J. F. Campbell Collection > On the parallel roads of Lochaber

G14 D. MILNE HOME ON THE PARALLEL ROADS OF LOCHABER.
At the summit level between the two valleys, tlie hills on each side approach
one another. The shelf there is only ahoiit 20 feet above the dividing summit
ridge, and the space there, between the shelves is from 230 to 250 yards.
On the hills here, as elsewhere, there is a large amount of drift, consisting
of huge deposits of sand and rounded gravel. I saw it iip to the highest level
of the hill reached l)y me, viz., I.IIG feet above the sea.
The shelves in this valley, as elsewhere, have been formed on the detritus.
This detritus therefore had come anterior to the formation of the shelf.
I agree with Mr Darwin that this Kilfinnin shelf is of the same character as
the Lochaber shelves. The width of the shelf is not nearly so great as those in
Glen Roy. The smallness of the lake would account for this difference. It has
another feature of importance, the same as the Gleu Roy shelves. Its .slope
''///""' 1 I 'III I ill I 'I „i I, I, 1 1 /,i)i'i(f lj;lii )i I 1 \\ \ I \^ \\\\^ V
Fig. 12.
Plan (not to any scale) of part of Locli Ness, to show where deposits of detritus now exist.
down from the hillside towards the centre of the valley is exceedingly slight —
indeed, hardly pcrceptiljlc.
On this account I am inclined to think that this shelf was made, not by the
sea, as Mr Darwin thought, but by a lake. A sea beach, owing to the action
of the tides and waves, never can be so horizontal as the beach of a small lake.
But if a lake, where was the blockage both for Glen Laggan and for Glen
Buck ■?
The most probable explanation seems to bo, that t/ie (rrcat Gh'ti had here
iiho, been filled f/// detritus up to a ]iei(jht e.reeeiliiKj ViOi) feet. Indeed, I cannot
doubt that the whole of that great valley, from Fort William to Inverness, nuist
have been, at the epoch now referred to, filled witli detritus ; and that the
extensive gravel hills at the East end near Inverness (Tor Vane and Tom-
nahurich) are remnants of this detritus.
That this was really the case seems plain, from the numerous I'emnants of
detritus which occur along both sides of the Caledonian Canal.
Fig. 12 represents a small portion of Loch Ness near Foyers. TIic jiarts
marked 1, 2, 3, 4, 5,* represent accumulations of drift, which in some cases
* No. 1 is Iluiski!. No. 2, Luin. No. 3, Uniuhavt. No. 4, Koyei's. No. T), Invcrfarrigaig.