1871).] on Recent Dt^tonatlng Aycuts. 73 



siuldeu or extremely rapid transformation of a solid or li({iiid 

 explosive body into highly heated gas or vapour (whieh is the 

 effeot of a detonation), must obviously exert force which oj^erates 

 upon a body opposed to it in a manner precisely similar to the force 

 applied by opposing a body in the path of a solid mass which is set 

 into very rai)id motion. In other words, a detonation exerts a 

 mechanical eflect upon resisting bodies precisely similar to that of a 

 blow from a hammer or from a projectile j)ropelled from a gun. 

 Just as the force of a sufficiently sudden or powerful blow from a 

 hammer is transformed into heat by the resistance to the motion of 

 the hammer which the particles of an opposing body offer, and by the 

 consequent friction established between them, so the force or con- 

 cussive action exerted by the mattar set in motion when a solid or 

 liquid is converted into gas or vapour, will also be transformed into 

 heat, the development of which in an opposing body will be propor- 

 tionate to the resistance to motion which its particles offer, and to the 

 suddenness and violence of the concussion to which it is subjected. 

 The power of accomplishing the detonation of nitro-glycerine, gun- 

 cotton, or other highly explosive substances, freely exposed to the 

 air, through the agency of detonation produced in their vicinity or in 

 close contact with them, aj) pears therefore correctly ascribable to 

 the heat suddenly developed in some portion of the mass by the 

 mechanical effect, or blow exerted by that detonation, and is regulated 

 by the violence and suddenness (either singly or combined) of the 

 detonation, by the extent to which the particles composing the mass 

 of the explosive material are in a condition to oppose resistance to 

 the force, and by the degree of sensitiveness of the substance to 

 detonation, or to sudden metamorphosis, under the influence of heat 

 thus developed. 



It will now be evident why the readily yielding nature of the 

 particles of liquid nitro-glycerine tends to counteract its great sensi- 

 tiveness to detonation, and why, when the motion of the liquid parti- 

 cles is impeded by their admixture with solid matter, and when they 

 are consequently placed in a position to resist mechanical motion by 

 the force applied through the agency of detonation, its natural sensi- 

 tiveness to detonation, and the rapidity with which it can be trans- 

 mitted from particle to particle became fully developed. 



Again, the reduction of gun-cotton fibre to a fine state of division, 

 which renders the material readily convertible into very comj^act and 

 dense masses, places the particles in the condition most favourable to 

 resist mechanical motion upon the aj)plication of a blow, or of the 

 concussion resulting from a detonation ; hence, com2)ressed gun-cotton 

 is readily susceptible of detonation in proportion to the extent of 

 compression, or to its density and compactness, while loose gun-cotton 

 wool, or the lightly twisted or compressed material cannot be readily 

 detonated, because the force applied is expended in imjiarting motion to 

 the readily yielding particles of the mass. If the force a2)plied through 

 the agency of a detonator to a mass of explosive material just borders 



