GRANITE. 53 



animals and plants found in them ; for there is scarcely any 

 kind of soil (above the primary rocks) in which abundant 



FIG, 7. 



remains of these have not been found. It will now be 

 proper to give a description of them in succession, beginning 

 at the lowest or primary, granite. 



This appears to be the result of the cooling and crystal- 

 lisation of that molten mass which many circumstances 

 (hereafter to be mentioned) point out as making up 

 the great body of the earth. Granite differs, in various 

 places, in colour and quality (the varieties are known as 

 " sienite," "porphyry," "greenstone," &c.), but still retains 

 its own distinctive characters ; it is a hard, crystalline rock, 

 consisting of " felspar," " mica," and " quartz," in separate 

 crystals, but mechanically blended ; its chemical composition 

 as a whole is silica, alumina, and potassa, with small quan- 

 tities of lime and oxide of iron. This granite is met with 

 everywhere, if the outer crust of the earth be penetrated to 

 a sufficient depth ; it however frequently exists . on the 

 surface, having no strata below it, and in some places overlies 

 other strata this, and the fact that cracks and crevices of 

 some of the lower strata are filled up with granite, which 

 could only have taken place while it was in a liquid state, as 

 in fig. 8, together with evidences of the effects of calcina- 

 tion, and other changes producible only by extreme heat, all 

 around those parts and in the strata immediately overlaying 

 the granite, point out that it was once in a state of fusion. 



Above the granite formation, in many places, especially 

 in Norway and Sweden, there is a stratum of rock called 



