SONOKOUS VIBRATIONS. 



83 



influence are explained more simply, as has been said above, by 

 the direct effect of the shock propagated by gases at short 

 distances, beyond which they do not propagate themselves in 

 any way. As to nitrogen iodide, which is the subject of the 



principal observations relative to explosions by resonance, it is 

 a powder so sensitive to friction that it may be asked whether 

 its detonation does not take place by shock and by the friction 

 of the supports, the real seat of resonance in unison. 



G2 



