374 



MR. J. E. PETAVEL ON THE PRESSURE OF EXPLOSIONS. 



below, a more detailed study shows that, while conserving the same configuration, the 

 actual curve may, according to circumstances, either be smooth (see Plate 21, figs. 1 

 and 2), or made up of continuous vibrations (see Plate 21, fig. 3), or, thirdly, composed 

 of a series of small but sharp steps corresponding with the successive impacts of the 

 explosion wave (see Plate 21, fig. 4). 



Effect of the Diameter of Cordite. 



The velocity of the explosion depends primordially on the diameter of the cordite, 

 but is modified to some extent by the distribution, the method of firing, and more 

 especially by the gravimetric density. Fig. 1 1 shows the rise of pressure for three 



1 000 



o 



-^ 



a 

 s 



0.01 0.02 



0.03 0.0* 0.05 0.06 

 Time in seconds. 



0.07 0.08 0.09 



Fig. 11. Showing variation of rate of explosion with size of cordite used. 



Gravimetric density 1 ; charge uniformly distributed ; cylindrical enclosure used ; A, diameter of 

 cord 0'035 inch; B, diameter of cord 0'175 inch; C, diameter of cord 0-475 inch. 



different diameters of cord (0'475 inch, 0'175 inch, 0'035 inch); the gravimetric 

 density is in every case O'lO. The largest size is used for heavy ordnance, the smallest 

 size for the army rifle. The three tests were made under the same conditions and in 

 the same enclosure. 



Fig. 12 relates to a similar experiment carried out at a higher pressure. Lastly, in 

 fig. 13, the time required for the complete combustion of cordite of various diameters 

 is plotted for three distinct gravimetric densities. 



The relation between the time occupied by the explosion and the diameter of the 

 cordite, as shown in this figure, is practically a linear one, the lines converging 



