Dr. Mac Culloch oji the Geology of Glen Tilt. 297 



either here or in any other instance which I have met with, to 

 give a correct description of the dips of the schistose rocks which 

 occur in the highland mountains, without running into endless 

 details, since they are perpetually varying. It is perhaps fully as 

 useless as it would be laborious to the observer and tiresome to 

 the reader. These beds, at least for a short space, lie on the north- 

 ern bank of the granite mass, and stretch away in a south-east line 

 to Cairn na 'Chlavhan and Connalach more, which elevations 

 consist entirely of quartz rock. The granite continues still visible 

 to the eastward in the direction of the hills, but ceases to be red. 

 It is now grey, and shews a slight tendency to a foliated structure. 



This peculiarity of structure, imperfectly as it is marked, is an- 

 object of curiosity. I have already described a quartz rock as 

 passing by a regular transition to granite, and here the granite in 

 the vicinity of the quartz rock is found to have a foliated tendency, 

 a tendency which not improbably unites it at some point with the 

 quartz rock, although I did not discover that point of perfect 

 transition. On the same summits I also picked up a specimen of 

 genuine gneiss, but did not discover whence it had come. 



The hill of Connalach beg shews a summit of granite, but it is 

 a small space surrounded by quartz rock. The granite here passes 

 into a variety which, with the same general aspect, contains crystals 

 of hornblende. The two varieties are perfectly continuous, as con- 

 tinuous as the red and the grey, which I have just described. 



Kere then we have, as in numerous other instances, a con- 

 firmation of the geological identity of common granite, and of that 

 which is considered as a separate substance by the name of Syenite. 

 However distinct these two rocks may be considered as cabinet 

 specimens, there is no distinction in their habits and connections, nor 

 have we any reason to believe that the seras of their formation are 



Vol. III. 2 p 



