Dr. Mac Culloch on the Geology of Glen Tilt, 26S 



ing, nor specimens, can give an adequate idea of their disposition 

 and confusion. The drawings which accompany this paper 

 may serve to illustrate a description which can only be general, 

 since no drawing less in size than the rock itself could give an 

 accurate representation of the place.* In. contact with this great 

 mass of granite, which for a certain space offers no very particular 

 feature, are seen rocks of a schistose nature. These are succeeded 

 by blue limestone, and subsequently by schist and granite, but in 

 a state of disorder so inexplicable, that I do not attempt to describe 

 their relative positions. No appearance of parallelism is to be seen 

 in the schistose rock, but the limestone, although much bent and 

 twisted, has the aspect either of a complicated vein, or of the edges 

 of a bed in a vertical position, the portions of which have been 

 split asunder and filled with other materials. The lamellar form of 

 this limestone and its connections with the surrounding rocks, 

 leave however no doubt of its being the exposed edge of a bed, 

 and it must at the same time be remarked that besides being placed 

 in a vertical position, the line of its course is at right angles or 

 nearly so to the general bearing of the strata, of which it seems 

 once to have formed a regular constituent part. Viewing the 

 whole of this compound mass of schist and limestone as a single 

 rock, and the granite as another, it is easily seen on the most su- 

 perficial glance, from the strong contrast between the dark grey 

 of the former and the red of the latter, that the dark rock is 

 intersected and disturbed by innumerable veins of granite. 

 These traverse it in every possible direction, and are of various 

 size^, the smallest not exceeding that of a thread, and 

 reticulating the dark rock in a most intricate and amusing 



* Vide Plates 14, 15, 16, 17, 18. 



Vol. Ill 2 l 



