1907.] on Fifty Years of Explosives. 451 



sidered that Runiford's first series of experiments was tolerably 

 correct, and he fixed the tension when fired in its own space at 

 23,000 atmospheres (about 150 tons per square inch). Cavalli in 

 18G7 arrived at nearly the same conclusion, making the pressure 

 24,000 atmospheres. 



I think I may say the question was set at rest by the experiments 

 made by myself, and described in the paper I wrote, assisted by my 

 friend and colleague, Sir F. Abel, in which I succeeded in determining 

 the tension of the exploded gases at various densities, and in altogether 

 retaining the gaseous products of combustion, even of charges which 

 filled entirely the chambers of the closed explosion vessels. I also 

 was able to discharge at pleasure, and measure the gaseous products 

 of combustion. The results of my experiments gave for the density 

 of unity a pressure of about 42 tons per square inch, or, say, 6500 

 atmospheres. 



My attention was very early called to the great variation in energy 

 developed by Service powders of the same make and recent manu- 

 factiu-e ; and in 1860, being then an Associate Member of the Ordnance 

 Select Committee, I pointed out that, in the experiments which I was 

 then carrying out for that body, the variation in energy developed by 

 new powders of different makes occasionally amounted to 25 per cent, 

 of the total energy developed. 



Powders on Service which were subjected to climatic influences 

 would, of course, show much greater variations, but I must add that 

 much of this variation was due to the method of proof then in force 

 — the Eprouvette Mortar, than which nothing can be conceived better 

 adapted to pass into the Service powder unsuitable for the guns of 

 that time. 



It was no doubt in a very great measure due to the unsuitable 

 nature of the powder then in use, that many of the serious failures of 

 the early rifled guns were due. With these powders, chamber 

 pressures were endured which would not be permitted in the much 

 more powerful and stronger guns now in use. 



The velocity in. those days given to spherical shot by the large 

 smooth-bore guns was generally between 1600 and 1700 f.s., but 

 when rifled guns were introduced the velocities were at first only 

 between 1200 and 1800 f.s., gradually increased to about 1400 f.s. 



The first improvement in the old powders was due to Major 

 Rodman, U.S.A., who not only appreciated the importance of the 

 size and density of the grains in diminishing excessive pressure, but 

 invented a most ingenious instrument for determining the pressure of 

 the exploded gases. With breech-loading guns this instrument gave 

 rehable results, but as the Enghsh guns at that date were muzzle- 

 loading, it was necessary to place the instrument on the outside of the 

 gun, where, owing to the run of the gas, the results were not rehable. 

 and the more convenient crusher gauge has since been almost 

 universally used. 



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