1916-17.] The Bone-Cave in the Valley of Allt nan Uamh. 333 
quartzite ridge that runs south from Breabag Tarsuinn, about the 2000-feet 
level, blocks of thrust gneiss and Moine schist have been recorded. Farther 
south, along the same ridge, north of Meall Diamhain (see map, fig. 1), 
small boulders of thrust gneiss and granulitic quartz-schist occur on out- 
crops of fucoid-beds and quartzites. The boulders of thrust gneiss have 
been derived from the slice of this material lying to the east above the 
Ben More thrust-plane. 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 that during this 
westerly movement the Moine schist erratics must have been transported 
to levels several hundred feet higher than the sources from which they 
were derived. 
Boulder clay is sparsely distributed in the mountainous district around 
InchnadamfF. It appears in the catchment basins of the Cassley and the 
Oykell, also in the upper part of the valley of the Ledbeg river. The 
drift deposits consist chiefly of moraines which have a wide distribution. 
An examination of the morainic material and of the boulders on the 
mounds points to a period of confluent glaciers when the Assynt moun- 
tains became independent centres of dispersion of the ice. In the valley 
of the Cassley river, which drains the great corries east of Ben More 
Assynt and Carn na Conbhairean, boulders of Cambrian quartzite have 
been traced for about 15 miles down to Invercassley, across the area 
occupied by the Moine schists. Again, on the Moine schist plateau south- 
east from Sgonnan Mor, moraines occur containing blocks of Cambrian 
quartzite and thrust Lewisian Gneiss which have been borne from that 
mass of high ground. 
When we pass westwards to the central region around Inchnadamff 
there is evidence to prove that local ice streamed off the eastern slopes of 
Canisp and Beinn Gharbh, which coalesced with that radiating from the 
Breabag range. Moraines of retreat are to be found near Stronechrubie 
and along the valley of the Loanan. Again, part of the confluent glacier ice 
in the neighbourhood of Inchnadamff moved northwards up the Skiag 
valley, carrying boulders of the intrusive porphyrite of Beinn Gharbh in 
its train. 
The ground around Inchnadamff is above the level of the raised beaches 
on the seaboard of the West Highlands. The surface of Loch Assynt is 
215 feet above Ordnance Datum line. We are thus deprived of evidence 
which might enable us to determine the stage when local glaciers ceased to 
exist in the mountainous region of Assynt. 
