108 



THE EXPLOSIVE WAVE. 



5. ON THE PERIOD OF VARIABLE CONDITION PRECEDING 

 DETONATION AND THE CONDITIONS OF THE ESTABLISHMENT 

 OF THE EXPLOSIVE WAVE. 



1. It is now proposed to study the conditions of the establish- 

 ment of the explosive wave, and the period of variable condition 

 preceding this establishment, a period analogous to that which 

 precedes the establishment of the sound wave. 



2. The following process has enabled precise measurements 

 to be made of the variation of the velocities during very short 



intervals of time, such 

 as *0003 of a second. 



A revolving cylinder 

 gives the following re- 

 cord: 



(1) The spark that 

 determines the initial in- 

 flammation at the mouth 

 of the tube; the trace of 

 this spark is shown at e 

 (Fig. 18). 



(2) The movement of a 

 very light piston, placed 

 at the other extremity of 

 the tube, in which it moves 

 freely. This piston is shown 

 in Fig. 17 in projection 

 upon the revolving cylinder. 

 The details of its construc- 

 tion are here shown : i.e. 

 the tube, the piston fur- 

 nished with its pencil in- 

 tended to trace its course 



upon the cylinder, and lastly the terminal cap of the piston 

 tube. 



In this way is recorded the time that elapses between the 

 two phenomena and the law of the movement of the piston 

 (Fig. 18). 



The delays are thus avoided which might result either 

 from the employment of a metallic manometer or from the 

 propagation of the phenomena to an auxiliary vessel. Each 

 number gives the average of from two to five experiments, 

 made with electrolytic gas (Ha + 0) in a caoutchouc tube 

 5 mms. in diameter. We will first study the velocities, 

 then the corresponding pressures, and lastly the limits of 

 detonation. 



17. Registration of variable 

 velocities. 



