CLEAVAGE OF THE ROCKS OF THE NORTH OF SCOTLAND. 
455 
If these lines were continued towards the south-west, they would converge between 
Lough Foyle and Lough Swilly in the middle of the great mica schist district of the 
North of Ireland. 
As we cannot doubt that the lines forming the opposite boundaries of each arch 
of elevation are to be regarded as of contemporary formation, the divergence above 
pointed out militates strongly against M. Elie de Beaumont’s favourite theory of 
the parallelism of contemporary mountain chains. Perhaps the explanation of the 
divergence is, that the area enclosed between each pair of lines is an ellipse of which 
we only see a portion in Scotland : this is rendered probable by the frequent occur- 
rence on the surface of gneiss of elliptical elevations on a small scale. 
The section given on Plate XXIII. fig. 1, is drawn across the Highlands in a di- 
rection transverse to the strike of the foliation ; it shows at one view, as far as its 
scale admits, the dip of the divisional surfaces of the foliation and cleavage and the 
succession of arches which have been pointed out. It commences at Kyle Rhea 
Ferry in Ross-shire, on the shore opposite to the Isle of Skye, and is traced from there 
to the east-south-east, in as straight a line as my observations admitted of, through 
Fort Augustus to the Highland border below Dunkeld, being a length of about 
ninety miles. This is as long a line as can be drawn through the district of gneiss 
and schist, and is as free from the disturbing masses of granite and porphyry as any 
section which could have been chosen. So constant is the direction of the foliation, 
that any other line across the Highlands parallel to this would exhibit all the same 
principal features, dififering only in the local disturbances. It is impossible on a 
small scale to represent the contortions of the gneiss, and the lines here given are 
only intended to represent the larger features of the phenomena, so that the section 
is hardly more than a diagram expressing general results. I have added below it a 
more theoretical diagram, fig. 2, in which the forms of the arches are completed, 
which are indicated by the lines of the true section, and the outline of the country 
added to show the relation borne by the position of the mountains and principal 
valleys to the inclination of the foliation and cleavage. 
I have but little to add respecting the district of gneiss lying to the west of the 
line from Loch Eribol to the head of Loch Maree, and which should probably be 
continued to Loch Carron ; throughout which the strike, as far as has been observed, 
is about north-west. The gneiss is only seen at intervals, between which it is covered 
up by Old Red Sandstone, so that we cannot see any continuous section, nor obtain 
a good idea of the relations of the different masses to each other. There seem to be 
a succession of arches of moderate diameter, of which we see the perpendicular walls 
standing out in relief, while the central parts between being lower are covered by 
the sandstone. It will be seen on the Map that the gneiss is vertical, both at Cape 
Wrath, at Sandwood Bay five miles south of that Cape, again vertical at Loch 
Inchard, on both sides of Storr Point, and on the north side of Loch Maree; all 
with a strike between N. 45° W. and N. 25° W. I found the same direction in the 
3 N 
MDCCCLIT. 
