94 



THE EXPLOSIVE WAVE. 



held by the electro-magnet, M, through which passes the second 



current also destined to be interrupted. 



A catch, C, consists of a knife edge (a circular milled head of 



hardened cast steel), mounted upon a spring which may be held 



firm, or tightened by the handle of a lever. 



The chronometer, on its circuit being broken, becomes 



detached and falls vertically freely; the second circuit being 



next broken, the registering apparatus falls in its turn, comes in 



contact with the free extremity of the lever and disengages the 



catch, the knife is projected forward, strikes the chronometer 



in its course, and imprints upon its 

 casing a mark, the position of which 

 enables the rapidity of the pheno- 

 menon to be calculated. The details 

 of this calculation, with corrections, 

 will be found in the "Traite sur 

 la poudre," etc., traduit et augmente 

 par Desortiaux, pp. 538 and 542. 

 1878 (Dunod). 



This method was found preferable 

 to the registration by mechanical 

 processes; the latter are subject to 

 irregularities which are of great im- 

 portance in such rapid phenomena. 



The use of too short tubes for con- 

 taining the gases was avoided, as this 

 would exaggerate errors and expose 

 the experiments to those well-known 

 disturbances which arise in the 

 vicinity of the source of the waves. 

 Eeference will be made to this point 

 as it is one of great interest, and it will be shown at 

 ne time that the variation in pressure of the gases is 



propagated with exactly the same rapidity as the ignition of 



the detonators. 



Fig. 14. Section following the 

 axis of the tube. 



again, 

 the same 



3. GENERAL CONDITIONS OF THE EXPERIMENTS. 



Our experiments had reference, 



1. To the arrangement of the tube ; 



2. To its .composition ; 



3. To its characteristics, whether open or closed ; 



4. To its length ; 



5., To the initial pressure of the gaseous compound ; 



6. To the composition of this compound which was varied 

 sometimes by introducing an inert gas, and sometimes by modi- 

 fying the nature of the combustible gas. 



Arrangement of the tube. The first experiments were made 



