78 Professor Abel [March 21, 



condition of the mass upon the facility with which detonation is 

 transmitted from particle to particle. In the determinations made 

 by means of the Noble chronoscope, of the velocity with which 

 detonation is transmitted along layers or trains of gun-cotton and 

 nitro-glycerine, the lecturer has included experiments with gun- 

 cotton containing different proportions of water. When the material 

 contained 15 per cent, of the liquid, some indications were obtained 

 that the rate of transmission of detonation was a little higher than 

 with dry gun-cotton; the difference was very decidedly in favour 

 of wet gun-cotton, when the latter was thoroughly saturated with 

 water. (With air-dry gun-cotton the mean rate of transmission 

 ranged in several experiments between 17,000 and 18,900 feet per 

 second ; with gun-cotton containing about 30 per cent, of water, the 

 mean rate of transmission ranged between 19,300 and 19,950 feet per 

 second.) The air in the masses of compressed gun-cotton being 

 replaced entirely by the comparatively incompressible body, water, 

 the particles of explosive are in a much more favourable condition 

 to resist displacement by the force of the detonation, and hence 

 they are more readily susceptible of sudden chemical disintegration. 

 Moreover, the variations in the rate of travel of detonation in dry 

 gun-cotton, resulting from differences in the compactness or rigidity 

 of different masses of the material, are very greatly reduced, if not 

 entirely eliminated, by saturating the disks with water and thus 

 equalising their power of resisting motion by a sudden blow. 



Another striking illustration of the influence which the physical 

 character of an explosive substance exercises over its susceptibility to 

 detonation and the degree of lacility with which its full explosive 

 force is developed, is furnished by one of the most recently devised, 

 and one of the most interesting of existing, explosive agents. 



Twelve years ago, soon after the process of producing compressed 

 and granulated gun-cotton had been elaborated by the lecturer, it 

 occurred to him to employ these forms of gun-cotton as vehicles for 

 the application of nitro-glycerine. A considerable proportion of the 

 liquid was absorbed by the porous masses of gun-cotton, and a nitro- 

 glycerine preparation analogous in character to dynamite was thus 

 obtained. The absorbent was in this case a violently explosive body 

 instead of an inert solid as in dynamite, but the quantity of nitro- 

 glycerine in a given weight of the preparation (to which the name of 

 Glyoxilin was given), was considerably less than in the Kieselguhr- 

 preparation ; hence the latter was nearly on a point of equality with 

 it, in regard to power, as an explosive agent. 



Nobel has observed that if, instead of making use of the most 

 explosive form of gun-cotton, or trinitrocellulose, a lower product of 

 nitration of cellulose (the so-called soluble or collodion gun-cotton) is 

 added to nitro-glycerine, the liquid exerts a peculiar solvent action 

 upon it, the fibrous material becoming gelatinised while the nitro- 

 glycerine becomes at the same time fixed, the two substances furnishing 

 a product having almost the characters of a compound. By macerat- 



