168 COSMOS. 



that, besides the commotion of solid parts as earth-waves, 

 very different forces — as, for instance, physical forces, emana- 

 tions of gas and vapor — also assist in most cases in the pro- 

 duction of fissures. When in the undulatory movement the 

 extreme limit of the elasticity of matter set in motion (accord- 

 ing to the difference of the rocks or the looser strata) is ex- 

 ceeded, and separation takes place, tense elastic fluid may 

 break out through the fissures, bringing substances of various 

 kinds from the interior to the surface, and giving rise again, 

 by their eruption, to translatory movements. Among these 

 phenomena which only accompany the primitive commotion 

 (the earthquake) are the elevation of the undoubtedly wan- 

 dering cone of the Moya, and probably also the transporta- 

 tion of objects upon the surface of the earth.* When large 

 clefts are formed, and these only close again at their upper 

 parts, the production of permanent subterranean cavities may 

 not only become the cause of new earthquakes, as, according 

 to Boussingault's supposition, imperfectly-supported masses 

 become detached in course of time and fall, producing com- 

 motions, but we may also imagine it possible that the circles 

 of commotion are enlarged thereby, and that in the new earth- 

 quake the clefts opened in the previous one enable elastic 

 fluids to act in places to which they could not otherwise 

 have obtained access. It is, therefore, an accompanying 

 phenomenon, and not the strength of the wave commotion, 

 which has once passed through the solid parts of the earth, 

 that gives rise to the gradual and very important, but too 

 little considered enlargement of the circle of commotion.^ 



Volcanic activities, of which the earthquake is one of the 

 lower grades, almost always include at the same time move- 

 ment and the physical production of matter. In the Delin- 

 eation of Nature we have already repeatedly indicated that 

 water and hot vapors, carbonic acid gas and other mofettes, 



* Cosmos, vol. i., p. 206. Hopkins has very correctly shown theo- 

 retically that the fissures produced by earthquakes are very instruct- 

 ive as regards the formation of veins and the phenomenon of dis- 

 location, the more recent vein displacing the older formations. But 

 long before Phillips (in his "Theorie der Gange,"' 1791), Werner 

 showed the comparative ages of the displacing penetrating vein and 

 of the disrupted penetrated rock (see British Assoc. Report, 1847, 

 p. 62). 



t Upon the simultaneous commotion of the tertiary limestone of 

 Cumana and Maniquarez since the great earthquake of Cumana, on 

 the 14th December, 1796, see Humboldt's Relation Ilistorique, tome i., 

 p. 314 ; Cosmos, vol. i., p. 212 ; and Mallet, Brit. Assoc. Rejiort, 1850, 

 p. 28. 



