70 Professor Ahel [March 21, 



much greater force, would be needed to effect the detonation of the 

 material operated upon. This view has received considerable support 

 from results since obtained by other experimenters, especially by 

 MM. Champion and Pellet ; but the subject is one which still needs 

 further experimental elucidation. 



The physical character of explosive substances, as also the 

 mechanical condition of a mass of the particular explosive substance 

 operated on, are of great influence in determining its behaviour 

 when submitted to the action of an initiative detonation. The liquid 

 nitro-glycerine is far more sensitive to detonation than gun-cotton ; 

 one grain of mercuric fulminate, confined in a metal case, suffices to 

 detonate nitro-glycerine when surrounded by it : but, in order to attain 

 this result with any degree of certainty, it is necessary so to confine 

 the nitro-glycerine as to prevent its yielding to the blow developed by 

 the initiative detonation, and thus to some extent escaping from the 

 operation of the sudden concussion to which the particles contiguous 

 to the fulminate charge are submitted. 



If nitro-glycerine be mixed with solid substances in a fine state of 

 division, plastic mixtures may be obtained, and the liquid may thus 

 be presented in something 1 ke a solid form to the detonating agent ; 

 if the particles of absorbent material be moreover of porous nature, as 

 is the case with the infusorial earth called Kieselguhr used in the 

 production of dynamite, a solid nitroglycerine preparation may be 

 obtained which contains a very large proportion of the liquid (75 per 

 cent, by weight). In this condition nitro-glycerine may be detonated 

 without any difficulty when freely exposed to air ; and although it is 

 diluted with a considerable proportion of absolutely inert material, 

 its sensitiveness to detonation is not in the least diminished. Each 

 particle of the diluent is enveloped in the liquid, so that no por- 

 tion of the latter becomes isolated from the remainder by the admix- 

 ture of inert solid matter ; hence, when the initiative detonator is 

 surrounded by such a mass, it is in contact at all points with some 

 portion of the nitro-glycerine, and the latter is in continuous con- 

 nection throughout, though no longer in a mobile condition ; 

 detonation is consequently as readily established and transmitted 

 through the mass as though it consisted entirely of nitro-glycerine. 

 Indeed, while the liquid in its undiluted state, if freely exposed to air 

 in a long layer, transmits detonation with difficulty, and very slowly 

 as compared with compressed gun-cotton (the observed rate of pro- 

 gression being, in several experiments, below 6000 feet per second), 

 detonation is transmitted with ease and certainty through very long 

 trains of a solid preparation of nitro-glycerine, such as dynamite, 

 and the rate of transmission is decidedly more rapid than it is with 

 compressed gun-cotton, a result which is in harmony with the greater 

 sensitiveness to detonation and the greater violence of action of nitro- 

 glycerine. 



It has already been stated that gun-cotton may be detonated if a 

 confined charge of not less than 2 grains of mercuric fulminate be 



