80 EXPLOSIONS BY INFLUENCE. 



transformation incessantly reproduced from chemical actions 

 into calorific and mechanical actions, which transmit the shock 

 to the supports and to contiguous bodies ; and the other purely 

 physical and mechanical, which also transmits sudden pressures 

 around the centre of vibration to neighbouring bodies and by a 

 peculiar circumstance to a fresh mass of explosive matter. 



The explosive wave, once produced, propagates itself without 

 diminishing in force, because the chemical reactions which 

 develop it regenerate its energy proportionately along the whole 

 course ; whereas the mechanical wave is constantly losing its 

 intensity in proportion as its energy, which is determined ^only 

 by the original impulsion, is distributed into a more considerable 

 mass of matter. 



7. A different theory than this was at first proposed by 

 Abel, namely, the theory of synchronous vibrations, of which it 

 will be well to speak now. According to this authority the 

 determining cause of the detonation of an explosive body resides 

 in the synchronism between the vibrations produced by the 

 body which provokes the detonation and those which would be 

 produced by the first body when detonating, precisely as a 

 violin-string resounds at a distance in unison with another 

 chord, set in vibration. In support of this, Abel cited the 

 following facts. In the first place, detonators appear to be 

 special for each kind of explosive substance. For instance, 

 nitrogen iodide, which is very susceptible to shock and friction, 

 does not appear to be able to cause the detonation of compressed 

 gun-cotton. Nitrogen chloride, so easily explosive of itself, only 

 produces detonation when a weight ten times that of the neces- 

 sary fulminate is employed. In the same way nitroglycerin does 

 not cause the detonation of gun-cotton in sheets on which the 

 envelope containing it is placed. In this way 23'3 grms. of 

 nitroglycerin have been made to detonate without success. On 

 the other hand, the inverse influence is proved, 775 grms. of 

 compressed gun-cotton having detonated nitroglycerin enclosed 

 in an envelope of thin foil at a distance of 0'02 metre. A 

 priming formed of a mixture of potassium ferrocyanide and 

 potassium chlorate will not cause gun-cotton to detonate 

 (according to Brown). 



Finally, according to Trauzl, a much greater weight of a 

 priming made of a mixture of mercury fulminate and potassium 

 chlorate. should be taken than if it were formed of fulminate 

 alone. Nevertheless the heat liberated by unit weight is one- 

 fifth greater with the former mixture. 



8. Champion and Pellet have adduced the following experi- 

 ments in support of this ingenious hypothesis : they fixed on 

 the string of a contra-bass particles of nitrogen iodide, a 

 substance which detonates by the slightest friction. They 

 then caused the strings of a similar instrument situated at a 



