THE GRANITES. 465 



granite, which are often lound in veins, have probably been 

 fused a second time. The seat of the binary granites was 

 probably below that of the ternary rock, but higher than 

 the granites, Avhich contain alkaline earthy substances. 

 The general conclusion is, that the absence of mica, 

 or the presence of minerals abounding in magnesia or lime, 

 or that of metallic oxides, or a transition into syenite, por- 

 phyry, basalt, or volcanic rocks, are indications of a later 

 origin than that of ancient granite. 



We have already described the classification of the primary 

 rocks into a three-fold division, as the most natural arrange- 

 ment, and have attributed their texture and aspect to the 

 agency of fire ; the metamorphic rocks are supposed to 

 have 'been altered by its action, while the basalts and 

 granites have been reduced by it to a state of fusion ; the trap- 

 rocks having been ejected from beneath, and the granites 

 having crystallised, from a melted condition under the weight 

 and pressure of the superincumbent strata. "With reference 

 to the granites, it may be observed, that mountains of this rock 

 are usually extremely steep, and their summits present 

 those notched or serrated edges, which, in the languages of the 

 south of Europe, have occasioned the name of Sierra to be 

 bestowed on hills of this character. We have already 

 stated that granitic rocks occur as dikes and veins, 

 which * pierce the superincumbent strata, and occasion- 

 ally penetrate to the top, spreading and towering over all 

 they have displaced. We have also observed that veins of 

 granite are frequently traversed by other veins newer 

 jhan themselves (fig. 303) ; that granite is thus proved to 

 be of all ages, and to have been fluid at the close of 

 bhe secondary, and even during the tertiary epoch. We 

 have also adverted to the fact, that it has been protruded in 

 a solid as well as a fluid condition, and have instanced as 

 legative proofs of its solidity when ejected, the absence of 

 dikes or veins ramifying into the surrounding rocks, and of 

 any marks of charring or calcining; and as positive evi- 

 dence, the phenomena of rubbing and abrasion, and the 

 masses of conglomerate and breccia occurring at the line 

 of junction. We have farther alluded to the theory of 

 Dr. Hutton, who supposed that the whole of the non- 

 fossiliferous deposits, are not independent formations, but 



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