GEOLOGY. 177 



PRIMITIVE EARTHS. 



The primitive earths are composed principally of granitic 

 rocks, of schist, mica or talc, and of amphibolous rocks. 



Three substances predominate in the rocks of the primary 

 formation : these are mica, a very brilliant mineral, of variable 

 colour, and metallic appearance, composed of very fine leaves, 

 easily detached ; feldzpar, a mineral often found in red crys- 

 tals, square and elongated ; quartz, a rock-crystal, and very 

 hard body, striking fire with steel. When these three mine- 

 rals are equally disseminated, in grains more or less thick, the 

 rock which results is called granite. As one of the three pre- 

 dominates, or is mixed with some new mineral, the rock takes 

 a different name. Thus primordial rocks, disposed in lami- 

 nae, where mica or talc predominates, sometimes even exclud- 

 ing feldzspar, are termed schistous, micaceous, or talcous. 

 Amphibolous rocks are the same as the preceding, with the 

 exception that the mica is here replaced by a very brilliant, 

 greenish mineral, with a great tendency to assume elongated 

 forms ; it is called amphibola. 



USEFUL MATTERS OF THE PRIMARY FORMATION. 



Massive granite, fit to be carved into columns, and other 

 stone work of great dimensions. 



Kaolin and petunze, of which porcelain is made. 



Fine rock quartz, proper for the fabrication of crystal. 



The fine statuary marble, cipolin, verd-antique. 



White gypsous alabaster, of ancient formation. 



Topaz, amethyst, &c. 



Muscovy glass. 



Labrador and Amazon stone. 



SECOND EPOCH. 



Appearance of organized beings 1st. Vegetables; 2d. 



Aquatic marine animals ; 3d. Amphibious reptiles ; tremors 



of the earth and frequent swellings, producing only extensive 



undulations upon the surface, and no high mountains, as yet; 



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