348 Prof. Bischof on the Natural History of 



beyond the immediate influence of the impelh'ng force. In a 

 former place, I have also shewn, that the seat of volcanic action 

 may be looked for at depths far less than Stukeley supposes. 

 But there is no reason to believe that earthquakes could go on 

 at greater depths than volcanic actions. Supposing that the in- 

 terior of the earth is still fluid, and that rents conducting water 

 extend from the surface to the fluid nucleus, it is easy to con- 

 ceive that the actions of the steam may be felt at very remote 

 distances. 



We have already pointed out the close connection which 

 exists between earthquakes and volcanic eruptions. Von Hum- 

 boldt, in his travels near the Equator, gives several examples of 

 this. It may not be superfluous to refer here to what this il- 

 lustrious philosopher asserts generally with regard to these phe- 

 nomena, at the end of the 4th chapter of the ^d volume of 

 Tart I. Book 2.* 



Every thing seems to shew that earthquakes are caused by 

 the effort of elastic fluids seeking an outlet. On the coasts of 

 the South Sea their action is often communicated almost in- 

 stantaneously from Chili to the Gulf of Guayaquil, a distance 

 of 600 geographical miles ; and, what is very extraordinary, 

 the shocks seem to be so much the stronger the greater the 

 distance from the active volcanos. The granite mountains of 

 Calabria^ the limestone chain of the Apennines, the county of 

 Pignerol, the coasts of Portugal and Greece, Peru, and the 

 continent of America, furnish striking proofs of this assertion.-f* 

 It might be supposed that the earth would be more violently 

 shaken, the fewer the openings on the surface which communi-, 

 cate with the interior. At Naples and at Messina, at the footj 

 of Cotopaxi, and the Tunguragua, earthquakes are dread( 

 only when vapours and flames do not issue from the mouth 

 the volcano. In the kingdom of Quito, the great catastropl 

 of Riohamba led many well informed persons to believe the 

 this unfortunate country would be less often disturbed if tl 

 subterranean fire would succeed in destroying the dome of poi 



* See also what Von Bucli says on Vesuxius. Geognosti§che Beobacht. 

 vol. ii. p. 129. 

 t Fleuriau do Bellevue, Jouru. de Pliysique, t. Ixii. p. 261. 



