498 
that by means of heat, of water, and of 
the oxygen of the air, it is changed 
into peroxidé, which collects, and 
assumes. a crystalline form during pre- 
cipitation. If we suffer a stream of 
chlorine at the temperature of about 
400° to pass over a steel harpsichord- ' 
wire, the wire immediately becomes 
incandescent, but not nearly so soon as 
with oxygen. The perchloride of iron 
is very yolatile; it crystallizes on 
cooling into very small light flakes, 
which ‘instantly fall into deliquescence 
on exposure to. the air. It heats so 
strongly with water, that I should not 
be surprised, if, in a large mass, and 
with a proportional quantity of water, 
it should become incandescent. I 
make this observation in order to sug- 
gest to my readers, that, if silicium and 
aluminium really existed in the bowels 
of the earth in the state of chloride, 
they might produce a much higher 
temperature upon coming in contact 
with water, since their affinity for 
oxygen is much greater than that of 
iron. 
If, as can hardly be doubted, sul- 
phurous acid be really disengaged from 
volcanos, it is very difficult to form an 
Opinion of its true origin. Whence 
should it derive the oxygen. necessary 
to its formation, unless it be the result 
of the decomposition of some sulphates 
by the action of heat; and of the affinity 
of their bases for other bodies? This 
Opinion appears to me to be the most 
probable; for I cannot conceive, from 
what is known of the properties of 
sulphur, that itis an agent in volcanic 
fires, 
Klaproth and M. Vauquelin have 
conjectured that the colour of basalt 
might be ascribed to carbon; but, to 
confute this supposition, we need only 
remark, that when a fusible mineral, 
even, if it contain less than ten hun- 
drediths of oxide of iron, is heated to a 
high temperature in a crucible made 
of clay and pounded charcoal (creuset 
brasque), a considerable quantity of 
iron is produced, as Klaproth- has 
shown in the first volume of his Essays. 
Messrs. Gueniveau and Berthier: as- 
sert, moreover, that there remains no~ 
more than from three to four hun- 
dredths of oxide of iron in the scoriz 
of highly-heated furnaces. _ Now, as 
lava contains a large proportion of 
iron, and as the basalt which has been 
analysed contains from fifteen to 
twenty-five hundredths of the same 
substance, it is not probable that 
Theory of ¥: olcanos, 
by M. Gay-Lussac. ‘{Jan. 1, 
carbon could exist in the presence of 
so large a quantity of iron without re- 
ducing it.* 
Is it not possible that, if hydrogen:be 
disengaged from volcanos, metallic 
iron, the oxides of which have the 
property of reducing at a high tempe- 
rature, may be found in Java? It isat 
least certain that it does not contain. 
iron in the state of peroxide; for lava 
acts powerfully on a magnetized bar, 
and the iron it contains appears to be 
at the precise degree of oxidation 
which alone is determinable by water ; 
that is to say, in the state of deu- 
toxide, Ihave already shown, that, if 
hydrogen be mixed with many times its 
volume of aqueous vapour, it becomes. 
incapable of reducing oxides of iron. 
The necessity which appears to me 
to exist for the agency of water in 
volcanic furnaces, 
some hundred parts of soda in Java, 
as also of sea-salt, and of several other 
ehlorides, renders it very probable that 
it is sea-water which most commonly 
penetrates into them, One objection, 
however, which I ought not to conceal, 
presents itself: namely, that it appears 
necessarily to follow from this supposi- 
tion, that the streams of lava would, 
escape through the same channels 
which-had served to convey the water,. 
since they would experience a slighter 
resistance in them than in those 
through which they are raised to the 
surface of the earth. It might also be 
expected that the elastic fluids formed 
in volcanic furnaces before the ascent 
of lava to the surface of the earth, 
would frequently boil up through 
those same channels to the surface of 
the sea. I am not aware that such a 
phenomenon has ever been observed, 
though it is very probable that the 
mophetes, so common in volcanic coun- 
tries, are- produced hy these elastic 
fluids. 
On the other hand, we may remark, 
that the long intervals between the 
eruptions and the state of repose in 
which voleanos remain for a great. 
number of years, seem to demonstrate 
that their fires become extinguished, 
or at least considerably deadened ; the 
waiter would then penetrate gradually 
* When these reflections were read 
before the Academy of Sciences, .M. 
Vauquelia observed that he had found 
carbon in the ashes ejected by. the last 
eruption of Vesuvius,—Ann, de Chim. 
tom. xxiii. p. 193, 
by 
the presence of, 
