Granite of Aberdeenshire. 61 



shall not here enter : it is sufficient that the chief points have 

 been indicated in a preceding part of this paper. Limiting the 

 present remarks to deductions from the corresponding mineral 

 characters of trap and granite, which have here been pointed 

 out, the following conclusions appear justifiable. 



It is found that many important points of resemblance occur 

 between the mineral composition, the texture, and the general 

 structure and disposition, of many rocks in the trap family and 

 others in the family of granite. More particularly, it has been 

 pointed out, that, among the former, there occurs a compound 

 in no way differing from one of the most abundant varieties of 

 the latter. As the trap rocks are admitted to be of igneous 

 origin, it may be inferred that the same cause which has pro- 

 duced the granitic variety of this division, has also operated in 

 the production of the corresponding substance in the family of 

 granite. Again, it has been shown that in granite there occur 

 varieties, in no way differing from some of the prevailing rocks 

 in the trap family. Thus the analogy between the two is still 

 more closely drawn, and thus also it may be inferred, that if 

 m the latter, these rocks must be attributed to an igneous 

 origin, in granite also they have originated from the same 

 cause. And if, in this rock, it be admitted that any of the 

 varieties have an igneous origin, it is not easy to see on what 

 ground it can be denied to the remainder. 



To complete this analogy, it would have been necessary to 

 inquire, to what circumstances it is owing that the compound, 

 which is among the most rare in the family of trap, is the 

 most abundant in that of granite ; and that, on the other hand, 

 some of the most rare varieties of granite are abundant in the 

 trap family. But this inquiry is too speculative for the pur- 

 poses of the present paper, and of too discursive a nature to 

 be admissible within the limits to which it is restricted. Those 

 geologists who have turned their attention to this subject, will 

 find no difficulty in pursuing that train of reasoning which the 

 author of the present communication thus leaves in their hands. 



J.M. 

 Juney 1820. 



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