136 



Capt. Noble and Mr. F. A. Abel. 



[May 29, 



Nature of powder. 



Units of heat 

 per gramme 

 exploded. 



Cub. centims. of 

 gas per gramme 

 exploded . 



Spanish pellet powder 

 Curtis and Harvey's No. 6, 



W.A.F.Gr 



W.A.R.L.a 



W.A. Pebble 



Mining 



767-3 

 764 '4 

 738-3 

 725-7 

 721 -4 

 516-8 



234-2 

 241 -0 

 263-1 

 274-2 

 278-3 

 360-3 



The results given in this table are very striking. Taking the two 

 natures of powder which commence and close the list, the heat gene- 

 rated by the Spanish powder is about 50 per cent, higher than that 

 generated by the mining powder, while the quantity of permanent 

 gases evolved by the latter is about 50 per cent, greater than that given 

 off by the former. 



Thus it appears that the great inferiority of heat developed by the 

 mining powder, as compared with the Spanish powder, is compensated, 

 or at least approximately so, by the great superiority in volume of 

 permanent gases produced. A similar relation is observed in respect 

 to the other powders, and it would indeed appear that the pressures at 

 any given density and the capacity for performing work of the various 

 powders are not very materially different. 



This fact has been entirely verified for the whole of the Waltham 

 Abbey powders, and in a less degree for the three other powders also. 



The peculiarities shown by the mining powder are so interesting 

 that it appeared important to determine its tension when fired under 

 a high gravimetric density. 11,560 grs. (749 grms.) of this powder 

 have, therefore, been fired under a gravimetric density of unity. 

 The pressure developed by two very accordant observations was, 

 when corrected, 44 tons on the square inch (6,706 atmospheres). The 

 pressure obtained under similar circumstances from Waltham Abbey 

 powder was 43 tons on the square inch (6,554 atmospheres). 



It will afterwards be seen that the capacity for performing work of 

 the various descriptions of powder was also found to be not very 

 different, a similarity of result the more remarkable when it is remem^ 

 bered that with, at all events, three of the powders there were striking- 

 differences both in their composition and in the decomposition they 

 experience, and when in consequence material variations both in pres- 

 sures at different densities and in potential energy might have been 

 expected. 



With respect to the great difference in heat evolved by the Spanish 

 and mining powders, it appears difficult to resist the conclusion that 

 the small number of units of heat evolved by the latter is in great 

 measure due to the quantity of heat absorbed in placing the very much 



