1892.] Pressure developed by some New Explosives. 129 



striking proofs of the regular combustion of the explosive that in all 

 such recovered cordite the diameter is so uniformly decreased that it 

 might readily be mistaken for newly-manufactured cordite of smaller 

 dimensions. 



I now make a comparison between the pressures given by cordite 

 as shown on curve B (see fig.) and those obtained from crusher 

 gauges. To facilitate this comparison I have added to the pressure 

 curves I have described a curve showing the pressures developed by 

 cordite when fired in a close vessel, and I have further added the 

 results of five rounds of cordite fired for the ^Explosives Committee 

 in the crusher-gauge gun, the pressure of each individual round at 

 each point of observation being indicated. 



The sample of cordite used in these experiments was not of the 

 same make as that employed in my own. The pressures given on the 

 axis of y denote those taken in the powder chamber, and are compar- 

 able with the crusher-gauge pressures I have given as derived from 

 my own experiments. It will be observed that the mean chamber 

 pressure indicated is two- OP three-tenths of a ton higher than that 

 I obtained; but it will be further observed that if I attempt to draw 

 a pressure curve through the mean of the crusher-gauge observation, 

 such curve would indicate pressures far higher than are necessary 

 and sufficient to develop the work impressed on the projectile. 



Again, the pressures indicated after the projectile has moved 

 1 foot are about 2 tons per square inch higher than those observed in 

 the powder chamber, and it will be further noticed that not only are 

 these observations, at all events at certain points, considerably too 

 high, but they exhibit in the forward part of the bore variations 

 quite unknown when the pressures are taken in the powder chamber. 



Thus, in the particular experiments I am discussing, the mean 

 pressure in the powder chamber being about 13'5 tons, the extreme 

 variation in the five rounds amounts only to about \\ tons per square 

 inch, while the crusher gauge placed ill the chase at a point about 

 8| feet from the seat of the shot, gave in the same number of rounds 

 an extreme variation of 3 tons per square inch, the mean pressures 

 being only about 4 tons, and it will further be noted that, while some of 

 the rounds indicated pressures below th6se deduced by the method I 

 have described, other rounds at the same point indicated pressures 

 even exceeding those which would have existed under the SRme gravi- 

 metric densities in a close vessel. It may also be noted that from the 

 crusher-gauge experiments, round 5 should have given the lowest 

 muzzle energy of the series ; as a matter of fact it gave the highest. 



My conclusion, therefore, is that, although crusher gauges placed 

 in the chase may, and doubtless do, give valuable comparative results, 

 they cannot be relied on for absolute determinations, unless confirmed 

 by observations altogether independent in their nature. 



VOL. LII. K 



