380 



ME. J. E. PETAVEL ON THE PKESSUKE OF EXPLOSIONS. 



0.4 0.6 



Time in seconds. 



0.8 



1.0 



Fig. 15. Showing the effect of the shape of the enclosure on the maximum pressure developed 



by cordite of large diameter. 



Gravimetric density 1 ; charge uniformly distributed ; A and AI, in spherical enclosure ; B and BI, in 

 cylindrical enclosure; A and B, diameter of cord 0'475 inch (12 '07 millims.); AI and BI, diameter 

 of cord 0-175 inch (4 -44 millims.). 



contact with it rise much above atmospheric temperature, and the rate at which heat 

 is dissipated depends on the temperature gradient which is set up in the gaseous 

 mass. 



In previous papers* I have pointed out how the rate of transmission of heat in a 

 gas varies with the pressure. In the case of air, for instance, the law 



E x 10 6 = 403p' M + 1 -63/' 21 3 



was verified up to 1000 C. and 170 atmospheres, t At this pressure already air 

 transmits heat at the same rate as a substance having twenty times the conductivity 

 of air at atmospheric pressure. 



* 'Phil. Trans.,' A, vol. 191, pp. 501, 524, 1898; and vol. 197, pp. 229-254, 1901. 



t E is the heat abstracted from each square centimetre of surface of the hot body measured in therms 

 per second per degree temperature interval. 5 is the temperature of the hot surface measured in degrees 

 Centigrade, and p the pressure of the surrounding gas in atmospheres. 



