176 GEOLOGY. 



of an igneous fluid, and that primitively it was altogether but 

 one incandescent mass a supposition which accords per- 

 fectly well with the calculations of astronomers, who demon- 

 strate that our planet has precisely the form which it must 

 have assumed under this hypothesis. 



As soon as the temperature of the globe decreased, through 

 the cessation of the calorific cause, a solid crust was formed 

 about the liquid mass, whence resulted a first mode of the 

 formation of rocks, operating from above to below, and which 

 must continue until the whole globe has grown cool. While 

 the planet was incandescent the atmosphere which surrounded 

 it was necessarily filled with an immense quantity of water 

 and sublimated matter, besides the gases which now compose 

 it. In proportion as the process of cooling progressed these 

 materials would be deposited upon the surface of the earth, and 

 augment the thickness of the solid stratum. When the tem- 

 perature permitted water to remain in a liquid state upon the 

 earth, a new mode of formation would be united with the 

 other, that of precipitation and crystallization. Finally, 

 ruptures of the solid crust of the globe must have taken place 

 in consequence of the pressure of fluids, or of the contrac- 

 tion of the interior parts, diminishing in volume as they grow 

 cool. 



FIRST EPOCH. 



A very dense and extensive atmosphere, produced by the 

 volatilization of certain substances, easily rendered aeriform, 

 such as water, lead, sulphur, bitumen, mercury, zinc, &c. ; 

 temperature and pressure too great to permit any living being 

 to be developed; first cooling; formation of a solid crust, 

 tending to augment every day in thickness ; formation of the 

 superior strata of the primordial soils, and of the mineral 

 crystallizations which they include ; extensive risings at the 

 surface of the soil ; Plutonic eruptions, without flames or sco- 

 rified lava; internal effusions between the strata; termina- 

 tion of the first epoch, characterized by the establishment of 

 permanent aquatic basins. 



