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

596 D. MILNE HOME ON THE PARALLEL ROADS OF LOCHABER.
There are 3 or 4 valleys in Lochaber, to the North of Ben Nevis, each from
10 to 15 miles in length, and having a depth of from 500 to 1000 feet, the sides
of which are deeply notched by shelves called "Parallel lior/ds"; so called
l^robably, because being horizontal, they are parallel to one another, and consist
of sjiaces, so broad and regular, that a cart might be driven on them/'"
In Glen Gluoy, whose mouth opens on Loch Lochy towards the West, there
are two shelves, at a height, one of 1165, the other of 964 feet above the sea.
In Glen Roy, whose mouth also opens towards the West, there are on each
side of the Glen, for a considerable part of the valley, 3 shelves, at these respec-
tive heights above the sea (beginning with the highest)— 1149, 10G8, and 856 feet.
In Glen Spean, which in its lower part joins Glen Eoy, there is only one
well-defined shelf, 856 feet above the sea. It is a continuation of the lowest
in Glen Roy.
Dr Macculloch was too cautious to offer a decided opinion regarding the
origin of the shelves. He gave a minute and correct account of the pheno-
menon : — but he advanced no positive explanation, confessing his inability to
give any. He only suggested general views, and faither inquiry.
Sir Thomas Dick Lauder thought that the Eoads had been formed by lakes,
but he was much at a loss to account for the removal of the Barriers liy which
the lakes had been retained.
INIr Dakwin, in his paper, thought the Barrier difficulty so great, that he
deemed no other explanation possible, than that the " Jloudti " were sea-beaches.
His theory was adopted by the late Robert Chambers, Professor Nicol, Mr
Watson, and others.
Professor Agassiz and Dr Buckland accepted the theory of Lakes, and
suggested that the Lakes had l)een dammed \\]) by Glaciers ; a view taken
by a majority of subsequent inquirers, and in particular by Sir Charles Lyell,
Mr Jamieson of Ellon, and Mr Jolly of Inverness.
III. Such being the nature of the problem and the various attenqits to solve
it, let me now briefly indicate the view which I have taken. It is much the
same as that explained in my former JNIemoir : But I expect now to be able to
rest it on a wider basis of facts, and to support it on stronger grounds.
I concur with the great majority of observers, in atributing the formation of
the shelves to Lakes. My reasons are these, —
1st. In three! of the Glens, the existence of an old River Cliannel lias been
ascertained and traced, by which in each Glen, the surplus Waters of the Lakes
were discharged.
* In Glen Gluoy (as Sir Thomas Dick Lauder states) the highest shelf has a wiJtli of 100 yanls.
In Ghn Sjiean Shelf 4, ahove Inverlair House, has a width of 20' yards. (Sec fig. 17, p. 51.) In
Gl';n Gl'Uti:/-, on the side next Craig Dhu, tliis same shelf has a width of nearly 100 yards, as is
shown on the Ordnance Survey G-ineh Map.