484 RUM. GEOLOGY. 



this island. The sandstone undergoes in the same place 

 some changes of character which it is requisite to notice. 

 It is intersected by numerous veins of white calcareous 

 spar, varying from the dimensions of a thread to an 

 inch or more, and sometimes almost equal in quantity 

 to the including rock. In other places it becomes mi- 

 caceous, and splits into thin and straight schistose 

 laminae; while in a third it adopts a columnar mode 

 of fracture, and is separated naturally into masses re- 

 sembling fragments of basaltic pillars. 



That portion of the sandstone which is found beyond 

 Glen Debbie follows the schist in a similar manner, but 

 with a dip nearly the reverse of that just described. 

 It may be traced on the side of Ben more to perhaps 

 one fourth, or more, of its height. Along the shore its 

 course is but short, since it suddenly disappears at a 

 point between Papadil and Glen Debbie. Here the 

 strata terminate abruptly against the trap, and are much 

 disturbed; this rock appearing both above and below 

 the broken ends. 



From this description of the stratified rocks that 

 form the basis of this island, their analogy with the 

 series of rocks described in Sky is sufficiently apparent ; 

 and is such as to leave no rational doubt respecting the 

 common position and geological continuity of the strata 

 of both these islands, however interrupted by the deep 

 sea which separates them. 



On the basis of sandstone thus described, there are 

 placed three or four different kinds of rock ; two of which 

 at least are of different dates, since their relations are in 

 many places perfectly apparent, and their order in relative 

 position is easily ascertained. They may all be con- 

 sidered as appertaining to the trap family, using the 

 term in its most general sense, and they present ap- 

 pearances of considerable interest. 



On the east side of the island and immediately 

 incumbent on the sandstone, is observed a great body 



