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VOLCANOES. 
it docs not chan!>e the order and manner of 
bcinff, of the constituent parts of the lavas. 
Wlien they cease to flow, they resume, like 
metals, the grain, texture, and all the cha- 
racters of their primitive base ; effects 
which we cannot produce upon stones in 
our furnaces, since we know not how to 
soften them by fire, without changing the 
manner in which they are aggregated. The 
fire of volcanoes has not that intensity which 
is supposed, and produces its effects rather 
by the extension and duration of its action 
than by its activity.” 
Arguing uporr these various facts, and re- 
marks of his own, leading to the same point, 
Spallan/ani candidly acknowledges, that he 
liad been more than once inclined to be- 
lieve, that our fires possessed more energy 
than those of volcanoes ; a number of expe- 
riments, however, induced him to say, that 
‘‘ these tacts prove, first, that it is not al- 
ways tnie, that yolcanic flies are insuffi- 
cient for the fusion of shorls ; secondly, 
by the vitrification of the garnets, they con- 
firm the powerful activity of those fires ; 
thirdly, that those fires operate in a man- 
ner ill some measure unknown to us ; since, 
at the same time that they vitrify the gar- 
nets, they leave the base, in which they are 
included in a state perfectly recognizable, 
notwithstanding that the former are refrac- 
tory to the fire of the furnace, while the 
latter is easily fusible.” It has been a ge- 
nerally received assertion, that volcanoes 
emit flame during eruption, and that flowr 
iiig lavas are attended by the same accom- 
paniment of fire ; this supposition is erro- 
neous, as may he proved by referring to 
the works of Serao, Father Torre, Bottis, 
and Sir William Hamilton, all of whom will 
be found to liave omitted the observation 
of flames. The first expressly says of the 
lavas of Vesuvius, “ that when seen by 
niglit, at any distance, they emit a light, 
npt shining, like a bright flame, but of a 
dead kind, like that of red-hot substances 
which burn without flame and the last 
mentions, that he has “observed upon 
mount Vesuvius, that soon after a lava has 
borne down and burned a tree, a bright 
flame issues from its surface ; otherwise I 
have never seen any flame attending an 
eruption adding, that the light reflected 
on tlie smoke, as it rises from the crater, by 
the raging of the fire in the gulph beneath, 
is frequently mistaken for flame. Spallan- 
gani confirms the opinion of tliese accurate 
ghservers, and declares he never saw flame 
VOL. yi. 
in, or proceeding from, any of the craters 
he examined. 
Fanjas thought it not improbable that 
fire united with water may produce some of 
those combinations of which we know not 
the origin ; he says on this subject, “ I al- 
most incline to be of opinion, that the 
aqueous fluid, raised to a degree of ebulli- 
tion and incandessence, of which our feeble 
furnaces can give us no idea, sometimes 
concurs with the inactive and concentrated 
fire which exists in the immense volcanic 
caverns, and that from this concurrence 
results a multitude of combinations hitherto 
unknown to us, which take effect on the 
stones and earths that remain perhaps whole 
ages in these burning gulphs, where the 
fire, intent to destroy, has for its adversary 
the water, which incessantly creates and op- 
poses to it all the forms and modifications 
of which the matter is susceptible.” 
It will now be necessary to mention some 
of the effects of gas, in the operations of 
these fierce internal fires : it is well known 
that their violent efforts to reach the sur- 
face of the liquified masses contained in cra- 
ters causes it to rise suddenly from the bot- 
tom, completely filling their whole circum- 
ference, and at length forcing it over the 
sides in destructive streams, which over- 
whelm in their passage every object, either 
natural or artificial. Spallanzani made ten 
distinct experiments, in order to obtain 
some idea of the nature and effects of gas 
as exhibited by volcanoes ; for this purpose 
he made use of different lavas, enamels, and 
glasses, ejected from them, and the conse- 
quence was, a conviction that the bubbles 
and inflations of various dimensions, ob- 
servable in these substances, are not pro- 
duced by the action of any permanent gas, 
“ but by that of an aeriform fluid, produced 
by the excessive attenuation of those same 
products, in consequence of heat.” Dr, 
Priestley made similar experiments, which 
differed in some degree from those related by 
the above celebrated Italian naturalist. The 
doctor fused 4^ oiinces of lava from Iceland 
in a sand-stone retort, and obtained twenty 
measures of air, half of which, at the com- 
mencement of the process, was carbonic 
acid gas, and thp remainder, in purity 1.72, 
extinguished a candle ; between the inter- 
stices of this lava was a sand, which the 
operator could not separate from it. Five 
ounces and an half of Vesnvian lava pro- 
duced thirty measures of air, with a slight 
appearance of carbonic acid gas, the rest 
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