﻿1861.] 



MURCHISON AND GEIKIE HIGHLANDS. 



173 



N.W. to S.E. with countless undulations, and decided inclinations at 

 all angles, both to the N.E. and S.W. 



In saying that the strike is from N.W. to S.E., it must be added 

 that this direction sometimes varies slightly to the N. and S. of 

 N.W. and S.E. ; but the normal strike is precisely that which prevails 

 also in rocks of the same mineral character on the western shores of 

 the mainland in Ross-shire and Sutherland. 



As before shown*, the strike of this old or bottom gneiss is there- 

 fore at right angles, or nearly so, to the N.E. and S.W. direction 

 of all the superjacent crystalline rocks of the mainland, including 

 the quartz-rocks and limestones, and .all the overlying formations. 

 In no part of the Lewis is this dominant strike better exhibited than 

 in the hilly deer-forest of Sir James Matheson at Morsgail. There, 

 and adjacent to the shooting-lodge, the gneiss is admirably exposed 

 in several openings, and consists of infinite alternations of highly- 

 inclined dark hornblendic and whitish quartzose laminae, which beds, 

 as exposed on the sides of a burn, are rolled over and over into 

 numerous contortions, with dips both to the S.W. and N.E. These 

 strata are every here and there diversified with protrusions of highly 

 crystalline hornblende-rock, in parts a greenstone, which rise in large 

 round masses, or are distributed in geodes and layers. The abun- 

 dance of iron in this rock occasions the decomposition of its surface 

 into holes and irregular cavities ; and numerous masses so honey- 

 combed strew the edges of Loch Morsgail. 



In the hills of Scalaval, all the gneiss, whether quartzose, horn- 

 blendic, or felspathic (more rarely micaceous), has again the direc- 

 tion from N.W. to S.E., or to points slightly deviating therefrom. 

 The same is seen in the mountainous masses along the shores of 

 Loch Langabat, where the N.E. or S.W. inclination of the beds is 

 strongly contrasted with the great transverse fissure occupied by that 

 long sheet of fresh water, which, on the contrary, is parallel to the 

 geographical axis, i. e. N.E.-S.W., and therefore nearly at right 

 angles to the strike of the ancient strata of gneiss. In short, the 

 phenomenon of the trend of the hills and valleys on the actual con- 

 figuration of the surface being transverse to the original direction of 

 the strata is as strikingly exemplified in the Lewis and Harris as it is 

 in the Harz and other masses of rock on the continent of Europe f . 



Such contrasts between the original direction of the layers of 

 deposit and the geographical outline of the islands are also strikingly 

 displayed where the low and moss-covered hills of the Lewis rise into 

 the mountains of Harris. 



Passing from Loch Seaforth into the rocky glens of Vickadell and 

 Scaladell, and under the frowning steeps of Craig Arig, the Clishan, 

 Moolan Gorran,' and Scorse Scaladell, the highly crystalline gneiss 

 (here quartzose and grey) still ranges from N.W. to S.E., and dips 

 either to the S.W. or N.E.+ 



* Quart. Journ. Geol. Soc. vol. xvi. p. 216. 



t See Quart. Journ. Geol. Soc. vol. xi. p. 449, and 'Siluria,' 1859, p. 414. 

 J These glens of Harris, radiating from lofty and steep mountains, afford 

 splendid evidences of glacial action, their mouths and flanks being studded with 



