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liberates a still larger quantity of the inflammable air. or robbing the me¬ 
tallic oxyds of their oxygen is converted into the oxygenated muriatic acid, 
which has the property to form with potash, a salt, which rapidly kindles hot 
inflammable matter, and produces the purest vital air known. When these 
two airs are in great abundance in the hollow caverns of the earth bordering 
on the sea, and this aerial gunpowder * gets kindled, which may arise either 
In the West Indies, on the island of Guadaloupe, is a hill called La Soufriere, or the Mountain of 
Sulphur, which rises to a great height; the top of it is bare, nothing growing upon it but fern, and 
some sorry shrubs laden with moss; but it affords a fine view of Dominica, Mariagalante, Martinico, 
Montserrat, Nevis, and the other neighbouring islands. Upon the highest part is a rugged platform, 
covered with burnt stones of all sizes; and from several clefts and chinks issue smoke. On the east 
side are two mouths, which open into a pit of sulphur, one of which is an oval hole of about an hun¬ 
dred feet in its greatest diameter, out of which also frequently arise thick clouds of black smoke, 
accompanied with sparks of fire. The negroes who sell brimstone fetch it from this mountain. About 
two hundred paces below the lowest of these mouths are three pools of very hot water, four or five 
paces from one another: the water of the largest is very dark coloured, and smells like that in a smith’s 
forge: the second is whitish, and has the taste of allum: the third is blue, and has a vitriolic taste. 
The Marquis Ippolito, in his letter to Sir William Hamilton, which he published, relates, that im¬ 
mediately after the late earthquake, the waters of a well in Maida (one of the towns overthrown) of 
which the inhabitants used to drink, became of so strong a sulphureous taste, that it was impossible to 
smell to it. 
* Hydrogenous gas , or inflammable air , may be extracted from all bodies in which it is a constituent 
part; but the purest is that afforded by the decomposition of w^ater. For this purpose the sulphuric 
acid diluted with water, is poured upon iron, or zinc; and the water, which serves as a vehicle for the 
acid, is decomposed on the metal; its oxygen combines with it, while the hydrogenous gas escapes. 
This explanation, however contrary to the ancient notion, is not the less a demonstrated truth; in 
fact, the metal exists in the state of an oxyd in its solution by the sulphuric acid, as may be proved by 
precipitating it with pure vegetable alkali: on the other hand, the acid itself is not at all decomposed; 
so that the oxygenous gas cannot have been afforded to the iron but by the water. Water may be 
decomposed likewise still more directly by throwing it upon iron strongly heated; and hydrogenous 
gas may be obtained by causing water to pass through a tube of iron ignited to whiteness. 
* Hook, as we saw, was the first to conjecture, that volcanic explosions arose from certain combi¬ 
nations resembling gunpowder, and that this might arise from an aerial product. His conjecture has 
been since amply verified, and an aerial gunpowder has been employed in lieu of solid forms, liberating 
glasses. 
Tig. 18 th, represents a small pistol, necessary to shew the force of exploding inflammable air. 
Since these instruments were introduced, their form has been very much diversified; some having been 
made of brass, and so large as to drive a leaden bullet; others have been made of tin, &c.; but that 
shewn by this figure is of glass, and so simple, that it may be easily constructed, even by persons of 
no great genius; and gives a sufficient idea of the power of exploding inflammable air, by driving a 
cork to a considerable distance. 
ABD is a strong glass tube five inches long, and about half an inch in diameter. Into the inside 
of this tube, and towards one extremity of it, a small slip of tinfoil CB is pasted, so as to be about two 
inches within the tube, and be turned on the outside of it at B. Into this same extremity BD the 
small wire G H, knobbed at its extremity H, must be cemented very fast. The best method is to 
cement the wire into a small glass tube F, and then to wrap some cotton on thread round this small 
tube, and to cement it into the extremity BD of the pistol. Th? end G of the wire should be bent 
towards the slip ot tinfoil C, so as to come within about one tenth of an inch of it. Now when this 
