and the Nature of the Liquidity of Lavas. 133 
the sides of the mountain and of its upper part ; and the weakest 
part, whichever it is, will give way, and be blown up. 
Sir Charles’s second reason is, that a sufficient amount of 
conglomerates is not to be seen on the mountain slopes around 
the Val di Bué, to account for the vacuity. But, besides that 
he himself speaks of “ enormous masses of scoriz on the flanks 
of Etna,” it should be remembered that the aériform explosions, 
when long continued, triturate the ejected matters, owing to 
their repeated fall into and rejection from the crater, to such a 
degree as to reduce the greater part at length to an impalpable 
powder, which is carried by the winds to a distance, sometimes 
of hundreds of miles, and spread in a thin layer over an enor- 
mous area of sea or land. And, moreover, the larger the dimen- 
sions of any crater, the more powerful and enduring will have 
been, in all probability, the explosions, and the more thoroughly 
triturated, during the process of its gradual enlargement, would 
be the fragments thrown up by them. 
I remember being exceedingly surprised, after the termination 
of the Vesuvian eruption of 1822, forming a continual fountain 
of stones and ashes some miles in height, lasting through 
twenty days, and in the end completely gutting the mountain, 
to find that the prodigious amount of fragmentary matter 
thrown out from the crater had coated the outer slopes of the 
mountain only to an average thickness of a foot or two at most. 
But then the ashes which day by day were reduced to a finer 
and at length to an impalpable powder, so fine as to penetrate 
the closest rooms in the houses of Naples, were borne to vast 
distances by the winds. Much, too, was carried down into the 
plain, or the sea below the mountain, by the torrents of rain 
(producing lave di fango, or mud-lavas), such as overwhelmed 
Herculaneum, and which accompanied, as usual, the paroxysmal 
eruption of 1822. 
Indeed, if we consider the statements adduced on good 
authority, of the prodigious distances to which ashes, and even 
large fragments of lapillo and of pumice, have been occasionally 
borne away from some of the volcanoes of South America and 
the Pacific (as, for example, in the eruption of Coseguina in 
1835, and of Galongoon in 1822),—distances of more than a 
thousand miles (a large segment of the circumference of the 
globe), the whole of which intermediate space must have been 
strewn with them (and, in the first of these instances, it is 
said, to the depth of ten feet at the distance of twenty-four miles 
from the volcano), we may well conceive that eruptions productive 
of such an enormous amount of ejected matters may (nay, must) 
have blown into the air entire mountains of a magnitude far ex- 
ceeding that of Vesuvius and Somma itself, or the bulk of matter 
