone of alluvium brought down by 

 the streams on both sides of the valley at that point. 



Loch Aduinalt and Loch a' ChuiUtui represent the remains of a lake 

 which once extended for 4 miles up the valley to Dosmuckeran, the level 

 of which has been lowered by the Bran. The materials cut through 

 during this process of denudation consisted of moraine matter, but the 

 river has now reached the solid rock. The terraces round Loch Achanalt 

 and Loch a' Chuilinn rise to a height of 20 feet above the surface of 

 these sheets of water. The deepest sounding in the former is 9 feet, and 

 in the latter 43 feet. While Loch Achanalt is being rapidly silted up 

 by alluvial detritus, Loch a' Chuilinn preserves its character of a rock 

 basin. At its outlet the water flows over an ice-moulded surface of 

 granulitic quartzose schist. The strike of the strata is nearly parallel 

 with the long axis of the loch. 



Loch Beannachan. As already indicated, this lake lies along the 

 line of the powerful fault that has been traced in a south-east direction 

 from Loch Maree and Glen Docherty. 



Loch Garve is evidently the remnant of a much larger sheet of water 

 that formerly extended from Little Garve down to the Falls of Rogie 

 a distance of about 4 miles. The former level of the lake has been 

 lowered by the erosion of the drift deposits and the cutting of the rock 

 gorge at the Falls of Rogie. The surface of the present loch is 220 feet 

 above Ordnance datum line, and the deepest sounding is 105 feet. The 

 200-feet contour-line crosses the stream at these waterfalls. Hence, 

 on the assumption that the Moine schists and epidiorite sills exposed at 



