32 



islands of Mexico, of Guatemala, and of the 

 table-land of Quito ; when we examine either 

 the reactions of these different systems of volca- 

 noes on one another, or the distance to which, 

 by subterranean communications, they at the 

 same moment shake the Earth. 



The study of volcanoes presents two very 

 distinct branches ; the object of one, simply 

 mineralogical, is the examination of the stony 

 strata, altered or produced by the action of 

 fire ; from the formation of the trachytes or 

 trap porphyries, of basalts, phonolites, and dole- 

 since the sixteenth century, has made it's appearance alter- 

 nately in Palma, Teneriffe, and Lancerota. Auvergne pre- 

 sents us with a whole system of volcanoes, the action of 

 which has ceased ; hut in the middle of a system of active 

 volcanoes, for instance, in that of Quito, we must not con- 

 sider as an extinguished volcano a mountain, the crater of 

 which is obstructed, and through which the subterraneous 

 fire has not issued for ages. Etna, the Eolian isles, Vesu- 

 vius, and Epomeo ; the peak of Teyde, Palma, and Lance- 

 rota - } St. Michael, la Caldiera de Fay a], and Pico j St. 

 Vincent, St. Lucia, and Guadaloupe ; Grizava, Popocatepec, 

 Jorullo, and la Colima ; Bombacho, the volcano of Grana- 

 da, Telica, Momotombo, Isalco, and the volcano of Guate- 

 mala j Cotopaxi, Tunguragua, Pichincha, Antisana, and 

 Sangay, belong to the same system of burning volcanoes; they 

 are generally ranged in rows, as if they had issued from a 

 crevice, or vein not filled up ; and, what is very remarkable, 

 tlieir position is in some parts in the general direction of the 

 Cordilleras, and in others in a contrary direction. (Essai 

 politique sur le Mexique, torn, 1, p. 253.) 



