Dr. Mac Culloch on the Geology of Glen Tilt. 277 



the left hand. But that position can onlj be called general, as in 

 every instance all particular or minute regularity disappears wherever 

 the limestone beds are found in the immediate vicinity of the gra- 

 nite. Nothing very remarkable is to be seen between this place 

 and the entrance of the Criny. Near the point of confluence beds 

 of quartz rock are distinctly seen crossing the river, and dipping 

 under the limestone to which they are parallel. 



Although various sections of the hills on each side are given by 

 the streams which fall into the Tilt, few of them are sufficiently 

 deep or explicit when singly taken to afford much information 

 about the structure of the hills. The Criny however presents a 

 section of considerable importance, which, as it illustrates the views 

 that I shall hereafter give of the whole structure of this glen, 

 may as well be described here.* 



The quartz rock which I have noticed as crossing the river, may 

 be traced through the chasm formed by this torrent, and it is found 

 reposing on limestone, which is immediately succeeded by argilla- 

 ceous schist. I am uncertain whether there is not a thin bed of schi§t 

 interposed between the quartz rock and the limestone, and I have 

 represented such a one in the engraved section; but it is not im- 

 portant, and the place is so difficult of access, while the confusion 

 produced by the waterfall is so great, that it is difficult to make 

 the investigation minutely. This alternate arrangement is found 

 immediately reposing on the granite, and the schist being the bed 

 in actual contact with the granite, is penetrated by veins precisely 

 similar to those which have already been described. The limestone 

 is here of a peculiar character, being mixed with quartz, some- 

 times in distinct concretions, sometimes in laminse irregularly 



* Vide Plate 21. fig. 1. 



