SCHISTS OF THE HIGHLANDS. 383 



Rocks in West of Scotland. The veins are not often filled 

 with granite of the ordinary kind, but with a compound rock, in 

 which felspar highly predominates, so as to form in several places 

 (Harris, South Uist, Eona, and Coll) a real graphic granite, which in 

 Coll contains garnets. Veins of quartz, occasionally metalliferous, 

 likewise traverse the gneiss of Coll and Tiree. Garnet, rose quartz, 

 zircon, hornblende, epidote, fluor spar, iron pyrites, and sulphide of 

 molybdena, occur in the gneiss. 



In Eona, Coll, and Tiree, mica schist alternates universally with 

 the gneiss. Gneiss occurs in many places, as round the granitic 

 mountains of Braemar and Lachin y gair, at Kincardine, in Eoss- 

 shire, and other points in the extreme North of Scotland ; but the 

 most abundant and interesting mass adjoins the granite of Strontian. 

 It forms the beautiful and picturesque region around Loch Sunart, 

 which strongly resembles the Trossachs of Loch Katrine, being 

 equally rich in wood and remarkable for intricate confusion of rugged 

 surface. The curvature to which its laminae are here subject are very 

 numerous and extraordinary ; veins of quartz, felspar, and granite are 

 extremely common, garnets abound in it at certain points, and in the 

 metalliferous veins are carbonate of strontian, harmotome, and cal- 

 careous spar. On the eastern side it is bounded by porphyritic masses, 

 but in other directions appears to be overlaid by mica schist, to which 

 its composition approximates. 



Mica Schist in the Highlands. But the principal part of the 

 Highlands is occupied by mica schist, whose layers range with more or 

 less regularity north-east and south-west, notwithstanding the inter- 

 ruption to their continuity by the unstratified rocks of the Braemar 

 mountains and the groups of Ben Cruachan and Ben Nevis. 



The south-eastern limit of this vast crystalline area is the line of 

 the foot of the Grampians from the Firth of Clyde to Stonehaven. 

 Deposits of red sandstone, lias, and a coal-bearing part of the oolites 

 border the eastern coast from the river Spey to Duncansby Head, 

 and extend through the Orkneys. Eocks of igneous origin associated 

 with schistose rocks mostly occupy the base of the volcanic regions of 

 St. Kilda, Skye, Eum, Eigg, Mull, parts of Ardnamurchan and Mor- 

 ven. Within these limits, and with the exception of irregular masses 

 of igneous rocks and of gneiss, the whole of the vast space belongs to 

 the mica slate series, with its included quartz rocks, limestones, 

 serpentines, potstones, associated hornblende slates, and talcose slates, 

 and overlying clay slates. 



Metamorphic Rocks on the Southern Slope of the Grampians. 

 Professor Nicol remarks that the clay slate extends along the 

 southern flank of the Grampians from Arran to Stonehaven. In 

 Arran it is parted from the mica slate by granite. In Bute the 

 clay slate rests on mica slate, and both dip south-east. This dip 

 extends along the Firth of Clyde, and at Gareloch the junction 

 of the mica slate and clay slate is well seen. The mica slate 

 runs up Loch Long, and is so twisted and contorted that the dip 

 is undeterminable. The rock is a lustrous slate, which towards the 



