388 SCENERY OF QUARTZITE. 



by singular hollows and pits in their course and deep cavities under 

 the cascades. A waterfall near Loch Earn Head exhibits this feature 

 remarkably. 



Examples of gneiss-like mica slate are found in Glen Tilt, Dalna- 

 cardoch, and many other points of the Blair Athole country, near 

 Tyndrum, and sparingly around the granite mountains of Arran. In 

 some specimens, as in Glen Roy, it appears composed of little else 

 than mica folded and twisted round garnet crystals ; in other cases, as 

 by Ben Nevis, the garnets form almost distinct layers. In some cases 

 (Glen Roy) the white mica and quartz form very smooth and attenu- 

 ated laminae, like those of cleavage ; in others (Trossachs, Loch Earn) 

 the quartz is in thick irregular plates, which mark one of the grada- 

 tions to quartz rock. 



Quartz Eock in Scotland. Quartzite is exhibited in a sea cliff 

 in the Whitten Head in Sutherland. Towards the sea it presents 

 caverns and stacklike pillars, but its general form is rounded. The 

 quartzite shows no trace of granular structure, and is free from veins. 

 Quartzite is seen opposite to Kyle Akin, in Skye, almost vertical, 

 highly tilted at Loch Kishhorn, and from Loch Broom to Loch 

 Urigill there is continuous quartzite underlying the limestone. Quartz 

 rocks and quartzose mica slates are seen in the North of Scotland, in 

 Moidart, along Loch Shiel and Loch Eil, and the eastern side of 

 Loch Linnhe. Above the granite of Glen Tilt quartz rocks abound 

 in Ben y gloe, and in several mountains round the granite of Braemar, 

 and may be well studied in the valley of the Bruar near Blair. They 

 reappear in Mount Alexander, and on the sides of Loch Rannoch 

 constitute the pyramidal summit of Schehallion, and on the borders 

 of the granitic desert of Rannoch Heath are traversed by granitic 

 and porphyritic veins. Quartz rock extends from Jura into Islay, 

 and is found in Shetland. 



Talcose Slates in Scotland. Talcose and chloritic slates, holding 

 an intermediate mineralogical character between clay slates and mica 

 schists, occupy for the most part an intermediate geological position. 

 They may be well studied on the banks of Loch Lomond and 

 Loch Fyne, and several points on the south slope of the Grampians, 

 where they are often rich in quartz, and remarkable for minute 

 undulations and greater contortions. Chlorite slate is also found in 

 the Long Island, and in Eetlar and Unst. The very common associa- 

 tion of garnets with mica schist and gneiss is one of the effects of 

 heat applied to those rocks since their deposition. 



Hornblende Slate in Scotland. Hornblende rocks, especially 

 hornblende slate, occur in combination with mica slate. Hornblende 

 slate is seen plentifully in Glen Tilt, and is much traversed by granite 

 veins; on both sides of the Pass of Killiecrankie ; south of Sche- 

 hallion ; north of Ben More ; in the upper part of Loch Lomond, and 

 under Ben Cruachan. 



Serpentine in Scotland. Serpentine, a rock whose geological 

 relations are still imperfectly understood, occurs to a small extent in 

 Scotland at manyplaces, accompanied generally with chlorite or steatite, 



