CLEAVAGE OF THE ROCKS OF THE NORTH OF SCOTLAND. 
453 
ing the top of the pass taken by the old military road from Fort Augustus : this line 
is nearly parallel to the line of Lochs through the Great Glen, and about six miles 
south of them. I observed the cleavage of the clay slate vertical on two lines on 
the south bank of Loch Leven, one less than a mile east of the inn at Ballahulish, 
striking N. 30° E., the other, three and a half miles west of the same inn, striking N. 
40° E, : though these lines are separated from the perpendicular seen at Coryaraick 
by the granite of Ben Nevis, they obviously belong to the same boundary. 
The perpendicular line just mentioned forms the southern edge of a larger arch 
of gneiss, of which the northern boundary running through the centre of Ross-shire 
consists of several vertical lines separated by tortuous foliation, which together form 
a band several miles wide. The most southerly spot on which I crossed this band, 
was on the road from Fort William to Arasaig, on which traverse the gneiss is well 
exposed in a most instructive section : a line of vertical gneiss runs due north along 
each of the high ridges of hills between Loch Eil-head and Loch Shell, and between 
these the foliation is highly inclined and much contorted, forming with the perpen- 
diculars several of the fan-like arrangements before alluded to. Westward of Glen 
Finnen also the gneiss is vertical on several lines, gradually changing in direction as 
we go westward from N. 5° E. to N. 20° E., which last is the prevailing strike in 
that district. In taking a broad view of the phenomena, we must regard these lines 
of vertical foliation as constituting one band. 
The next traverse made was from Fort Augustus to Glenelg along Glen Morrison 
and Glen Shiel : several lines of perpendicular gneiss cross this road in the high 
region which separates the waters of the Shiel and the Clunie, viz. one at the head 
of Loch Clunie, striking N. 30° E. ; again at the Clunie inn on the top of the pass 
with the same strike, and another a mile down Glen Shiel, striking north : the pre- 
vailing direction is here N. 30° E. 
On Loch Linchart the gneiss is vertical, both at the head of the Loch and at the 
village of Garve, with a direction of N. 45° E., which would carry the latter line 
through Ben Wyvis. I did not visit the country north of this place, but in Mr. 
Cunningham’s map of Sutherland the gneiss is laid down as vertical, with a strike 
of N. 45° E. at two places on the north of the Kyle of Sutherland, beyond which I 
can only carry the line on conjecturally. 
A band drawn N. 30° E. would pass through all the above-mentioned spots in 
Ross-shire at which the foliation is vertical ; taken in connection with a line drawn 
from Ballahulish to Coryaraick, and continued eastward in the same direction, it 
incloses an arch, which at its southern extremity is not fifteen miles across, but 
which widens to twenty-five miles on the north-east : the Great Glen with its unri- 
valled chain of Lochs runs nearly parallel to the southern border of this area, half- 
way between its perpendicular boundary and the central axis of the arch : the granite 
of Loch Garry has broken through the centre, disturbing the regularity of the folia- 
tion for several miles around. 
The perpendicular band which has been traced through Ross-shire is the most 
