Natural History of Volcanos and Earthquakes. 43 



to the force of elastic fluids, brought forward, in support of their 

 opinion, the total cessation of earthqualces in the island of Eu- 

 boa, after the opening of a chasm in the Lelantic fields.* 



The intimate connection of earthquakes with volcanos is not 

 less clearly proved by the direction which the former take. With 

 the assistance of a simple instrument (the sismograph) invented 

 by Cacciatore, and erected at Palermo, it was found in twenty- 

 seven cases that the shock was propagated in a fixed linear di- 

 rection, which coincided remarkably with the cardinal points. 

 In nineteen cases the shocks were transmitted in a direction from 

 east to west, corresponding with the situation of Mount Etna, 

 the source of all these subterranean concussions, which lies di- 

 rectly to the east of Palermo. In four cases it was from south 

 to north ; but, for want of corresponding observations, the seat of 

 these shocks cannot be determined ; and it certainly does not 

 seem to have been the effect of chance, that three shocks, which 

 were felt on the 9th February, 30th June, and 2d July 1831, 

 traveled from the south-west to the north-east : for it was pre- 

 cisely in that direction, at a distance of about 70 Italian miles, 

 that the small new volcano suddenly appeared in the sea, prob- 

 ably on the 2d July. The two latter shocks were also the very 

 same that were felt with greater force at Sciacca, on the southern 

 coast, opposite to the new volcano.f 



On the other hand, BoussingaultJ asserts that the most mem- 

 orable earthquakes in the New World, which ravaged the towns 

 of Latacunga, Riohamba, Honda, Caraccas, Laguayra, Merida, 

 Barquisirneto, &c., do not coincide with any well established 

 volcanic eruption. The oscillation of the surface, owing to an 

 erruption, is, as it were, local ; whilst an earthquake, which is 

 not subject (at least apparently) to any volcanic eruption, extends 

 to incredible distances, in which case it has also been remarked 

 that the shocks most commonly follow the direction of chains 

 of mountains. 



In favor of the hypothesis, that earthquakes are produced by 

 aqueous vapor|| penetrating to great depths, the following circum- 



* Strabo, lib. i, ed. Oxon. 1807, t. i, p. 85. 

 t F. Hoffman in Poggend. Ann. t. xxiv, p. 63. 

 X Annal. de Chirn. etde Phys. t. Iviii, p. 83. 



II A remarkable case which has taken place at the iron-foundery at Sayn, proves, 

 that shocks of the earth may be several times repeated by the effect of elastic flu- 



