D. MILNE HOME ON THE PARALLEL ROADS OF LOCHABER. 607 
of the several shelves encompassing the lake, and their distance from one another. 
The surface of the lake is (approximately) 630 feet above the sea. But 
originally its waters had stood at a height of 1132 feet above the sea; and my 
position was, that the barrier which kept it in consisted of detritus which from 
time to time was eroded by the river discharging from the lake. I also stated 
that there existed still, at and near the point of discharge, “ great heaps of 
unstratified gravel,’ which form the present blockage. This statement Dr 
CHAMBERS did not question. Nevertheless, he adhered to his opinion, that the 
shelves round the lake, “may all have been produced by the sea” (page 129).* 
Another case of the same kind occurs near Kingussie. Loch Gwynac is 
about a mile in length and 300 yards wide. The present level of the loch is 
(by Ordnance Survey) 1015 feet above the sea. There are five horizontal 
terraces, traceable at the followmg heights above the lake, viz.:—26 feet, 44 
feet, 52 feet, 96 feet, and 132 feet. These terraces have been formed on the 
drift, which here as elsewhere in the Northern Highlands overspreads the whole 
country. The blockage which kept the waters of the loch up to the heights 
of these terraces has disappeared, so that there must have been enormous 
denudation and scouring out of the drift in this valley. 
The flat district north of Dunkeld, where the Dalguise and Ballingluig 
Railway Stations are situated, was formerly a lake. The old Beach line, about 
60 feet above the present level of the River Tay, is tolerably distinct. The 
blockage consisted of a mass of detritus, which was worn down and cut through 
by the river. A considerable portion of this blockage still subsists, forming a 
huge embankment transverse to the valley. 
Two years ago, when at Inverie, on the west coast of Argyleshire, Mr 
BairpD, whom I was visiting, took me to a place a few miles north on the same 
coast, called Invergussern. There I found a flat valley with a stream (the 
Gussern) meandering through it. On each side of the valley there are hills, 
along the base of which a beach line about 50 feet above the present surface was 
manifest. When I came near to the sea-shore, I found a great ridge of sand 
and gravel crossing the mouth’of the valley, and which, as it impinged on the 
hills on each side, could, so long as continuous, have effectually kept up the 
waters in the valley to form a lake. Figures 5 and 6 will assist to make this 
description intelligible. 
The River Gussern had evidently cut through the bank S S, and also a 
portion of the slate rocks beneath, and so allowed the lake to be drained. 
* A few years ago, when at Killin, at the west end of Loch Tay, I made some ascents of the hills 
adjoining, and saw traces of several lines of terrace up to a height of 890 feet above the lake, and 1240 
feet above the sea. Along the north side of the lake there is an extensive flat at a height of about 
400 feet, which seemed to have its counterpart along the south side of the lake I mention this only 
as a suggestion for farther inquiry. I believe that the late Mr M‘Laren described some terraces at the 
east end of the lake, about 40 feet above it, but I have not his papers to refer to. 
VOL. XXVII. PART IV. Ls 
