MODERN GEOLOGY 



of the repressive force, consisting of the weight of its 

 fluid envelope, having reached an equilibrium with the 

 expansive force, consisting of the caloric of the heated 

 nucleus) , the rapid superficial evaporation of the ocean 

 continued ; and, by gradually reducing its temperature, 

 occasioned the precipitation of a proportionate quan- 

 tity of the minerals it held in solution, particularly its 

 silex. These substances falling to the bottom, ac- 

 companied by a large proportion of the matters held 

 in solution, particularly the mica, in consequence of 

 the greater comparative tranquillity of the ocean, ag- 

 glomerated these into more or less compact beds of 

 rock (the mica-schist formation), producing the first 

 crust or solid envelope of the globe. Upon this, other 

 stratified rocks, composed sometimes of a mixture, 

 sometimes of an alternation of precipitations, sedi- 

 ments, and occasionally of conglomerates, were by 

 degrees deposited, giving rise to the transition forma- 

 tions. 



41 Beneath this crust a new process now commenced. 

 The outer zones of crystalline matter having been sud- 

 denly refrigerated by the rapid vaporization and par- 

 tial escape of the water they contained, abstracted 

 caloric from the intensely heated nucleus of the globe. 

 These crystalline zones were of unequal density, the 

 expansion they had suffered diminishing from above 

 downward. 



"Their expansive force was, however, equal at all 

 points, their temperature everywhere bearing an in- 

 verse ratio to their density. But when by the ac- 

 cession of caloric from the inner and unliquefied nu- 

 cleus the temperature, and consequently the expan- 



137 



