OF GUN-POWDER. 9

Experiment. This air proceeds from an elastic fluid gene-rated at the decomposition of the nitre, and is essentiallydifferent from the smoke which, after a little time, fixes uponthe inside of the vessel, and produces no effect. On the con-trary, the elastic fluid proves its force and effects after aconsiderable interval of time ; whence may be inferred, thatit is a permanent fluid , and in it consists almost the wholeforce of gunpowder. It may be further observed, that thisforce is always increased by heat.

33. When the experiment is made in the first method,{26. N° 1.) in a close vessel, with a quantity of sulphur andcharcoal sufficient to decompose the nitre, if the vessel be toosmall, or a considerable time be requisite to effect the decom-position, on account of the want of sufficient proximity inthe nitrous and combustible particles, the redundancy of thesmoke inclosed in the vessel will retard the operation, thecombustible body will lose its heat, and recourse must behad to the second method of continually applying fresh fire.

34. The following experiment proves that the permanenteiaftic fluid proceeds from the saltpetre alone. Let a quan-tity of sulphur and charcoal be burned in a close vessel, thevessel be suffered to cool, and a hole be opened, no wind willbe perceived to issue : from this and other experiments, it isclear that no permanent fluid is produced by burning toge-ther these two combustible bodies. The smoke, nevertheless,is elastic when hot; but so soon as it is deprived of heat,it not only entirely loses its elasticity, but even absorbs a por-tion of the common air, and a part of the permanent elasticfluid generated from the nitre, whenever this fluid mixeswith the smoke; as will be shewn hereafter.

35. From these experiments, and others that might bemade on the fame subject, the following properties may bededuced—

1. A certain degree of heat is requisite to set fire to thecombustible bodies, and decompose the nitre.

2. The degree of heat must be increased in propor-tion to the rarefaction of the surrounding air, or to thedensity of the smoke.

3. The decomposition of the nitre being alwaysprogressive, the more intimate the mixture, and thejuster the proportion of the combustible ingredients,the sooner will it be effected.

4. In