Volcanos. 1 33 



North America into California, Mexico, Guatimala, Nicaragua, 

 Panama, and the vast volcanic range of the South American Cor- 

 dilleras, even to Terra del Fuego. If, as appears most proba- 

 ble, such trains of volcanic vents indicate fissures, broken 

 through the superficial strata by subterraneous expansion, what 

 a prodigious compound fracture in the crust of our globe does 

 this immense chain of volcanos disclose to us. In these systems, 

 some few vents remain occasionally active, others closed, the 

 former acting as safety-valves to the neighboring districts. In 

 case of their permanent obstruction, some fresh vents must be 

 produced, or some former orifice re-opened; while violent 

 earthquakes, and elevations of the neighboring strata, will pre- 

 cede or accompany this change. The author then dwells on the 

 appearances in the constitution of the known surface of the 

 earth, which indicate numerous and forcible elevations of stra- 

 ta, by subterranean expansions, more particularly in the elevated 

 or mountainous districts, which according to him, are those points 

 or lines that have suffered the maximum of elevation, from the 

 extreme developement of the expansive process beneath them. 

 But since, as has been stated above, and as is shown to be conform- 

 able to observation from a variety of instances, the existence of 

 active volcanos obviates the occurrence of such extensive eleva- 

 tions of the superficial strata, by letting off, through fissures in 

 these strata, the superfluous caloric, which would otherwise ac- 

 cumulate and produce successive powerful expansions in the 

 great bed of lava beneath them, we must expect to find such spi- 

 racles to be frequent in the lower levels of the globe's surface, 

 and rare in those higher, — and this is precisely true to the letter ; 

 for we know of very few volcanic vents in the interior of the 

 continents, or amongst mountain ranges, while they rise in vast 

 numbers from the depths of the ocean. If the Andes are urged 

 as a striking exception, it is replied, that this great range is it- 

 self composed almost wholly of volcanic, or at least, pyrogenous 

 rocks, which, like iEtna, Teneriffe, &.c. have swelled to their 

 immense height by the accumulated ejections of very productive 

 vents. 



"But, notwithstanding the distance usually interposed between 

 the principal trains of volcanic vents, and the elevated continen- 

 tal ranges, Mr. Scrope thinks he perceives a frequent and re- 

 markable parallelism in their direction. Thus the volcanic trains 

 of France, Germany, and Italy, run decidedly parallel to the op- 

 posite ranges of the Alps and Apennines ; that immense chain 

 which encircles the Pacific, is almost uniformly parallel to the 

 neighbouring high lands of Asia and America, &c. and he is thus 

 led to suppose, that the creation of fissures of elevation, and the 

 protrusion through them, of crystalline rock, chiefly in a more or 



