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. 
LocJb a' Chroisg 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 Aclumalt and Tjoch a’ Chuilinu 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. 
Ljoclb 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 
u 
