1879.] on Recent Dctonathuj Agents. 75 



obtained. These differences in effect, obtained witli masses of different 

 thickness and weight, are due to the difference in tlieir power to resist 

 mechanical motion when struck by tlie buHet, and in the different 

 amount of resistance to penetration presented by the thin and the 

 thicker disks. 



It has been exphiined tliat nitroglycerine may be largely diluted 

 with inert solid matters without its sensitiveness to detonation being 

 reduced, while its detonation in open air becomes very much facili- 

 tated, because the mobility of the particles, and their consequent ten- 

 dency to yield to the force of a blow or detonation, is very greatly 

 diminished. But if a solid explosive agent is diluted with inert solid 

 matter the case is different ; for in such a mixture of the finely divided 

 solid with non-explosive solid particles, there must be a partial and 

 sometimes a complete separation of the particles of the explosive by 

 the interposed inert particles with which it is diluted ; hence the sensi- 

 tiveness to detonation is reduced, and its transmission by the particles 

 is retarded or altogether impeded, by a diminution of the extent of 

 contact between the substance to be detonated and the initiative deto- 

 nation, and by the barrier which the interposed non-explosive particles 

 oppose to the transmission of detonation. Thus a mixture of mercuric 

 fulminate with more than one-fifth its weight of French chalk could 

 not be detonated by means of one grain of pure fulminate enclosed 

 in a copper capsule, which was inserted into the mixture; that 

 quantity, similarly confined, sufficed to detonate undiluted fulminate 

 through a tube 8 inches long and * 5 inch in diameter. In experi- 

 ments made in this direction with finely divided gun-cotton, it was 

 found that although dilution with an inert solid, applied in the solid 

 form, reduced the sensitiveness of the material to detonation, this was 

 not the case when it was incorporated with a salt soluble in water, 

 the mixture being then compressed while in the wet state. The 

 compressed masses thus obtained were, when dried, in a condition of 

 greater rigidity than could be attained by submitting undiluted gun- 

 cotton to considerably more powerful pressure, because the crystal- 

 lisation of the soluble salt used as the diluent upon evaporation of 

 the water, cemented the particles composing the mass more rigidly 

 together. The gun-cotton was therefore presented in a form more 

 capable of resisting the mechanical action of a small charge of fulmi- 

 nate, than a more highly compressed undiluted gun-cotton, and hence 

 the reduction in sensitiveness due to the detonation of the explosive 

 compound is nearly counterbalanced by the greater rigidity imparted 

 to the mass. If a soluble oxidising agent (a nitrate or chlorate) be 

 employed as the diluting material, the predisposition to chemical 

 reaction between it and the gun-cotton (which is susceptible of some 

 additional oxidation), appears to operate in conjunction with the effect 

 of the salt in imparting rigidity to the mixture, thus rendering the 

 latter quite as sensitive to the detonating action of the minimum 

 fulminate charge as undiluted gun-cotton. Moreover, the interesting 

 fact has been conclusively established, that these compressed mixtures 



