30 Dr. Mac Cullocli on the 



with which it is also intermixed in patches of various, often of 

 minute, dimensions, and of very uncertain recurrence. 



Micaceous schist also occurs ; but towards the western side 

 of the county, principally ; as it is scarcely to be found in that 

 tract where granite is the prevailing rock, and which alone is 

 the object of the present paper. 



The same remark may be made on quartz rock, which is 

 also found in considerable masses, in some of the western 

 mountains ; but it is either rare, or nearly altogether absent, in 

 those places where extensive masses of granite are visible at 

 the surface. 



Clay slate occurs in a much more conspicuous manner ; 

 forming some tracts of considerable extent and of very moderate 

 elevation ; and, in many places, being, like the gneiss, in contact 

 with the granite. It is, further, in some cases, so thin, and so 

 intermixed in patches with that rock, as obviously to form but 

 a very superficial covering over it ; the fundamental granite 

 protruding through the schist in many places, in such a manner 

 as to allow its continuity to be inferred, even in those places 

 where it does not reach the surface. 



It is unnecessary to notice particularly, the masses of ser- 

 pentine which are found in many parts of the district under 

 review ; and the more rare beds of primary limestone which lie 

 in the western and southern mountains among the other stra- 

 tified rocks. 



These then form the whole of the primary strata which occur 

 in that part of Aberdeenshire now under review. Of the 

 secondary, the lowest or old red sandstone is found in diflferent 

 places ; but, with one rather doubtful exception, it does not 

 appear that any of the superior secondary strata, whether of 

 sandstone or limestone, exist in any part of this district. 



It is, lastly, important to remark, that no instances of super- 

 incumbent trap rocks are to be discovered throughout this 

 extensive tract ; nor, after a careful research, could I find any 

 veins of these substances. That extensive body of these rocks 

 which occupies so large a portion of the central and secondary 



