D. MILNE HOME ON THE PARALLEL ROADS OF LOCHABER. 631 
loch. About twenty-five or thirty feet below the level of that shelf, there is 
another shelf, A B, which is situated between the termination of Shelf 4 and the 
lake, and of which we found traces on both banks of Loch Treig itself. This 
lower shelf is indicated by isolated flats consisting chiefly of a sandy mud, 
from 40 to 50 feet above the level of the lake. These flats have, no doubt, 
been originally continuous, and have been cut through, and somewhat reduced 
in level by the action of rain and of streams from the steep hills which surround 
the lake. One of these flats, consisting of a white sand horizontally stratified, 
full of rabbits, with a remarkable boulder sticking in it, is indicated by fig. 15. 
Between these two shelves, viz., between B and C, rock is visible in the 
channel of the river and close to its brink, covered by drift E. This lower 
terrace occurs on both sides of the river, as shown on fig. 16. 
















=. 









Fig 16. 
Ground plan of River Treig, near Loch Treig, showing position of two horizontal water-lines 
or shelves on both sides of the River. CD is Shelf 4, AB is a water-line from 25 to 80 feet 
lower in level. 
I observe that Mr Jamison states (“ Lond. Geol. Journ.,” vol. xix., p. 250), 
that at the mouth of Glen Treig he discovered a terrace thirty feet above No. 4 
shelf. 
There is thus a good deal of more precise observation required to clear up 
these Loch Treig terraces. But one thing is very clear. So far from there 
having been a glacier in Loch Treig when Shelf 4 was forming, Loch Treig 
must, since there are horizontal water terraces at its mouth, up to 90 feet above 
its present level, have been full of water ; and if it was full of water when Glen 
Roy lake stood at No. 4 shelf, why should it be supposed that it was not full 
of water when the same lake stood at higher levels ? 
The probability is, that the mouth of Loch Treig at that time was blocked 
with gravel, but yet not to such an extent as to prevent the waters of Shelf 4 
entering it, and that when the Glen Roy lake fell from Shelf 4, a barrier of 
some kind, rock or detritus, existed at or near the mouth of Loch Treig, which 
for some time kept its waters up to the height of shelf A B, ze., about 40 or 
50 feet above the present level of the lake. 
I referred to a remark of Mr JAmizson’s, that if any of the Parallel Roads 
had been found in Corry N‘Eoin, he would have considered it a good objection 
to the theory of Acassiz, which required a glacier to come from Corry N‘Eoin 
to provide a barrier at Unichan for Shelf 4. 
I examined the mouth of this Corry very carefully. I had not time 
VOL. XXVII. PART V. 8 LC 
