102 Dr. J. //. Gladstone [May 4, 



to be always N II I^. The chloride is a still more dangerous sub- 

 stance, since it explodes with the greatest facility under water. It 

 is an oily liquid, discovered simultaneously in 1811, by M. Dulong, 

 in France, and by a young English chemist, Mr. Burton, of Ton- 

 bridge. Dr. Gladstone's analyses gave as its composition Ng H Q\. 

 The qualities requisite to render an explosive practically useful 

 were then considered. This depends, of course, upon the purpose 

 to which the explosive is to be applied. If it be merely for the 

 production of an instantaneous flame in order to ignite some other 

 body, those compounds which are exploded by percussion liave a 

 great advantage. —Percussion caps of various kinds were exhibited 

 — those intended for muskets being filled with a mixture of equal 

 parts of fulminating mercury and chlorate of potash, fixed by a 

 varnish ; those made use of for cannon, being charged with two 

 parts of chlorate of potash, two of native sulphuret of antimony, 

 and one of powdered glass, which last appears to be practically a 

 beneficial ingredient, although it takes no part in the chemical 

 action. Caps made of fulminating mercury and collodion, bronzed 

 over, were also shown. — Explosives, however, are generally intended 

 for the projection of missiles, or for blasting. For either of these 

 purposes propulsive force is the grand requisite. Now most of the 

 compounds previously described explode too rapidly, and produce a 

 very powerful local effect. If employed in fire-arms they would 

 tear or strain the gun, and not propel the ball any great distance. 

 Gunpowder, if tightly compressed, as in a fuse, or a port-fire, burns 

 comparatively slowly ; the necessary rapidity of explosion is given 

 to it by granulation ; and this can be modified according as the 

 different purposes for which it is manufactured require. Supposing 

 an explosive to have the necessary propulsive power, a very important 

 quality is safety- — safety in the process of manufacture, and in its 

 subsequent keeping and handling. This practically excludes the 

 use of all those compounds which are exploded by a blow. Gun- 

 powder requires a temperature of 600° Fah. to ignite it ; and this 

 gives it a great advantage over gun-cotton, which is fired by a heat 

 not much exceeding that of boiling water. — The comparative diffi- 

 culty of exploding gunpowder was exhibited by setting fire to some 

 ether round about a portion of it, which remained unaffected in the 

 middle of the large flame ; and by igniting a piece of gun-cotton 

 without firing the little heap of powder on which it rested. Gun- 

 powder may even be sprinkled on the top of gun-cotton, and the 

 latter may be exploded, and cause the scattering of the black grains 

 unaltered. — It is a desideratum that the explosive should not be 

 injured by wetting. In this respect gunpowder fails, while gun- 

 cotton, and several of the substances previously mentioned, suffer 

 no injury by being soaked in water and dried again. Good gun- 

 powder, however, is not materially affected by the ordinary damp 

 of tlie atmosphere. Nitrate of soda, though it contains a much 

 larger amount by weight of gas-forming constituents, cannot be 



