159 
of Edinburgh , Session 1875-76. 
4. On the Parallel Roads of Lockaber. By David Milne 
Home, LL.D. 
( A bstract .) 
The author referred to the papers written on the subject, begin- 
ning with that by Dr Macculloch, in the year 1817 ; and he 
explained the various theories suggested. 
He intimated his adoption of the Lake theory, and expressed his 
adherence to the view he took in the memoir read by him in this 
Society in the year 1846, that the blockages of the lakes had been 
effected by detrital matter. 
In support of this view, he pointed out that all over this district 
of the Highlands there were immense beds of clay, sand, and 
gravel up to the tops of the hills, at even 2000 feet above the 
present level of the sea. 
These deposits he considered to be undeniable proofs of the 
prevalence of the sea over this part of the earth’s surface to a 
height of 3000 feet at least. 
When the sea retired, so as to expose to atmospheric action the 
higher parts of the country, there would be depressions in the sur- 
face of the land, where lakes would be formed. These lakes would 
continue at high levels, till the streams issuing from them cut 
through the detritus. In some cases, the process of erosion would 
be so gradual, that the lakes would subside without producing any 
conspicuous beach-lines on the mountain sides. In other cases, 
the removal of the blockages would be on a large scale, owing to 
the looseness of the detritus ; and if these removals were separated 
from one another by a considerable interval of time, beach-lines 
of a permanent character would be formed on the sides of the 
mountains enclosing the valleys. 
The author referred to the existence in this district of the High- 
lands, now, of several lakes at high levels, which were kept up by 
detrital blockages. He instanced, in particular, Loch Earba, in the 
Lochaber district, at a height of about 1150 feet, which was kept 
up by such means, and on whose banks there was evidence that 
the lake had once stood 30 feet higher than at present. Near 
Kingussie there was Loch Gwynae, at a height of 1015 feet above 
the sea, on whose sides there were traces of five terraces, the highest 
of which is 132 feet above the present surface of the lake. 
VOL. IX. 
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