322 EXPLOSIVE AGENTS 



' Nitro-glycorino and analogous explosive compounds which bear some relation' to the 

 chloride of nitrogen in their power of sudden explosion, require the fulfilment of special 

 conditions for the development of their explosive force. Thus, the explosion of nitro- 

 glycerine by the simple application of heat can only bo accomplished if the source 

 of heat bo applied in such a way that chemical decomposition is established in 

 some portion of the mass, and is formed by the continual application of heat to that 

 part. 



1 The development of the violent explosive action of nitro-glycerine, freely exposed 

 to air, through the agency of a detonation, was for some time regarded as a peculiarity 

 of that substance ; it has, however, been demonstrated that gun-cotton and other ox- 

 plosive compounds and mixtures do not necessarily require confinement for the full 

 development of their explosive forco, but that this result is attainable (and very readily 

 in some instances, especially in the case of gun-cotton), by means similar to those 

 applied in the case of nitro-glyccrino. 



The manner in which a detonation operates in determining the violent explosion of 

 gun-cotton, nitro-glycerine, &c., has been made the subject of careful investigation. 

 It has been demonstrated experimentally, that the result cannot bo ascribed to the 

 direct operation of the heat developed by the chemical changes of the charge of 

 detonating material used as the exploding agent. An experimental comparison of tho 

 mechanical force exerted by different explosive compounds, and by tho samo compound 

 employed in different ways, has shown that the remarkable power possessed by the ex- 

 plosion of small quantities of certain bodies (the mercury and silver fulminates) to accom- 

 plish the detonation of gun-cotton, while comparatively large quantities of other highly 

 explosive agents are incapable of producing that result, is generally accounted for satis- 

 factorily by the difference in the amount of forco suddenly brought to bear in tho 

 different instances upon some portion of the mass operated upon. Most generally, 

 therefore, the degree of facility with which the detonation of a substance will develop 

 similar change in a neighbouring explosive substance may be regarded as proportionate 

 to the amount of force developed within the shortest period of time by that detonation, 

 the latter being, in fact, analogous in its operation to that of a blow from a hammer, 

 or of the impact of a projectile. 



' Several remarkable results of an exceptional character have, however, been obtained, 

 which indicate that the development of explosive force under the circumstances referred 

 to is not always simply ascribable to the sudden operation of mechanical force. These 

 were especially observed in the course of a comparison of the conditions essential to 

 the detonation of gun-cotton and of nitro-glycerine by means of particular explosive 

 agents (chloride of nitrogen, &c.), as well as in an examination into the effects pro- 

 duced upon each other by the detonation of these two substances. In illustration, it 

 may be instructive to give two examples. The detonation of compressed gun-cotton 

 is accomplished by the explosion of 5 grains of confined fulminate of mercury, placed 

 in contact with the mass, but it requires ten times that quantity of the violent explo- 

 sive agent, chloride of nitrogen, also confined, to produce the samo result. Again, 

 the mechanical forco exerted by the explosion of nitro-glycerine is fully equal to that 

 developed by the fulminate of mercury, yet a quantity of nitro-glycorino about seventy 

 times greater than the minimum of the fulminate required to detonate compressei I 

 gun-cotton, fails, when exploded in contact with the latter, to produce any other 

 result than tho complete mechanical disintegration of the mass. 



' Instances of the apparently simultaneous explosion of numerous distinct and oven 

 somewhat widely-separated masses of explosive substances (such as simultaneous ex- 

 plosions in several distinct buildings at powder-mills) do not unfrcquently occur, in 

 which the generation of a disruptive impulse by the first or initiative explosion, which 

 is communicated with extreme rapidity to contiguous masses of the samo nature, 

 appears much more likely to bo the operating cause than that such simultaneous 

 explosions should bo brought about by the direct action of heat and mechanical forco. 



' It need scarcely bo stated that tho detonation of a largo quantity of an explosive 

 body is accomplished by tho initiative detonation of a very small portion of tho mass ; 

 this is the case even if tho material is arranged in the form of a train of considerable 

 length, tho detonating fuze being applied at one extremity. Rows of gun-cotton disks, 

 from 3 feet to 5 feet in length, with intervals of o-,"i inch and 1 inch between the 

 individual masses, have been detonated in this way. There is, however, a limit, to the 

 distance to which a detonation will bo transmitted along a row of sjiaeed disks, the 

 limit being determined by tho particular weight of tho masses employed; it' it 1"-' 

 exceeded, those masses which are at the further extremity will bo inflamed an 

 tered, instead of being detonated. A lew preliminary experiments have, been made, 

 with the view of determining, by means of Noble's chronoscope, tho rapidity \\iih 

 which detonation progresses along a row of gun-cotton disks. This will, r.n doubt, 

 vary with the sizes of the masses. In an experiment with disks weighing 2 ounces 



