CAUSES OF EARTHQUAKES. 123 



absence of all positive knowledge on the sub- 

 ject, and comparing them with the lesser phe- 

 nomena, we are ourselves able to produce by 

 various combinations of different substances, 

 that view of their nature seems most probable 

 which regards them as of a purely chemical 

 origin and character. 



Eecently a theory has been put forth, which 

 advocates the idea that earthquakes are of an 

 electrical origin, being the result of electric dis- 

 charges in the earth, passing violently through 

 beds of non-conducting substances. It has 

 hence been thought quite possible to prevent 

 them, if a metallic or other good conduct- 

 ing communication could be effected through 

 the temporary or permanent non-conducting 

 strata, so that the electric currents might find 

 a ready passage. It is singular that this idea 

 has already been carried into execution. The 

 Chevalier Vivenzio, at the latter end of the last 

 century, being self-convinced that earthquakes 

 were the result of electric currents, the free 

 passage of which was thus impeded, proposed 

 to fix metallic rods, terminating in a number of 

 points, like a brush, in the ground, to as great a 

 depth as possible. But a better method was sub- 

 sequently devised. In Naples there is a pyramid 

 erected before a church, under which is a deep 

 well, with several mouths opening about the 



