EXPLOSIONS TRANSMITTED BY WATER. 77 



bouring substances, although such projections often play a 

 certain part. In this respect, the real character of the effects 

 produced is shown more particularly from tests made under water. 



4. In fact, when experimenting in water, below a depth of 

 1-30 metres a charge of dynamite weighing 5 kgms. will cause 

 the explosion of a charge of 4 kgms. situated at a distance of 

 3 metres. 



The water therefore transmits the explosive shock, at any 

 rate to a certain distance, in the same way as a solid body. 

 This transmission is so violent that fishes are killed in ponds 

 within a certain radius by the explosion of a dynamite cartridge ; 

 this process is sometimes employed by fishermen, but has the 

 disadvantage of destroying all the fish. 



5. Similar trials have been made by Abel with compressed 

 gun-cotton. According to his observations the explosion of a 

 first block determines the explosion of a series of similar 

 blocks. This propagation has also been studied under water ; 

 the explosion of a torpedo charged with gun-cotton causing the 

 explosion of neighbouring torpedoes placed within a certain 

 radius. 



Sudden pressures transmitted by water have even been 

 measured by the aid of the lead crusher at different distances, 

 such as 2'50 metres, 3'50 metres, 4*50 metres and 5*50 metres. 

 They decrease with the distance, as might be expected. Besides, 

 experience proves that the relative position of the charge and the 

 crusher is immaterial, and this is in accordance with the principle 

 of equal transmission of hydraulic pressures in all directions. 



6. Explosions of fulminating substances, propagating them- 

 selves suddenly to a great number of amorces, belong to the 

 same order of explosions by influence. 



The explosion in the Eue Beranger has been previously 

 mentioned (p. 46). The experiments made on that occasion by 

 Sarrau showed that amorces, similar to those which caused this 

 catastrophe, will burn successively by simple inflammation 

 during a fire without giving rise to a general explosion, whereas 

 the explosions of some of these amorces each containing O'OIO 

 grm. of explosive matter, if produced by a sudden pressure, 

 determines, by influence, the explosions of neighbouring packets 

 even when not contiguous, and when situated at a distance of 

 0*15 metre. A general explosion, therefore, can be easily pro- 

 duced by influence under these conditions. 



2. THEORY FOUNDED ON THE EXISTENCE OF THE EXPLOSIVE 



WAVE. 



1. It follows from these facts, and particularly from experi- 

 ments made under water, that explosions by influence are not 

 due to inflammation, properly so called, but to the transmission 



