VOLCANOES. 
rates without much violence, and yet if tlie 
vapour thus generated is confined by sn- 
periiicumbent earth, or loeks, its struggles 
for a vent must occasion the violent disrup- 
tion of those parts ; the event is different 
on pouring water on melted tin, which is 
the only metal that is separated by this 
means so as to render it a dangerous ope- 
ration to the experimentalist. 
Spallanzani concludes many curious and 
interesting observations derived from expe- 
rience, by saying, “ from this series of ex- 
periments I think we are authorised to 
conclude, that when a quantity of water 
falls on the burning crater of a volcano, it 
has not the power of producing explosions ; 
but that the latter on the contrary are 
very violent when the water penetrating 
below, reaches the conflagration ; when 
suddenly reduced to vapour by the beat, it 
finds no room for its dilatation ; or when it 
insinuates itself laterally among the liquified 
matters; of which we have a satisfactory 
proof in the explosion of the lava, violently 
forced from the containing vessel, on the 
introduction of water into a cavity made in 
it.” 
From what has been already said, a tole- 
rable conception may be formed of the 
probable causes of volcanic eruptions, it 
now remains for us to add a concise narra- 
tive of their visible phenomena, and for this 
purpose we find ample Materials furnished 
by Spallanzani, whose ascent of Stromboli 
deserves every praise for its courage, though 
we cannot help condemning him for the ex- 
ercise of very daring temerity. The visit 
we allude to was made in 1788, when the 
appearance of the mountain was bifurcated, 
and the crater situated at some distance 
from the summits, from both of which the 
operations within it are distinctly visible, 
and from those the height of the ejections 
may be ascertained, with tolerable accuiacy. 
During violent internal agitation the matter 
appears to ascend half a mile and more, but 
when the mountain is in actual eruption, 
the scattered fragments prove, that the im- 
pelling force is very greatly increased. Af- 
ter having attentively examined the crater 
from the summit above alluded to, Spallan- 
zani approached the crater, where he found 
that the explosions succeeded each other so 
rapidly, that they might almost be said to 
occur without any intervals of quiet, but 
they varied in their force ; the matter, in 
some instances, not rising more than fifty 
feet, and falling again into the crater ; and 
in others it was elevated half a mile ; the 
sounds, consequently, are proportionably 
loud, or the reverse, and resemble a hissing 
noise ; the fragments of lava were actually 
fluid during their progress, which was evi- 
dent from their globular shape, and becom- 
ing hard before they fell upon the sides of 
the mountain, that foi'm is preserved. 
The exhalations exhibited a thick cloud 
several miles in extent, which wore strongly 
impregnated with sulphur ; this cloud was 
impenetrable by the beams of the sun, and 
appeared very black in the midst, but w'hite 
on the edges, and was, in all probability, a 
mile in depth. The vapour thus floating 
from the mountain was derived from three 
distinct sources, though doubtlessly pro- 
duced by the same cause in the first in- 
stance : when an ejection of lava took 
place, it was always accompanied by a 
cloud of grey smoke from the crater ; to 
the west of that spot were a number of ob- 
scure apertures, each of which sent forth a 
volume of similar vapour; and to the east, 
a vast cavern emitted a column at least 
twelve feet in diameter, extremely black 
and dense. 
“ Not satisfied with the observations I 
had already made,” observes Spallanzani, 
“ my curiosity impelled me to attempt fur- 
ther discoveries. From the pointed rock 
on which I stood, I could only see the edges 
of the inside of the crater, I considered, 
therefore, whether it might not be po.ssible 
to obtain a sight of the lower parts like- 
W'ise ; and, looking round me, I perceived 
a small cavern hollowed in the rock, very 
near the gulph of the volcano, into which 
the rock above prevented the entrance of 
any burning stones, should they be thrown 
so far. It was likewise so elevated, that 
from it the crater was open to my view. I 
therefore hastened to take my station in 
this cavity, taking advantage of one of the 
very short intervals between the eruptions. 
To my great satisfaction, my expectations 
were completely fulfilled ; I could here look 
dow'n into the very bowels of tlie volcano, 
and truth and nature stood as it were un- 
veiled before me." Thus situated in pro- 
bable safety, the intrepid Spallanzani saw 
the following wonders. 
The crater he found to be of a circular 
form, with edges composed of a chaos of 
sand, scoriae, and lava; and he imagined 
the circumference to be about three hun- 
dred and forty feet. Similar to all other 
craters, that of Stromboli assumes the shape 
of a truncated inverted cone, the sides of 
which, from east to south, were gently in- 
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