570 THE UNIVERSE. 



servations of Buffon and Cuvier, partly the calculations of 

 Cordier, La Place, and Fourier. 



The globe on fire, and launched into space, necessarily 

 obeyed the laws of the radiation of heat, and when after 

 a long succession of ages it had sufficiently cooled down 

 its surface became solidified, and constituted the primitive 

 crust. 



When this cooling down had made sufficient progress, 

 the vapours from the earth, an immense atmosphere of 

 which envelojDed the globe, became condensed and poured 

 over the surface in torrents of rain. Gleams of lightning 

 and incessant peals of thunder accomj^anied these impos- 

 ing scenes of the birth of our globe, of which our imagina- 

 tion will never yield us more than an imperfect image. 

 Such was the origin of the first seas. 



At the same time that in the course of ages the crust 

 of the earth augmented in thickness, the cooling down, 

 by contracting the globe, forced its envelope to yield and 

 break. These efforts produced the mountains which now 

 roughen its surface.^ 



Whilst the crust of the earth was yet thin, a slight 

 cftbrt of the central heat sufficed to rupture it, but this 

 only produced insignificant elevations. AVhen this crust 

 had acquired sufficient firmness and thickness, its rupture, 

 inasmuch as it demanded much greater force, was only 

 effected by means of the most violent plutonic movements; 

 it Avas then that the Cordilleras rose into the clouds. 



The upheaval of each mountain chain was necessarily 

 accompanied by enormous perturbations in the level of 



1 Some of these -upheavals only date from a recent period ; some are even 

 contemporaneous with the existence of man. Such for instance is, according to 

 M. Beudant, the upheaval which gave rise to Etna, Vesuvius, and Stromboli ; 

 and those which formed Monte-Nuovo, and JoruUo, the great volcano of Mexico, 

 doubtless belong to the same class. — Tr. 



