§ 5. DEVONIAN SYSTEM OF SCOTLAND. 



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5. Devonian System of Scotland. — The deposits of 

 this system occupy an important place in the geology of 

 Scotland, and have of late years attracted considerable 

 attention, from the interesting fossils they have yielded, 

 and the admirable illustrations of the most important phe- 

 nomena, given by Mr. Hugh Miller, in his delightful 

 work.* According to this charming writer, the whole of 

 the northern part of Scotland, from the Pentland Frith 

 to the mouth of the river Spey, consists of Devonian de- 

 posits resting on a central nucleus of primary rocks, viz., 

 granite, gneiss, and micaceous schists. Similar strata 

 are also found in insulated patches in various places of the 

 interior of the country. " They cap some of the higher 

 summits in Sutherlandshire ; form an oasis of sandstone 

 among the primary districts of Strathspey ; rise on the 

 northern shores of Lochness in an immense mass of con- 

 glomerate, based on a small-grained red granite, to a height 

 of three thousand feet above the sea-level ; and on the north- 

 western coast of Ross-shire, form three immense insulated 

 hills (Suil Veinn, Covl Beg, and Coul More^), of as great 



* The Old Bed- sandstone; or, Xew TValks in an Old Field. By 

 Hugh Miller. Edinburgh, 1841 : 1 vol. 12mo, with plates. 



t These insular mountains of Old Red, are cited by Dr. Macculloch 

 (Western Isles, vol. ii. p. 90), and Mr. Lyell (Elements of Geology, vol. 

 i.), as instructive examples of the vast amount of denudation which has 

 taken place in many countries. Mr. Lyell observes : " The funda- 

 mental rock of this part of Scotland is gneiss in disturbed strata, on 

 which beds of nearly horizontal red-sandstone rest unconformable*. 

 The latter are often very thin, forming mere flags, with their surface 

 distinctly ripple-marked. They end abruptly on the declivities of 

 many insulated mountains, which rise up at once to the height of 

 about two thousand feet above the gneiss of the surrounding plain or 

 table land, and to an average elevation of about three thousand feet 

 above the sea, which all their summits generally attain. It is impos- 

 sible to compare these scattered and detached portions without 

 imagining that the whole country has once been covered with a great 

 depth of sandstone, and that masses from one thousand to more than 

 VOL. II. 3 D 



