604 D. MILNE HOME ON THE PARALLEL ROADS OF LOCHABER. 
perfectly rounded shingle” in all the valleys. ‘‘ These irregularly stratified 
beds, near the mouth of the Spean, attain a thickness of several hundred feet, 
and consist of sand and pebbles.” Mr Darwin founds specially on the existence 
of these deposits at the cols of Gluoy and Roy,—1180 feet above the sea,—in 
support of his theory that the shelves were sea-beaches (pages 43, 53, 65). 
CHAMBERS, in his “ Ancient Sea Margins” (page 123), referring first to Glen 
Roy, says ‘The bottom of the valley is jilled, to a great height, with these 
alluvial masses, insomuch as to have appeared to some as in no small degree 
diminishing the difficulty as to barriers in that glen.” Next, referring to Glen 
Spean, he says, “we find huge protuberances of detrital matter, starting out 
from the hills, and generally assuming a rude terrace-like form at 534, 627, and 
734 feet above the sea.” 
CHAMBERS refers also to what he calls “the grandest delta of the district,” 
called Unichan, occupying the lower part of Glen Spean. He describes it as 
“a mass of gravel, 11 miles long, by perhaps 2 broad, and reaching an elevation 
of 612 feet above the sea” (page 106). 
Professor Nicot of Aberdeen (who like CHAMBERS adopts the sea-beach 
theory), referring to the “col” between Glen Roy and the Spey, at a height of 1150 
feet above the sea, alludes to a line of stones left there, where the water had 
washed away the detritus. “From a lateral corry below Loch Spey,* great 
masses of detritus (he says) project into the main valley. These have been 
spread out and levelled down, as if thrown into the sea, not as if heaped 
up in a river valley” (“ Proceedings of Geol. Socy. of London,” 12th May 
1869, p. 285). 
He expresses an unhesitating opinion— 
“That before the formation of the Glen Roy lines, the whole region has been submerged in the 
sed. This is proved by the uniform coat of detritus covering the whole surface in a thicker or 
thinner sheet, according to the form of the ground. This coat is not the surface waste, but 
matter laid down by water ;—it is too wide spread and general in its distribution, and too much 
mixed in its composition, to have been formed in any mere lake.” “It is in this detrital cover 
that the dines (meaning the Parallel Roads) are cut” (page 283). 
JAMIESON, who adopts the theory of ice barriers, as suggested by AGassiz, 
takes special notice in all his papers of the extraordinary amount of detrital 
matter in the glens, and allows that there is more in ¢hese glens than in other 
Highland glens. In his paper (of 21st January 1863, “ London Geol. Society 
Journal”), he says :— 
“ Glen Roy presents an exceptional character to our other mountain glens, not only in respect 
of its Parallel Roads, but also on account of its great beds of silt and gravel, and still more the 
wonderfully fine deltas at the mouth of its lateral ravines. All these local peculiarities—the 
lines, the deltas, and the heavy banks of silt and gravel, bespeak a local cause, such as a fresh 
water lake, and not a universally present one like the sea” (“ Geol. Socy. Pro.,” 21st January 
1863, page 244). 
* Loch Spey is about 1200 feet above the sea. 


