and the Nature of the Liquidity of Lavas. 141 
soon after was completely filled. And the cone from that time 
went on increasing in bulk and height from the effect of mmor 
eruptions, until in 1850 one of a violently explosive character 
Fig. 3.—Crater of Vesuvius after the Eruption of October 1822. 
opened the two deep craters on its summit, of which I have 
already spoken. The more recent eruption of May last, being 
confined chiefly to a prodigious efflux of lava from the outer side 
of the cone, unaccompanied by any extraordinary explosive bursts 
from the summit, has not altered materially the form impressed 
upon it in 1850. 
It is thus seen that within the last 100 years the cone of 
Vesuvius has been five several times gutted by explosive eruptions 
of a paroxysmal character, viz. in 1794, 1822, 1831, 1839, and 
1850 ; and its central craters formed in this manner as often 
gradually refilled with matter, to be again in due time blown 
into the air. Meanwhile the old external crater of Somma is itself 
becoming choked up by the accumulation of all the lava-streams 
and fragmentary matter that are expelled towards the northern 
and outer side of the cone. It would be, therefore, in exact ac- 
cordance with the habit of this voleano (as of volcanic mountains: 
in general), if, after some further period either of quiescence or 
of moderate activity, the entire cone of Vesuvius should be blown 
up by a more than ordinarily violent paroxysm, and the crater 
of Somma itself reformed. 
With this well-authenticated history of the mountain within 
our knowledge, would it not be wholly unphilosophical to deny 
(except upon such grounds of impossibility as have never been 
adduced) that the larger containing crater in the case of Vesuvius 
(and the argument applies to other similar voleanic mountains) 
had the same origin as the smaller contained ones; and that the 
external cones were produced in the same manner as the internal 
and similarly constituted ones? And therefore those who refuse 
