74 Professor Abel [ March 21, 



upon that required for tho development of the detonation, or if the 

 condition of the mass is such as hardly to present the requisite resist- 

 ance to mechanical motion essential for its detonation, then, results 

 intermediate between the mechanical dispersion of the mass and its 

 violent chemical dispersion or disintegration, i. e. detonation, are 

 obtained. Thus, frequent instances have been observed, especially in 

 the experiments in the transmission of detonation through tubes, in 

 whicli the initiative detonation has brought about an explosion attended 

 with little, if any, destructive etifect, portions of the mass being at the 

 same time dispersed and occasionally inflamed. Not only have such 

 results often been obtained with gun-cotton and dynamite, but even 

 mercuric fulminate, exposed to the concussion of a distant detonation 

 transmitted through a tube, has frequently been exploded in a manner 

 quite distinct from the violent detonation developed in other instances. 

 Silver fulminate, which under ordinary conditions detonates violently, 

 even when only a particle of the mass is subjected to a sufficient 

 disturbing influence, has been exploded without the usual demonstra- 

 tions of force, by the transmitted effect of a detonation of mercuric 

 fulminate. In these instances the violence of the concussion pro- 

 duced by the initiative detonation was only just bordering on that 

 required for the development of detonation, and it appears probable 

 that only some small portion of the mass operated upon was in a 

 condition or position favourable to the action of the initiative blow. 

 The remainder of the mass would then be dispersed by the gases 

 developed from the detonated portion ; in some instances the particles 

 would be inflamed at the moment of their dispersion, in others, they 

 would even escape ignition. The latter appears to be always the case 

 when gun-cotton is exploded by a blow from a hammer or falling 

 weight. However carefully the arrangements are adjusted with a 

 view to distribute such a blow uniformly over the entire mass struck, 

 the concentration of a preponderance of the force applied upon some 

 portion or portions of the entire mass, appears ahnost inevitable ; 

 hence only a small portion is actually detonated, the remainder 

 being instantaneously dispersed by the gases suddenly generated while 

 the weight is still resting upon the support. 



Some experiments made in firing at masses of compressed gun- 

 cotton, differently arranged and of different thicknesses, with a 

 Martini-Henry rifle, at short ranges, afforded interesting confirmation 

 of the correctness of the explanation given of the operation of a blow 

 upon masses of explosive material under different conditions. Disks 

 of gun-cotton of the same density and diameter, but differing in thick- 

 ness, were fired at ; they were freely suspended, and their distance 

 from the marksman was in all instances 100 yards. The thinnest 

 disks were simply perforated by the bullets, not a particle of the 

 gun-cotton being ignited. Somewhat thicker disks were inflamed by 

 the impact of the bullet, while still thicker disks, fired at under the 

 same conditions, were exploded, portions being in some instances dis- 

 persed in a burning state. No instance of detonation was, however, 



