OF VOLCANOS. 221 



lava-currents, properly so-called, in the Euganean hills and 

 the Siebengebirge near Bonn ; and at other times the same 

 study describes to us volcanos arranged in single or double 

 lines extending through many hundred leagues in length, 

 these lines being either parallel to the direction of a great 

 chain of mountains, as in Guatimala, in Peru, and in Java, 

 or cutting it transversely or at right angles, as in tropical 

 Mexico. In this land of the Aztecs the fire-emitting 

 trachytic mountains are the only ones which attain the 

 elevation of the lofty region of perpetual snow ; they are 

 ranged in the direction of a parallel of latitude, and have 

 probably been raised from a fissure 420 English geographical 

 miles long, traversing the continent from the Pacific to the 

 Atlantic Ocean. 



These assemblages of volcanos, whether in rounded 

 groups or in double lines, show in the most conclusive 

 manner that the volcanic agencies do not depend on small 

 or restricted causes, in near proximity to the surface of the 

 earth, but that they are great phenomena of deep-seated 

 origin. The whole of the eastern part of the American 

 continent, which is poor in metals, is, in its present state, 

 without fire-emitting mountains, without masses of trachyte, 

 and perhaps even without basalt containing olivine. All the 

 American volcanos are on the side of the continent w^hidi 

 is opposite to Asia, in the chain of the Andes which runs 

 nearly in the direction of a meridian, and extends over a 

 length of 7200 geographical miles. 



The whole plateau or high-land of Quito, of which 

 Pichincha, Cotopaxi, and Tunguragua form the summits, 



