524 REPORT— 1894. 



pi'oducts of combustion themselves ; but even this error was a small one 

 compared with that which led him to adopt, as correct, his extravagant 

 estimate of the pressures developed. 



For a density of unity — or, in other words, for a charge approximately 

 filling a chamber in which it was fired — he estimated the pressure at over 

 101,000 atmospheres, or at 662 tons per square inch. 



He adopted this pressure notwithstanding the great discrepancy which 

 he found to exist between the two series of experiments which he made, 

 and he meets the objection that, were the pressure anything approaching 

 that which he gives, no gun that ever was made would have a chance of 

 standing by assuming that the combustion of powder is exceedingly slow, 

 and lasts the whole time occupied by the projectile in passing through 

 the bore. 



It is sufficiently curious that a man so eminent for his scientific attain- 

 ments as was Rumfoi-d should have fallen into so great an error, both 

 because any attempt at calculation would have shown him his mistake, 

 and because Robins, sixty years earlier, had conclusively proved that with 

 the small grain powders then used — and it must be remembered that 

 Runiford's powder was sporting of very fine grain — the whole of the 

 powder was fired before the bullet was very greatly removed from its seat. 

 Robins's argument — and it is incontrovertible — was, that were it otherwise 

 a much greater energy would be realised from the powder when the 

 weight of the projectile was doubled, trebled, quadrupled, &c. ; but his 

 experiments showed that under these circumstances the work done by the 

 powder was nearly tlie same. 



For other objects, on a much larger scale, and with appliances far 

 supeiior to those which the great man I have named had at his disposal, 

 I have had occasion to repeat Robins's experiment, and the results are 

 interesting. With a charge of 10 lb. of the powder known as R.L.G2 

 and a shot weighing 30 lb. a velocity of 2,126 f.s., representing an energy 

 of 971 "6 foot-tons, was attained. The same charge being used, but the 

 weight of the projectile being doubled, the velocity was reduced to 

 1,641 f.s., while the energy was increased to 1,125 foot-tons. With a shot 

 weighing 120 lb. the velocity was 1,209 f.s. and the energy 1,196 foot-tons. 

 With a shot of 1501b. the velocity was 1,080 f.s. and the energy 1191-5 

 foot-tons ; while with a shot of 360 lb. the velocity was reduced to 691 f.s., 

 representing a muzzle energy of 1,191 '9 foot-tons. These energies were 

 obtained with maximum chamber pressures respectively of 13'5 tons, of 

 17'25 tons, of 19 tons, of 20 tons, and of 22 tons per square inch. It will 

 be noted that the maximum energy obtained was realised with the shot of 

 1201b. weight, the energy given by a shot of 3601b. — i.e. three times 

 that weight, or twelve times the weight of the original shot — being nearly 

 exactly the same. 



Very different, however, were the results when one of the modern 

 powders, introduced with the special object of insuring slow combustion, 

 was compared with the R.L.G2 experiments which I have just quoted. 



With brown prismatic or cocoa powder an exactly similar series was 

 fired. The 30-lb. shot gave a velocity of 1,515 f.s. and an energy of 493"4 

 foot-tons ; the 60-lb. shot gave 1,291 f.s., and an energy of 693-4 foot-tons ; 

 the 120- lb. shot, 1,040 f.s., and 877-5 foot-tons; the 150-lb. shot, 948 f.s. 

 and 920-7 foot-tons ; while with the heaviest shot, the 3601b., the velocity 

 attained was 654 f.s., equivalent to an energy of 1,064-7 foot-tons. The 

 maximum chamber pressures in this series varied from 4-8 tons per square 



