452 
MR. D. SHARPE ON THE ARRANGEMENT OF THE FOLIATION AND 
The next arch which crosses the Highlands, with a diameter of between twenty- 
five and thirty miles, runs for the most part through gneiss : its southern boundaiy 
coincides with the northern boundary of the arch just described; I only observed 
on two points the perpendicular foliation which forms its northern limit : two per- 
pendicular planes, about a mile apart bearing N. 40° E., cross the valley of the Spey, 
near the junction of the road from Loch Laggan with that which runs down Strath 
Spey, from which spot they run on through Corbuie into the line of the Monaglea 
mountains ; I observed the perpendicular again in those mountains four miles N.W. 
of Kingussie, where the regularity of its course was destroyed by the intrusion of a 
neighbouring boss of granite, and the direction of the foliation varied; but as this 
spot bears N. 40° E. from that at which the perpendicular crossed the Spey, we may 
conclude that to be the direction of the line sought for. The axis of this great arch 
runs for some distance along the central ridge of the Grampians. The great granitic 
masses of Ben Cruachan and Ben Muick Dhui, with several minor bosses of granite, 
have broken through the middle of the arch, in each instance disturbing the regu- 
larity of the foliation for some distance around ; thus in Glen Feshie, on the western 
side of the Ben Muick Dhui range, the foliation strikes for some distance nearly north, 
yet the general features of an arch are preserved, of which the crown coincides with 
the ridge separating the waters of the Feshie and Geauley. 
I have not examined the district to the west of the Ben Muick Dhui range, but 
this deficiency is partly supplied by a paper of Mr. Cunningham’s on Banffshire*. 
In the map which accompanies that memoir, the cleavage is marked as vertical Math 
a direction of N. 45° E. in the slates on the south of the town of Banff, and again 
with the same direction at Kinairdy, south of Aberchirder, while throughout nearly 
all the rest of the county the dip is represented as inclining to the S.E. at various 
angles. It appears from these data that though the direction of the foliation and 
cleavage is nearly the same on the east and west of the granite of Ben Muick Dhui, 
the whole arch on the eastern side is thrown much to the north of that on the 
western side of the granite ; for the perpendicular boundary of the arch near Banff 
is about on the line of the centre of the arch at the Grampians ; as this is the greatest 
irregularity met with in these phenomena, I regret that I had not time to work out 
the details connected with it ; but having everywhere found that the regularity of 
the foliation and cleavage is disturbed in the neighbourhood of granite, I cannot 
hesitate in ascribing this deflection to the influence of the granite which occupies so 
large a part of Aberdeenshire, and of which the northerly direction of the foliation 
in Glen Feshie is the commencement. 
I can give but a meagre account of the next line of perpendicular foliation, which 
runs nearly parallel to that last described at a distance of ten miles farther north, 
forming the northern boundary of an arch of the usual character, and of that 
diameter. The perpendicular in question runs N. 35° E. through Coryaraick, cross- 
* Journal of the Highland Society, No. 57, p. 447. 
