482 THE FRESH-WATER LOCHS OF SCOTLAND 
distance of three miles as far as Dun Alastair, a rocky barrier appears 
at the latter point in the river and on the hill-slopes. This barrier 
culminates in Schichallion (3547 feet) and Beinn a' Chuallaich (2925 
feet) on either side of the valley. The ice moved down the valley 
from the Rannoch Moor, and it is worthy of note that the deepest 
sounding (440 feet) occurs in the centre of the largest and most 
easterly of the three small basins between the mouth of the Dall Burn 
and the foot of the loch, the locality being within two miles of Kin- 
loch Rannoch. Farther down the same depression, Loch Tummel 
furnishes another instance of a rock-basin, the rocky barrier appearing 
in the stream and on the hill-slopes at Allean House, about a mile 
below the mouth of the lake. 
Loch Ericht, along a line of shatter belt, is situated in one of the 
outlets from the Rannoch cauldron. The loch forms a simple basin, 
which is deepest where the valley is most constricted, and it shallows 
as it approaches the wider valley of the Spey. Loch Ossian — a true 
rock-basin — occurs in another gap, and likewise Loch Treig, which 
runs along a line of fault. The latter is a simple rock-basin, and, like 
many of the other lochs, is deepest where the constriction is greatest. 
A chain of small rock-basins occurs in the Leven valley, and another 
instance (Loch Triochatan) is to be found in Glencoe. Loch Tulla, 
located near the outlet of several through valleys, presents features 
characteristic of the plateau type and of the valley type of rock-basin. 
A small ice-cauldron is situated in the Monar region on the 
borders of Ross-shire and Inverness-shire, whose floor is about 700 feet 
above sea-level, while the surrounding mountains rise to above 3000 
feet. The only valley issuing from this central area is Glen Strath 
Farrar, at the head of which lies Loch Monar, a true rock-basin. In 
our notes descriptive of this basin (see Vol. II. Part I. p. 351) we have 
pointed out that the ice radiating from this cauldron during the 
period of confluent glaciers flowed eastward down Glen Strath Farrar, 
and streamed northward through some of the passes towards the 
Orrin and Glen Fhiodhaig, and westward in the direction of the 
valley of the Ling. At a later stage it escaped only by Strath Farrar. 
The rocks forming the barrier of Loch Monar are well seen in the 
gorge of Garbh-uisge, about half a mile below its present outlet, where 
they consist of massive siliceous Moine schists plicated along vertical 
axes trending north-east and south-west. Loch Calavie — a small 
rock-basin — is situated on one of the passes leading towards the Ling 
valley, and other rocky tarns are to be found near the low cols 
separating the Monar basin from the Meig and the Orrin. 
A series of valley rock-basins, comprising Lochs Arkaig, Garry, 
Loyne, Clunie, Aflric, Beinn sC Mheadhoin, Mullardoch, and 
Bunacharan, occur in the Northern Block where the rivers leave the 
