48. ; Natural History of Volcanos and Earthquakes. 
were suddenly raised, and then sunk again. Von Hoff* 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 Hngland is from 
Ss. s W.to N.N. E. &c. Sometimes the earthquakes originate 
from a common centre in a radiating direction on all sides. ‘That 
of Lisbon, (1755,) that in Calabria (1783,) and that at Lima 
(1746,) &c., offer instances of this kind. : 
With deed 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 Boussingaultt 
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 Andes 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, ¢. e. the highest, of all the 
mountains near the Equator. It is said that the top of this 
apr: 
tail 
* Geschichte der Verinderungen der Erdoberflache, t. il. 
t Annal. de Chim. et de Phys., t. lviii, p. 83. 
