GEOLOGY. 541 



CHAPTER II. 



PRIMARY EPOCH. 



When the globe had sufficiently cooled down, the fright- 

 ful ocean of fire which enveloped its entire surface stilled 

 its burning waves, leaving to float hither and thither a few 

 black and smoking islets, the first traces of the terrestrial 

 crust. These soon increased in thickness, and at last in- 

 vaded all the space that had formerly been in combustion. 

 Thus were formed the primary rocks ; they are all of ig- 

 neous origin, and all bear marks of fire. 



These first steps towards the solidification of the globe 

 produced the granites, which seem to be only the result of 

 the incandescent mass on the surface of the globe being 

 chilled ; hence these rocks are found everywhere. They 

 form the skeleton, the supporting arch, so to speak, of the 

 other layers which, in the lapse of ages, have accumulated 

 upon them. 



But in the beginning these chilled waves only produced 

 thin beds, which were often broken up again by the fiery 

 ocean below : in consequence of this the granites exhibit 

 great differences ; indeed, as M. Elie de Beaumont happily 

 remarks, " perhaps not a single page of these first archives 

 of our globe remains intact." The gneiss, for instance, 

 seems to be only granite which has been fused again in the 

 central fire. 



The rocks of the primary epoch being all the product of 

 a mass in the state of ignition, it is needless to say that we 



