CHAPTEE VI. 



EXPLOSIONS BY INFLUENCE. 



1. EXPERIMENTAL OBSERVATIONS. 



1. So far we have studied the development of explosive 

 reactions either from the point of view of their duration in 

 a homogeneous system, all the parts of which are maintained at 

 an identical temperature, or from their propagation in an equally 

 homogeneous system which is fired directly by means of a body 

 in ignition or by a violent shock. But the study of explosive 

 substances has revealed the existence of another mode of pro- 

 pagating reactions in explosives ; this propagation taking place 

 at a distance and through the medium of the air or of solid bodies 

 which of themselves do not participate in the chemical change. 



We now refer to explosions by influence, which hitherto have 

 been suspected from certain known facts in connection with the 

 simultaneous explosion of several buildings, widely separated, in 

 catastrophes at powder works. 



Attention has been especially called to this class of phenomena 

 by the study of nitroglycerin and gun-cotton. 



2. We will first cite some characteristic facts. 



A dynamite cartridge exploded by means of a priming of 

 fulminate causes the explosion of cartridges in its vicinity, not 

 only by contact and by direct shock, but even at a distance. 

 An indefinite number of cartridges in a straight line or regular 

 curve can also be exploded in this way. 



The distances at which explosion will propagate itself are, 

 comparatively speaking, considerable. Thus, for instance, with 

 cartridges contained in stiff metallic cases, and placed on firm 

 ground, the explosion caused by 100 grms. of Vonges dynamite 

 (75% of nitroglycerin, 25% of randanite, that is to say of silica 

 in a very finely divided state), communicates itself to a distance 

 of 0-3 metre, according to Captain Coville's tests. D being the 

 distance in metres and C the weight of the charge in kgms., 

 the tests of this officer have given D = 3'0 C. 



With cartridges resting on a rail he obtained D = 7*0 C. 



