Al4 MR MILNE ON THE PARALLEL ROADS OF LOCHABER. 
about three or four miles to the north of Loch Laggan. The accumulation is enor- 
mous. Blocks are piled over each other, to sucha height as to render the general 
surface of the moor, over a wide extent, quite undistinguishable. This accumu- 
lation occurs not at the mouth of any valley. On the contrary, the hills near these 
blocks on the east side, are not much furrowed even by mountain torrents, and 
present a somewhat steep and high wall face to the west. On looking round for 
any possible explanation of the occurrence in this spot of so unusual a quantity 
of boulders, consisting almost entirely of grey granites, whilst the rocks on which 
they lie are different, I could not help noticing that the valley on the opposite or 
west side presented an opening or depression, though at the distance of 2 miles. 
This opening is the outlet of Loch Treig, and bearing about WSW. by compass. 
The appearance of the locality at once suggested the probability that the blocks 
had in some way issued through this opening, and had been transported across 
the valley to their present situation, where their farther progress was arrested 
by the lofty hills forming here the east side of Glen Spean. 
I have already stated reasons for thinking that no glacier issued from Loch 
Treig. The only alternative seems to be the agency of water. 
I proceed now to shew that the lake theory of the Lochaber shelves, and the 
principles on which I have endeavoured to account for the formation of lakes, and 
the eventual depression and drainage of them, are not inconsistent with any esta- 
blished geological truths,—but, on the contrary, receive support. from collateral 
considerations. 
1. The first circumstance which I shall notice, ¢s the occurrence of Parallel Roads 
m other valleys similar to those of Lochaber, the formation of which canbe attributed 
to no other cause than lakes. : 
[ have the less hesitation in availing myself of this argument, when I find 
Mr Darwin adverting to traces of shelves at Kilfinnin, and in the valley of the 
Spey, in support of his theory. 
But if Mr Darwin’s views are sound, traces of shelves should not be confined 
to the two localities just mentioned ; they should be visible in other parts of the 
country of equal height as the Lochaber mountains. i 
On the other hand, if it should appear that there are in many valleys, distinct 
beach lines, all horizontal, and presenting no uniformity of height above the sea, 
the argument against a sea theory will be strengthened, whilst a strong analogy 
will arise to favour the lake theory,—if these beach lines, precisely similar in all 
essential features to those of Lochaber, can, from their inland situation, and other 
circumstances, be clearly shewn to have been produced by the waters of lakes. 
I proceed therefore to mention a few localities out of many, where phenomena 
similar to those of Glen Roy are observable. 
(1.) At Inverournan (about 40 miles SW. of Lochaber) there is a lake called 
