170 COSMOS. 



of 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, la 

 ammonia, and sulphuretted hydrogen, certainly does not 

 sufficiently replace) has led the celebrated originator of 

 this hypothesis to abandon it of his own accord. 13 



According to a third view, that of the highly endowed 

 South American traveller, Boussingault, a deficiency of 

 coherence in the trachytic and dolentic masses which form 

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

 garded 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 semifluid state, but 

 have been thrown up and piled on one another when 

 fectly hardened, in the form of enormous, shai 

 fragments. In an elevation and piling of this description, 

 large interstices and cavities have necessarily been pro- 

 duced ; so that by sudden sinking, and by the fall of solid 

 masses which are too weakly supported, shocks are pro- 

 duced. 14 



Upon the difficulty of a theory founded upon the penetration of water, 

 Bee Hopkins, Brit. Assoc. Rep. 1847, p. 38. 



12 According to the beautiful analyses made by Boussingault, on the 

 margins of five craters (Tolima, Purace, Pasto, Tuqueras, and Cumbal), 

 hydrochloric acid is entirely wanting in the vapours poured forth by 

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

 Chimie, tome lii, 1833, pp. 7 and 23). 



13 Cosmos, vol. i, p. 234, Boon's edition. Whilst Davy, in the most 

 distinct manner, gave up the opinion that volcanic eruptions are a con- 

 sequence of the contact of the metalloid bases with water and air, he 

 still asserted that the presence of oxidizable metalloids in the interior 

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

 commenced. 



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

 Cordillera of the Andes to falls produced in the intei-ior of these moun- 

 tains by the subsidence which takes place, arid which is a consequence 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 ele- 

 vated masses ot 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 interior movements in the fragmentary 

 masses" (Boussingault, /Siw les TremUcmcm de Terre des Andes, in 



