1879. 1 on Recent Defonating Agents. 85 



ciii'tridgcs will be frozen harder or more tlioroughly than the interior. 

 It may thus arise that portions of only partially frozen or still 

 unfrozen dynamite may be more or less completely enclosed in hard 

 crusts, or strong envelopes, of perfectly frozen and comparatively 

 very cold dyamite. On exjiosure of such cartridges to a fierce heat 

 very rapidly applied, as would result from the burning of a con- 

 siderable quantity of the material, some portion of one or other of 

 the cartridges would be likely to be much more readily raised to the 

 igniting or exploding point than the remaining more perfectly frozen 

 part in which it is partly or completely imbedded. If the ignition 

 of this portion be brought about (which it will be with a rapidity 

 proportionate to the intensity of heat to which the cartridge is 

 exposed), the envelope of hard frozen dynamite by which it is still 

 more or less completely surrounded and strongly confined, will 

 operate like the metal envelope of a detonator, in developing the 

 initial pressure essential for the sudden raising of the more readily 

 inflammable portion of the dynamite to the temperature necessary for 

 the sudden transformation of the nitro-glycerine into gas, and will 

 thus bring about the detonation of a portion of the cartridge, which 

 will act as the initiative detonator to the remainder of the dynamite. 

 On igniting separately, at one of their extremities, some dynamite 

 cartridges which had been buried in snow for a considerable period, 

 the lecturer has observed that, as the frozen material gradually 

 burned away, very slight but sharp explosions (like the snapping of a 

 small percussion cap on a gun nipple) occurred from time to time, 

 portions of the frozen dynamite being scattered with some violence. 

 He did not succeed in obtaining actual detonation by thus burning 

 frozen cartridges surrounded by others in a similar condition, but he 

 has been informed by Mr. McRoberts, of the Ardeer Dynamite Works, 

 that he has more than once detonated a small heap of hard-frozen 

 cartridges weighing altogether one pound, by igniting one cartridge 

 which was surrounded by the remainder. These facts appear to 

 substantiate the correctness of the foregoing explanation. They 

 point to the danger of assuming that, because dynamite in the frozen 

 state is less sensitive to the effects of a blow or initiative detonation, 

 than the thawed material, it may therefore be submitted without 

 special care to the action of heat, for the purpose of thawing it. 

 Instances of the detonation, with disastrous results, of even single 

 cartridges of frozen dynamite, through the incautious ajiplication of 

 considerable heat (as for example by placing them in an oven, or 

 close to a fire), have been, and are still, of not unfrequent occurrence, 

 even though Mr. Nobel has insisted upon the application of heat 

 through the agency only of warm water, as the sole reliable method 

 of safely thawing dynamite cartridges. 



While the sensitiveness to detonation of air-dry gun-cotton 

 remains unaffected by great reduction in temperature of the mass, and 

 while in this respect it presents advantages over nitro-glycerine 



