1874.] History of Explosive Agents. 163 



fulminate was frequently exploded, through the agency of a transmitted 

 detonation, in a manner quite distinct from the violent detonation at other 

 times developed. Even the silver fulminate, which under all ordinary 

 circumstances detonates violently even when only one particle of a mass 

 is submitted to a sufficient disturbing influence, has on one or two occa- 

 sions been exploded by the transmitted effect of a detonation of mercuric 

 fulminate, without the usual destructive effect. 



This remarkable difference in the behaviour of one and the same explo- 

 sive substance, under nearly similar circumstances, has been made the 

 subject of experimental investigation, in the course of which some in- 

 teresting illustrations have been obtained of the manner in which varia- 

 tions in the resistance to mechanical motion influence the results obtained, 

 by submitting some part of a mass of explosive material to sharp blows, 

 by firing from a rifle (at different ranges) against masses of compressed 

 gun-cotton of different weight and thickness, and either freely suspended 

 in air or supported in various ways. An important exemplification of the 

 difference between explosion and detonation was obtained in the course of 

 subsequent experiments, instituted for the purpose of determining the 

 velocity with which detonation is transmitted through tubes. 



The influence of dilution, by solids and liquids, on the susceptibility of 

 explosive compounds to detonation has been made the subject of syste- 

 matic experiments, and some of the results obtained have already acquired 

 considerable importance. The dilution of a liquid and of a solid explosive 

 compound by inert solid substances produces very different results. Thus 

 the liquid (nitroglycerine) may be very largely diluted (as in the case of 

 dynamite and similar preparations) by inert solids, without any modifica- 

 tion of its sensitiveness to detonation, because this dilution does not 

 interrupt the continuity of the explosive substance. The initiative deto- 

 nator, when surrounded by such a mixture, is therefore in contact at all 

 points with some portion of the nitroglycerine, and the latter is in con- 

 tinuous connexion throughout ; hence detonation is as readily established 

 and transmitted through the mixture as though the liquid were undiluted. 

 But when a solid explosive agent is similarly diluted, there must obviously 

 be complete separation of its particles at a number of points proportionate 

 to the extent of dilution and the state of division ; the establishment of 

 detonation, or its transmission, is therefore impeded either by a diminution 

 of the extent of contact between the initiative detonator and the substance 

 to be exploded, or by the barrier which the interposed non-explosive 

 particles oppose to the transmission of the detonation, or by both causes. 



Intimate mixtures of a finely divided sensitive explosive compound 

 with an inert solid, if compressed into compact masses, become much 

 more susceptible of detonation than if they be in the loose pulverulent 

 condition ; thus compressed mixtures of finely divided gun-cotton, with 

 large proportions of inert solids, were found but little inferior in sensi- 

 tiveness to the undiluted explosive agents. If the diluent consists of a 



