164 COSMOS. 



the internal lava; and the deficiency, or, at all events, 

 very rare occurrence of burning hydrogen gas during the 

 eruption (which the formation of hydrochloric acid,* am- 

 monia, and sulphureted hydrogen certainly does not suffi- 

 ciently replace), has led the celebrated originator of this 

 hypothesis to abandon it of his own accord, f 



According to a third view, that of the highly-endowed 

 South American traveler, Boussingault, a deficiency of co- 

 herence in the trachytic and doleritic masses which form 

 the elevated volcanoes of the chain of the Andes, is regard- 

 ed as a primary cause of many earthquakes of very great 

 extent. The colossal cones and dome-like summits of the 

 Cordilleras, according to this view, have by no means been 

 elevated in a soft and semi-fluid state, but have been thrown 

 up and piled on one another when perfectly hardened, in 

 the form of enormous, sharp-edged fragments. In an ele- 

 vation and piling of this description, large interstices and 

 cavities have necessarily been produced ; so that by sud- 

 den sinking, and by the fall of solid masses which are too 

 weakly supported, shocks are produced. J 



that the radicals of silica, alumina, lime, and iron are combined with 

 chlorine in the interior of the earth," and the penetration of sea-wa- 

 ter does not appear to him to be improbable tinder certain conditions 

 (p. 419, 420, 423, and 426). Upon the difficulty of a theory founded 

 upon the penetration of water, see Hopkins, Brit. Assoc. Rep., 1847, p.38. 



* According to the beautiful analyses made by Boussingault on the 

 margins of five craters (Tolima, Purace, Pasto, Tuqueras, and Cum- 

 bal), hydrochloric acid is entirely wanting in the vapors poured forth 

 by the South American volcanoes, but not in those of Italy (Annales 

 de Chimie, tome lii., 1833, p. 7 and 23). 



f Cosmos, vol. i., p. 236. "While Davy, in the most distinct man- 

 ner, gave up the opinion that volcanic eruptions are a consequence of 

 the contact of the metalloid bases with water and air, he still assert- 

 ed that the presence of oxydizable metalloids in the interior of the 

 earth might be a co-operating cause in volcanic processes already com- 

 menced. 



| Boussingault says: "I attribute most of the earthquakes in the 

 Cordillera of the Andes to falls produced in the interior of these 

 mountains by the subsidence which takes place, and which is a conse- 

 quence of their elevation. The mass which constitutes these gigantic 

 ridges has not been raised in a soft state ; the elevation did not take 

 place until after the solidification of the rocks. I assume, therefore, 

 that the elevated masses of the Andes are composed of fragments 

 heaped upon each other. The consolidation of the fragments could 

 not be so stable from the beginning as that there should be no 

 settlements after the elevation, or that there should be no inte- 

 rior movements in the fragmentary masses" (Boussingault, Sur les 

 Tremblemens de Terre des Andes, in Annales de Chimie et de Phy- 

 sique, tome Iviii., 1835, p. 84-86). In the description of his mem- 



