204 REACTION OP THE INTERIOR OF THE EARTH 



Before we quit this important class of phenomena, which 

 I have considered not so much in its individual as in its 

 general, physical, and geological relations, I would advert 

 to the cause of the deep and peculiar impression pro- 

 duced on the mind by the first earthquake which we 

 experience, even if it is unaccompanied by subterranean 

 noise. I do not think that this impression is produced 

 by the recollection at the moment of the dreadful images 

 of destruction, which historic relations of past catastrophes 

 have presented to our imaginations : it is rather occa- 

 sioned by the circumstance that our innate confidence in 

 the immobility of the ground beneath us is at once shaken. 

 From our earliest childhood we are accustomed to contrast 

 the mobility of water with the immobility of the earth : all 

 the evidences of our senses have confirmed this belief; and 

 when suddenly the ground itself shakes beneath us, a natural 

 force of which we have had no previous experience presents 

 itself as a strange and mysterious agency. A single instant 

 annihilates the illusion of our whole previous life ; we feel the 

 imagined repose of nature vanish, and that we are ourselves 

 transported into the realm of unknown destructive forces. 

 Every sound affects us our attention is strained to catch 

 even the faintest movement of the air we no longer trust 

 the ground beneath our feet. Even in animals similar inquie- 

 tude and distress are produced ; dogs and swine are particu- 

 larly affected, and the crocodiles of the Orinoco, which at all 

 other times are as dumb as our little lizards, leave the agi- 

 tated bed of the river and run with loud cries into the forest. 

 To man, the earthquake conveys a sense of danger of which 

 he knows not the extent or limit. The eruption of a vol- 

 cano, the flowing stream of lava threatening his habitation, 

 can be fled from -, but in the earthquake, turn where he will, 



