128 E AMBLES OF A NATURALIST. 



ther in masses cannot possess any great stability. 

 The sinking in, which is visible on the margins of the 

 Piano del Lago and at other points, sufficiently 

 proves how deficient in solidity is this kind of frame- 

 work. When the subterranean furnaces are kindled 

 and the rocks are fused, and an enormous quantity 

 of gas liberated, an outlet must be obtained at some 

 point or other. And if the crater is slow in opening, 

 and the passages of communication should be closed, 

 why should not the boiling lava raise up the vault 

 which accidentally confines it in the same manner as 

 the lava of Vesuvius, acting alone and without any 

 shocks, upheaved before our eyes a hillock of several 

 feet?* 



The difference of thickness of the strata cannot 

 be adduced in opposition to these conclusions. Is 

 the earth's crust, on which we dwell, and in which 

 the basins of our seas are hollowed out, in reality so 

 solid as we are inclined to imagine ? We will pause 

 to consider this question. 



Entire provinces have been gradually and con- 

 tinuously raised ; as, for instance, a portion of Scan- 

 dinavia. In other cases they have been suddenly 

 elevated above the ordinary level, as was the case in 

 1822 with the territories of Valparaiso and Quintero. 

 Considerable islands issuing from the bottom of the 



* During the whole time that M. Blanchard and myself remained 

 within the crater, that is to say, for more than three hours, we 

 experienced nothing that resembled an earthquake. It was the 

 absence of every indication of this convulsion which enabled us to 

 enjoy entire security, and to observe without the least uneasiness 

 the beautiful eruption which was so well adapted for a subject of 

 study. 



