48 Natural History of Volcanos and Earthquakes. 



were suddenly raised, and then sunk again. Yon HofP has 

 also related the circumstance, that the shocks of earthquakes are 

 most common in the same direction as that of the basaltic masses 

 themselves, and around a certain distance on either side of the 

 line in which they occur. 



On the other hand, there are many instances of the countries 

 of Europe having been agitated in all directions, without having 

 been influenced by the mountains. Thus, earthquakes have ex- 

 tended from Upper Italy across the Alps to Switzerland. That 

 at London (19th March 1750) followed the direction from W. to 

 E., although the direction of the mountains in England is from 

 S. S. W. to N. N. E. &c. Sometimes the earthquakes originate 

 from a common centre in a radiating direction on all sides. That 

 of Lisbo7i, (1755,) that in Calabria (1783,) and that at Lima 

 (1746,) &c., ofler instances of this kind. 



With regard to the earthquakes in South America, it has been 

 observed that they occur principally in the mountainous coun- 

 tries. The cause which produces them, seems, as Boussingaultf 

 believes, to be so constantly in operation, that, if all the earth- 

 quakes, which are felt in the inhabited countries of America, 

 could be noted, the earth would be found to quake nearly with- 

 out intermission. These frequent movements of the ground of 

 the Andes, and the slight coincidence between these convulsions 

 and the volcanic eruptions, induce us to adopt the opinion of 

 Boussingault, that the former are, for the most part, independent of 

 the latter. He ascribes the greatest number of the earthquakes in 

 the A7ides to the sinking of rocks in the interior, which is a con- 

 sequence of the former elevations of these chains of mountains. 

 In favor of these suppositions, he affirms that these gigantic rocks 

 have been thrown up, not in a doughy, but in a solid and frag- 

 mentary state, but that the consolidation of these fragments of 

 crystalline rocks might not at first have been so firm, as not 

 to admit of some sinking after the elevation. He refers to the 

 Indian tradition which preserves the memory of the sinking of 

 the celebrated mountain of Capac-Urcu, near Riobamba, the 

 name of which signifies the chief, i. e. the highest, of all the 

 mountains near the Equator. It is said that the top of this 



* Gescbichte der Vertlnderungen der Erdoberflache, t. ii. 

 t Annal. de Chim. et de Pliys., t. Iviii, p. 83. 



