34 Dr. Mac Culloch on the 



other places, where, from examining the country around with 

 tlie most scrupulous accuracy, I was satisfied that no trap rocks 

 existed, I became unwilling to rest in the vague conclusion that 

 they had. been transported from some far distant situation, or 

 were the remains of masses long since vanished ; more parti- 

 cularly, as they shewed no marks of such transportation, and as 

 it was not easy to conceive that detached blocks of a small size, 

 should remain in a state of integrity, while the larger masses, 

 whence they must have been derived, had disappeared. 



Recollecting that the trap rocks so often approximated to 

 granite in their mineral characters, I was thus induced to 

 suspect that granite might also, in the same manner, vary in 

 its characters, so as to resemble the specimens which, in that 

 family, are known by the name of basalt and greenstone ; a con- 

 clusion the more probable, as many of the fine grained granites 

 in which hornblende enters as a constituent, often resemble some 

 of the greenstones of the trap family ; differing from them, 

 principally, by containing quartz ; and that basalt, in some of 

 its varieties at least, consisted of the same ingredients as 

 greenstone, in a much more minute and intimate state of 

 mixture. 



This suspicion was strengthened by the views, which have 

 long been familiar to myself and to many of the readers of this 

 paper, respecting the common igneous origin of both these 

 classes of unstratified rocks, and I was therefore induced 

 to search more minutely among the solid granite for a confirm- 

 ation of it. The incumbrance produced by the deep alluvial 

 soil of this country, for some time checked this investiga- 

 tion ; but it was at length completed, and in so many dif- 

 ferent places, as not to leave the shadow of a doubt respecting 

 the nature of the rocks in question, and of their common origin 

 and continuous connexion with the more ordinary granite of 

 the country. 



Among other places, I may now point out, for the satisfaction 

 of other geologists, some recent sections of the granite between 

 Old Rain and Meldrum, and at several other points in the same 

 neighbourhood, which cannot be more particularly designated 



