96 MR DAVID MILNE HOME: MEMOIR ON THE 
of which is 16 feet above the level of Loch Duntelchak. The channel of com- 
munication between the two lakes is very manifest. It is now filled by a bed 
of peat from 10 to 15 feet in thickness. Below the peat, there is a bed of water- 
borne gravel, and below the gravel a bed of mar! or clay. 
Loch Farraline is in Stratherrick, and about 6 miles south of Loch Ness. 
It is about 620 feet above the sea. 
It is now at least 50 feet below the level to which its waters once reached. 
Balnain House, belonging to Captain FRAsErR, on the south side of the loch, 
is on a flat which had been part of the bottom of the old lake. At Gorthleg, 
on the north side of the lake, there is asimilar flat, at the same height. 
These flats with a bounding cliff are traceable distinctly along the south 
side of Stratherrick valley, for a distance of 6 or 8 miles. The present loch is 
about one mile in length. 
But to allow of the lake standing 50 feet higher, and to extend so far 
beyond its present limits, a great blockage must have existed to the west of 
Boleskine, which blockage has entirely disappeared. This blockage probably 
consisted of the detritus, still existing in thick beds everywhere in Stratherrick, 
and which must have been removed by the Foyers and other rivers, now meander- 
ing through the valley. 
Near the upper Fall of Foyers, at Glenlia, there has been a small lake, 
about a mile in length, through which the River Foyers had flowed eastward, 
to unite with the River Inverfarrigaig. The lake waters appear to have reached 
a rent or fissure in the rocks, by the wearing away of the detrital cover, and 
through which rent the River Foyers now flows more directly into Loch Ness. 
The effect of this change in the course of the river was to drain the Glenlia 
Lake.* 
III. Probable Position of the Blockages of the Lochaber Lakes. 
1. In my last paper, I pointed out exactly where the blockage in Glen 
Collarig occurred, its position being indicated by the termination of the several 
shelves, as shown on the Ordnance Map. 
Before passing from that blockage, I may advert to the impossibility of 
accounting for the separation of the two sets of shelves, in any other way than 
by a detrital blockage, situated at a part of the glen intervening between the 
ends of the two sets of shelves. 
The two uppermost shelves, 2 and 3 of Glen Roy, terminate in Glen 
Collarig at a point shown on the map. The lake which formed them. 
* For many examples of ancient lakes, altogether or partially drained off in consequence of the wear- 
ing down of blockages of detritus, see a recent work on ‘‘The Jammoo and Kashmir Territories,” by 
Frederic Drew, F.G8., 1875. 

