GEOLOGY. 625 



to be the laboratory of nature, and the reservoir from 

 Avhence she draws all the blessings and ills which she pours 

 upon earth; the rivers which water and the torrents which 

 ravage it, the rains which fertilize and the storms which 

 desolate it. 



The mountains are only the result of upheavals of the 

 crust of the earth caused by throes of the incandescent 

 mass which it envelops. The globe, in cooling, is neces- 

 sarily forced to contract. When the elasticity of the crust 

 has reached its farthest limits, it splits, and its fragments 

 produce eminences, the elevation of which is in direct j^ro- 

 portion to the thickness of the covering and the intensity 

 of the volcanic effort. 



In the earliest times the surface of the earth jDresented 

 no mountains, and those which first appeared were very 

 low in height. The solidified crust lacing then very thin 

 required but little effort to raise it. But in proj)ortion as 

 it became thicker the mountains acquired a proportionate 

 elevation, and in order to cleave it an effort of the most 

 prodigious kind was necessary. 



The great shocks, as we have ah'eady said, have at times 

 rent the globe almost from one pole to the other. As a 

 particular instance we may mention the upheaval which 

 formed the New World, during which the Cordilleras ap- 

 peared, stretching away from the Icy Sea to Tierra del 

 Fuego, producing the great wall which traverses the two 

 Americas. 



When we think of the ravages which are occasioned in 

 our own time by simple earthquakes, we at once conclude 

 that these cataclysms must have been accompanied by an 

 uproar and an amount of confusion, of which our minds 

 could never form but a very imperfect image. 



The birth of lofty chains of mountains has occasioned 



