OF UNSTRATIFIEI) ROCKS AND VEINS. 157 



common scat of Granite and Trap, and the identity 

 of the circumstances in which they have originated. 

 These are deducible from similarity ; in certain cases, 

 from absolute identity of character; hut I must 

 premise, that to limit the term granite to the sole 

 compound of quartz, mica, and felspar, is merely 

 to abuse a mineralogical term for the purpose of 

 evading a geological inference. This is an expedient 

 which, however often used, is inconsistent with the 

 rules of sound logic. In a geological sense, every 

 rock must be considered a granite which, whatever 

 its composition may be, forms a portion of a common 

 mass of that rock in its most acknowledged charac- 

 ter. 



In Aberdeenshire, the leading varieties of granite 

 are of that character which agrees with the most 

 rigid mineralogical definition, and the superposition 

 of gneiss over a very extensive tract of that rock can 

 be traced with the greatest facility. But, in many 

 places, a variety of this granite occurs, which is com- 

 posed of felspar and hornblende only, passing into 

 the ordinary kind by means of the usual fourfold 

 compound of hornblende, quartz, mica, and felspar, 

 and the threefold one composed of hornblende, quartz, 

 and felspar ; to both of which the term Syenite has 

 sometimes been applied. The continuity and gra- 

 dation of all these, and their inferiority to the primary 

 strata, can be traced without the slightest difficulty. 

 In examining more minutely the duplicate compound 

 just mentioned, it is observed in many places to as- 

 sume a fine grain, and thus at length it becomes 

 undistinguishable from the greenstones of the trap 

 family. But the identity does not cease even here ; 

 since, in many places, it passes, in the same uninter- 

 rupted manner, into a basalt, and, at length, into a 



