208 Capt. Sir A. Noble. [June 21, 



the loss of velocity and energy due to any particular shortening of 

 the bore can be at once deduced. 



These results have been obtained by measuring the velocities every 

 round at sixteen points in the bore and at the muzzle. These data 

 enable a velocity curve to be laid down, while from this curve the 

 corresponding pressure curve can be calculated. The maximum 

 chamber pressure obtained by these means is corroborated by simul- 

 taneous observations taken with crusher gauges, and the internal 

 ballistics of various explosives have thus been completely de- 

 termined. 



Commencing with gun-cotton, with which a very large number of 

 analyses were made, with the view of determining whether there was 

 any material difference in the decomposition dependent upon the 

 pressure under which it was exploded, two descriptions were em- 

 ployed : one in the form of hank or strand, and the other in the form 

 of compressed pellets. Both natures were approximately of the same 

 composition, of Waltham Abbey manufacture, containing in a dried 

 sample about 4'4 per cent, of soluble cotton and 95'6 per cent, of 

 insoluble. As used, it contained about 2'25 per cent, of moisture. 



The following were the results of the analyses of the permanent 

 gases. They are placed in five series, viz. : 



First. Analyses showing the decomposition of the strand or hank 

 gun-cotton. Second. Analyses showing the decomposition of pellet 

 gun-cotton. 



In both these series the analyses are arranged in the order of the 

 ascending pressures under which the decomposition took place. 



Third and fourth. Examples of the decomposition of strand and 

 pellet gun-cotton when exploded by means of mercuric fulminate ; 

 and, fifth, a series showing the decomposition experienced by pellet 

 gun-cotton saturated with from 25 to 30 per cent, of water, and deto- 

 nated by means of a primer of dry gun-cotton and mercuric fulminate. 



I leave these results for discussion in the memoir which Sir F. Abel 

 and I hope before long to submit, and will only remark that, in 

 Tables I and II, the same peculiarity we have before remarked upon 

 in reference to gunpowder, is again exhibited ; I mean the marked 

 manner in which the carbonic anhydride increases with the pressure. ' 

 It will be noted that in Table I the volumes of carbonic anhydride 

 and carbonic oxide are nearly exactly reversed ; again, considering 

 that the composition of the pellet and strand gun-cotton is practically 

 the same, the distinct difference between the proportions of these pro- 

 ducts in the two series is sufficiently remarkable. It not improbably 

 is connected with the rapidity of combustion of the two samples. 

 Another striking peculiarity is the manner in which the C0 2 is in- 

 creased (as exhibited in Table V) when saturated pellet cotton is ' 

 detonated. 



