64 Professor Abel [March 21, 



in its action than the pure fulminate, must be used in comparatively 

 large quantities to accomplish the detonation of gun-cotton. 



The essential difference between an explosion and what we now 

 distinguish as a detonation lies in the comparative suddenness of the 

 transformation of the solid or liquid explosive substance into gas and 

 vapour. 



The gradual nature of the explosion of gunpowder is illustrated, 

 in its extreme, by burning a train of powder in open air ; the rapidity 

 and consequent violence of the explosion is increased in proportion to 

 the degree of confinement of the exi^loding charge, or to the resistance 

 opposed to the escape or expansion of the gases generated upon the 

 first ignition of the confined substance. In proj^ortion as the pressure 

 is increased under which the progressive transformation of the ex- 

 plosive takes place, the rapidity with which its particles are succes- 

 sively subjected to the action of heat is increased. 



In the case of a very much more sensitive and rapidly explosive 

 substance than gunpowder, such as mercuric fulminate, the increase 

 in the rapidity of its transformation, by strong confinement, is so 

 great that the explosion assumes the character of a detonation in 

 regard to suddenness and consequent destructive effect. A still more 

 sensitive and rapidly explosive material (such as the silver fulminate 

 and iodide of nitrogen) produces when exploded in open air effects 

 akin to those of detonation ; yet even with these bodies, confinement 

 operates in increasing the rapidity of the explosive to suddenness, 

 and consequently in developing a more purely detonative action. 

 Thus, the violence of explosion of silver fulminate is decidedly in- 

 creased by confining the substance in a stout metal case, and the 

 enclosure of iodide of nitrogen in a shell of plaster of paris has a 

 similar effect. With chloride of nitrogen, the suddenness of detona- 

 tion, and consequently the violence of action, was found to be very 

 greatly increased even by confining the liquid beneath a thin layer 

 of water. 



Detonation, developed in some portion of a mass, is transmitted 

 with a velocity approaching instantaneousness throughout any quan- 

 tity, and even if the material is laid out in the open air in long trains 

 composed of small masses. The velocity with which detonation 

 travels along trains thirty or forty feet in length, composed of distinct 

 masses of gun-cotton and of dynamite, has been determined by means 

 of Noble's chronoscope, and was found to range from 17,000 to 24,000 

 feet per second. Even when trains of these explosive agents were laid 

 out with intervening spaces of half an inch between the individual 

 masses composing the trains, detonation was still transmitted along 

 the separated masses with great though diminished velocity. 



The suddenness with which detonation takes place has been 

 applied as a very simple means of breaking up shells into small 

 fragments and scattering these with considerable violence, with em- 

 ployment of very small charges of explosive agent. Thus by filling 

 a IC-pr. common shell completely with water and inserting a charge 



