574 SKY. GEOLOGY. OVERLYING ROCKS. 



The greater part of the tract westward of a line drawn 

 from Loch Brittle to Loch Sriizort, consists of these rocks 

 disposed in a bedded or stratified manner, that dispo- 

 sition being easily ascertained by the deep and prolonged 

 Sections which the great range of shore presents. In the 

 interior of the country the stratified disposition often 

 ceases, and is replaced by mountainous masses, without 

 any change of composition or any apparent cause for 

 this great change of character. Even in those cases 

 where a decided difference is found between the mountain 

 mass and the stratified one, as, for example, between the 

 hypersthene rock of the Cuchullin and the ordinary trap 

 of Ru an Dunan, it is equally impossible to determine 

 the point where the one disposition ends and the other 

 begins. Similar transitions are of frequent occurrence 

 elsewhere ; and, although well known to geologists, no 

 satisfactory explanation of them has yet been proposed. 



Of the numerous species of the trap family here exist- 

 ing, basalt is among the most conspicuous, and it occurs 

 almost every where, alternating in an irregular manner 

 with all the other species or varieties. It is most fre- 

 quently amorphous, displaying at the same time so great a 

 variety both in its natural mode of breaking, in its external 

 appearance on weathering, and in its texture and colour, 

 as to form a great number of subordinate varieties much 

 more remarkable in their natural situations than when 

 broken into hand specimens. At Talisker and in other 

 situations both on the western and eastern shores, it is 

 found perfectly black, and of a very fine grain. Con- 

 sidering the great extent of this rock it is but rarely 

 columnar. The most beautiful and conspicuous collection 

 of this nature at Great Brish Meal has been already men- 

 tioned, and ranges of tolerably defined pillars are also 

 to be seen in many places of this neighbourhood occupy- 

 ing elevated situations in the cliffs. 



The next most conspicuous variety of trap in this part 

 of Sky is amygdaloidal. 1 should perhaps in strictness 



