§ 40. THE CALEDONIAN VALLEY. 879 



extensive areas of the bed of the ocean, is gradually 

 effected.* 



40. The Caledonian Valley. — The British Islands 

 afford striking illustrations of the long-continued parallel- 

 ism in the direction of the disturbing forces. The great 

 Caledonian Valley or Glen extends through Scotland almost 

 in a straight line, from S.W. to N.E. from near Lismore 

 Island to Fort George in Moray Frith ; a distance of more 

 than a hundred miles. This magnificent glen, with its 

 system of rectilinear lochs or lakes, and friths, has been 

 produced by a wedge-shaped ridge of gneiss having been 

 upheaved in a solid mass, and forced through the stratified 

 deposits which now abut against it in highly inclined po- 

 sitions. That this vast ridge of plutonic matter was in the 

 state of a hard rock when elevated, is inferred from there 

 being no interpolations of volcanic products among the 

 contiguous Devonian strata ; and from the latter manifesting 

 no indications of the changes which would have been in- 

 duced by intense heat. Hence the sharp mountain-ridges 

 and peaks of these Alpine regions, the precipitous glens, 

 the narrow passes, and the deep lochs studded with islands, 

 presenting every variety of combination and contrast of 

 rock, and wood, and water, which constitute the sublime 

 and magnificent scenery of the Highlands. 



Now, by a reference to a geological map of England and 

 Scotland, it will be seen that the principal mountains or 

 ridges of elevation of these countries, extend in a line nearly 

 parallel with the direction of the Caledonian Valley, from 

 the Atlantic to the German Ocean. As, for example, the 

 Grampians, which have thrown up the Devonian strata on 

 their southern flank ; the nearly parallel range of the 

 great coal-field of Scotland ; the Cumbrian and Silurian 



* See Mr. Bakewell's sagacious commentary on this question 

 Introduction to Geology, p. 531. 



