GENERAL REMARKS ON GNEISS. 217 



feet iii height. In the northern and central parts of 

 Scotland, the prevailing features of the country are, 

 like those of Cornwall, undulating; and the gneiss is 

 generally covered with wet moory soil or with peat. 

 These undulations gradually increase in height, as- 

 suming the mountainous character and displaying broken 

 faces of rock. In further progress they produce a craggy 

 and abrupt outline ; while the mountains on the western 

 coast attain an elevation equalling the general average 

 of those throughout the country. Loch Hourn is par- 

 ticularly distinguished by the height and ruggedness 

 of the hills that surround it ; among which the district 

 of Knoydart is pre-eminent, forming indeed the wildest 

 tract in all Scotland. 



It will be immediately seen, that there are two prin- 

 cipal varieties of gneiss; the one of a granitic and the 

 other of a schistose structure. From the latter a soil 

 is formed, and general features produced, scarcely differ- 

 ing from those which occur where micaceous schist 

 is the substratum. The former is remarkable for its 

 indestructibility, and hence arises the peculiar nakedness 

 of the countries that are composed of it. Considering 

 its near resemblance to granite, a rock not often re- 

 markable for braving the effects of time and weather, 

 the causes of this power of resistance are not obvious : 

 to a certain extent they may consist in the absence 

 of fissures, denying access to frost. To this latter 

 circumstance is owing the want of springs, so conspicuous 

 throughout the Long Island; and the same considera- 

 tion explains the deficiency of recent alluvia, so general 

 in the islands of this group.* 



* A striking instance of the differences of soil resulting from this 

 distinction occurs at Strontian and in the adjoining land of Morven ; 

 the common boundary that separates the gneiss and granite being 

 rendered visible at a distance by the transition from a brown and heathy 

 to a green and grassy covering : the Litter, T need scarcely say, lies on 

 the granite. 



