1907.] 



on Fifty Years of Explosives. 

 R.L.G.. 



455 



Taking the first series in the first chamber, you will see from the 

 table, the charge being 10 lb. of R.L.G2. 



The velocity realised with the :-'>0-lb. shot was 2126 f.s., that velocity 

 falling to 691 f.s. with the o60-lb. shot, while the chamber pressure rises 

 with the successive weights from 14 tons on the square inch to 22 • 7 tons. 



To the next column, which represents the energy realised in the 

 projectile, I call your particular attention. The energy realised with 

 the 30-lb. shot is 972 ft. -tons, increasing with the 60-lb. shot to 

 1125, with the 90-lb. shot to 1178, and with the 120-lb. to 1196 ft.- 

 tons ; but here the limit of energy was reached, as with the 150-lb. 

 and the 860-lb. shot the energy is practically the same. 



Thus, although Robins was much mistaken in his estimate of 

 the maximum pressure due to fired gunpowder, liis remark that the 

 whole of the powder he employed must have been fired before the 

 shot was materially moved from its seat was fully justified, as he had 

 found that, when the weight of the shot was doubled, trebled, etc., 

 the energy realised was not very materially increased, as it should 

 have been if the combustion of the powder was so slow as some 

 authorities supposed. 



Robins's argument is unanswerable, and it is difficult to understand 

 why the great authorities, such as Rumford, Piobert, Cavalli, etc., who 

 supposed that the ignition of powder was comparatively slow, did not 

 make the simple test that Robins had proposed and had himself tried. 



Alongside the table for R.L.G..^ you see a table of results from 

 one of the slow-burning Cocoa powders, the same weight of charge 

 being used. 



Cocoa (Slow burning). 



