440 Mr, F. A, Abel on the Causes, Effects, [IVIarch 21. 



percussion, or concussion ; and, in a few instances, by establishing 

 chemical action in a small portion of the mixture, with the aid of some 

 other compound. These explosive mixtures vary greatly in the ease 

 with which chemical action is established in them, and in the rapidity 

 and violence of their transformation ; their properties are naturally 

 regulated by the chemical and physical characters of their consti- 

 tuents, and by the degree of intimacy of their mixture. 



The variation in their explosive properties, and the great extent 

 to which the characters of any particular mixture may be modified, 

 are very important elements in their application to practical pur- 

 poses ; while the comparatively instantaneous nature of the de- 

 composition of explosive compounds, and the facility with which 

 it is brought about, present very great, and in many cases in- 

 superable, obstacles to their employment as explosive agents. By 

 the comparatively gradual decomposition of an explosive mixture, 

 such as gunpowder (when employed as a charge in a gun), the force 

 exerted, by the gases generated in the confined space, discovers, 

 before it attains its maximum, that portion of the chamber en- 

 closing the powder {i. e. the projectile) which is separated from 

 the remainder. By the motion which it immediately imparts to this, 

 the smaller mass, the strain upon the larger mass, forming all but one 

 side of the chamber {i. e. the breech of the gun), is at once relieved, 

 while the force continues, to the close of its development, to act in the 

 direction of the mass which has once yielded to its influence, and thus 

 propels the projectile. The explosion of a charge of a fulminate, on 

 the other hand, in the chamber of a gun, is so instantaneous that the 

 maximum of force is at once developed, and the strain thus exerted 

 within the chamber, at the same time that it overcomes the inertia of 

 the projectile (or the movable side of the chamber), will also over- 

 whelm the cohesive force which maintains the mass of the chamber 

 entire, and the breech of the gun will therefore be shattered. 

 Enclosed in a shell, a charge of a fulminate will produce a much 

 greater shattering effect than gunpowder upon the metal enveloped, 

 reducing it to a much larger number of fragments ; but the pieces of 

 the shell, produced by employing gunpowder as the bursting agent, will 

 be propelled with much greater violence, because there is still a 

 development of force after the rupture of the shell, while, with the 

 fulminate, the entire force is at once expended upon the bursting of the 

 shell. 



The very great extent to which the rapidity of explosion of gun- 

 powder may be modified to suit different applications, is one of the 

 most important properties possessed by this material. A very rapidly 

 burning powder is necessary in many instances; for example, in 

 shrapnel shells, in which the charge of powder is required to break 

 open the shell without interfering, by any great dispersive effect, with 

 the flight of the enclosed bullets or fragments of metal. In mortars, 

 and short guns also, a quickly burning powder is required, as they 

 afford a comparatively limited space for the combustion of the charge. 



