174 REACTION OF THE INTERIOR OF THE EARTH 



a simple transport over the earth's surface ? As in 

 nature effects are reproduced on the return of similar 

 conditions, we ought unhesitatingly to mention even 

 incomplete observations in order to direct the attention 

 of future observers to special phenomena. 



It is not to be forgotten that in most cases of the 

 production of fissures, the earth-wave or undulation, by 

 which the solid parts are agitated, is associated, accord- 

 ing to my experience, with a concurrent action of very 

 different forces, manifested in emanations of gases and 

 vapours. If, in the undulatory movement, the extreme 

 limit of the elasticity of the material (of the different 

 kinds of rock or loose earthy strata) is overpassed, and 

 rupture or separation ensues, elastic fluids in a state of 

 tension may escape through the openings thus formed, 

 bringing from the interior to the surface different sub- 

 stances, whose outburst may again become in turn a 

 cause of fresh translatory movement. To the class of 

 these merely accompanying phenomena of the primary 

 agitation or earthquake, belongs the elevation of uncon- 

 testedly moving Moya cones; and, probably, also the 

 transport of objects on the surface of the earth. ( 244 ) 

 When, in the formation of great fissures, they close again 

 in their upper portions only, the subterranean cavities 

 thus produced may not only become the cause of fresh 

 earthquakes, inasmuch as, according to Boussingault's 

 conjecture, ill-supported masses become in time detached, 

 and, in sinking, cause commotion, but we may also 

 conceive it possible that in the fissures opened by earlier 

 earthquakes, elastic fluids may become active in occa- 

 sioning fresh earthquakes in places to which they for- 

 merly had no access. It would thus be the accompanying 



