SCOTLAND. 



for tlie corrccter details of the islands in genera), we 

 must ivii-i- to Dr. MacCulloch's general work on these, 

 comprising matters tar too extensive for our prMMtt 

 narrow s>j. 



The remaining granite of Scotland must be sought 

 in Galloway, in CntU-l, aiul in the mountains which 

 range from the Fleet along the ridge ol Cairns-muir. 



The next rock in geological order is gneiss, and this 

 forms the most extensive of the rocks in the northern 

 division of Scotland. To define it by words would be 

 a hopeless task. In Aberdeenshire, it occupies a large 

 portion of that space which is not granite; being, in 

 a superficial view, irregularly intermixed with it. On 

 the north of Scotland, if we commence near Reay in 

 Sutherland, it may be considered to predominate on 

 a line nearly due south nearly as far as Killicrankie ; 

 while, westward, it occupies tbe whole country, with 

 the exception of the granite already mentioned, of some 

 porphyry, and of some considerable tracts of quartz 

 rock and red sandstone. The future remarks on these 

 will give a better positive idea of the extent of the 

 gneiss, in the way of exception, than if we had here 

 attempted to define its most irregular boundaries. 



It is not found, as far as we yet know, to the south 

 of the Highlands, or southward of the Clyde and Tay; 

 but it forms a considerable portion of Shetland. The 

 island of Yell is nearly all composed of it, and it occu- 

 pies also a conspicuous part of the Mainland. In 

 Foula and Orkney it forms little patches accompanying 

 the granite. In the Western islands, almost the whole 

 of the long island consists of gneiss, as do Coll, Tirey, 

 and lona ; as well as Rona, and a certain portion of 

 the south-east part of Sky, and a small part of Mull, 

 connected with the granite of that island. 



The characters of this rock present endless variety in 

 Scotland, but it is nowhere used for building. A few 

 of the most fissile kinds are indeed sometimes employed 

 fpr roofing, in the windy districts, being well calculat- 

 ed by their weight, for this office. We already re- 

 marked, in the account of the Physical Geography, 

 that the general bearing of the stratification was north- 

 eastward ; and shall only further add, that though the 

 prevailing dips are southerly, they are often reversed, 

 while the angle of inclination is also very irregular. 



The next rock in order is mica slate ; and the 

 boundaries of this are somewhat more simple, at least 

 as to the larger mass, though there are many inferior 

 portions of which it would be impossible to convey an 

 accurate idea. 



This greater tract may be considered as commencing 

 at the Mull of Cantyre, extending northwards, with 

 exceptions from other intervening rocks, as far as 

 Cruachan, and then stretching across the island so as 

 to be bounded southwards by the declivities of the 

 mountains; while at the northward line, its intermix- 

 ture and alternations with other rocks are so numerous 

 and variable, that it does not admit of definition. We 

 can only remark, that it is gradually extenuated as it 

 proceeds towards the east, and that it at length disap- 

 pears. 



Independently of this great mass, mica slate occurs 

 dispersedly in various other places. It is interstrati- 

 fied with the gneiss on various occasions, and very 

 ticularly when they meet in Perthshire. On the vi^t 

 coast, itoccurs similarly among the beds of the same rock ; 

 as it does in Arran near the granite, and in Banff and 

 Aberdeenshires* both with the granite and the gneiss. 



In the islands, it exists, but is little conspicuous. 

 Jn Shetland, it is found with the gneiss in various 



places, and it occurs partially in filfciiii 



nest, and ROM, both to the eastward and 



these latter connections being similar to wbat HI 



in some of the northern islands. In tbe 



islands, it is most remarkable in Jura and 



though scanty in both, from iu 



tion with quarts rock and clay slate. In Bate, it ia 



conspicuous ; but this island is so much a part of the 



adjoining land, that we scarcely think it worth white 



to consider it separately. 



In the south of Scotland this rock is rare; but it 

 occurs occasionally on the confines of the granite, 

 though never forming a separate and noticeable tract, 

 as far as this country has yet been investigated. Mitt 

 slate is of no use ; but a soft variety, which is properly 

 the talc slate of geologists, has been used in building 

 the two magnificent houses of Inverary and Tay mouth. 



Quart/ ruck is the next in general order, and 

 forms a somewhat conspicuous substance in Scotland, rack, 

 though far inferior to mica slate in tbe extent which it 

 covers. It is at the same time so scattered that we 

 must pass suddenly from one part of 'the country to 

 another totally unconnected, in attempting to "iH'ftlT 

 its places. 



In Shetland it is found on the western shore, occu- 

 pying a space which, there, must be esteemed conside- 

 rable. In the Western islands, there is a considerable 

 tract of it in Sky ; but the chief mass lies in Jura and 

 the remainder of that chain, of which it forms a con* 

 spicuous portion. The far larger part of Lungs, 

 Scarba, and Jura, consist of quartz rock ; and the 

 Paps are entirely formed of it. In Isla also it consti. 

 tutes the much larger portion of the mountainous dis- 

 trict. 



On the mainland, it is very conspicuous and abun- 

 dant in Sutherland to the westward, and is found dis- 

 persedly along the coast of Ross-shire ; while in the 

 interior country it also forms many mountain summits, 

 occurring without names and incapable of reference. 

 We already noticed in the geography, tbe conspicuous 

 ridge of Balloch-nan-fey, and may add that it appear* 

 in Canasp and many other hills, as also at the eastern 

 extremities of Loch Torridon, Loch Broom, Loch 

 Maree, and other places in this quarter. On tbe east 

 of Sutherland it is also found in the mountains of 

 Mohr-ben and Scuir-ben. In Banff, it is equally re- 

 markable in the Knock-hill and in many other sum- 

 mits ; as, further south, it forms the summits of Ben- 

 gloe and other mountains in this neighbourhood, ex- 

 tending in a line westward, far into Breadalbane. V 

 formerly remarked that it had been applied to no use*, 

 and we cannot discover that it is known to the south 

 the Tay and Clyde. 



The next rock, clay slate, is more important from its 

 commercial value, on which we already made some re- 

 marks in treating of the commerce and manufactures 

 of the western districts. It is wrought, beside*, in 

 many places in the centre of Scotland ; as at Callander 

 and near it, near Loch Lomond, Comrie, Dunkeld. 

 BUirgowrie, and elsewhere, as well as in aome parts of 

 the south of Scotland. 



The geography of this rock is very extensive and 

 very scattered, so as to render it impossible to follow 

 the" whole of its localities without a very lengthened 

 detail, and the aid of a coloured map. And we must 

 also here premise that the geological term, clay slate, 

 does not always imply roofing slate, though this mate- 

 rial would unquestionably be found in many place* 

 where it has never yet been sought. 



