DETONATION AND SYNCHRONOUS VIBRATIONS. 81 



distance to vibrate ; detonation took place, but only for sounds 

 higher than a given note, which note represented sixty vibrations 

 per second. They then took two conjugate parabolic mirrors 

 fixed 2'5 metres apart, and they placed along the line of foci at 

 different points a few drops of nitroglycerin or grains of nitrogen 

 iodide, then they caused the detonation of a large drop of nitro- 

 glycerin on one of the foci ; they observed that the explosive 

 substances placed on the conjugate focus exploded in unison, to 

 the exclusion of similar substances placed at other points. A 

 coating of lamp-black placed on the surface of mirrors served 

 to prevent any reflection and the concentration of the calorific 

 rays. 



9. None of these tests, however, are conclusive, and several 

 of them appear absolutely contrary to the theory of synchronous 

 vibrations. In the first place it may be remarked that the fact 

 of a certain musical note being capable of determining each 

 kind of explosion has never been established properly; it is 

 only below a certain note that the effects cease to be produced, 

 whereas they take place by preference, and whatever be the 

 explosive body, in the sharpest notes. Besides, the effects cease 

 to be produced at distances incomparably less than the 

 resonance of the chords in unison, which proves that detonations 

 are functions of the intensity of mechanical action rather than 

 of the character of the vibration which determines them. De- 

 tonation also ceases to be produced when the weight of the 

 detonator is too slight, and consequently when the energy of the 

 shock is attenuated. The specific vibrating note, however, 

 which determines explosion should always remain the same. 

 For instance, cartridges of 75 per cent, dynamite cease to 

 explode when the capsule contains less than 0'2 grm. of 

 fulminate ; the explosion only being insured in any case at the 

 regulation weight of 1 grm. This confirms the existence of a 

 direct relation between the character of the detonation and the 

 intensity of the shock produced by one and the same detonator. 



If it were true that gun-cotton could explode nitroglycerin 

 by reason of the synchronism of the vibration transmitted, it is 

 difficult to understand why reciprocal action does not take 

 place ; whereas the absence of reciprocity is easily explained by 

 the difference in the structure of the two substances, which 

 plays an important part in the transformation of energy into 

 work (p. 38). 



10. This same diversity of structure and the modifications 

 which it introduces into the transmission of the phenomena of 

 shock, and the transformation of mechanical energy into calorific 

 energy, may be quoted in order to account for the facts observed 

 by Abel. 



The difference between the energy of pure fulminate and that 

 of fulminate when mixed with potassium chlorate is not any 



