248 Mr. F. J. Bramwell [June 13, 



1487, showing that the mean pressure must have been only 76 per cent, 

 of that which would have prevailed if no air space had been left ; 

 and further, so far from the maximum pressure having been even 

 locally increased, at the bottom of the bore of the gun it was but 

 11*7 tons, while at the base of the projectile it could not have 

 amounted to 10 tons on the square inch, as none of these three gauges 

 had moved. 



In the next experiment the air space was as much as 4 feet; the 

 muzzle velocity was only 1067 feet, instead of the 1487, showing 

 that the average pressure was only 68^ per cent, of that which would 

 have prevailed without an air space. 



In this experiment the crusher gauge in the bottom of the bore 

 and that in the centre of the base of the projectile had been previously 

 subjected to 10 tons j)ressure, while the gauges at the top and 

 bottom were left in their natural condition. The pressures recorded 

 were, at the bottom of the bore 10*15 tons ; at the top of the projectile 

 7 • 6 tons ; at the bottom 6 tons, and at the centre something below 

 10 tons, as the gauge was not affected. 



These two experiments having totally failed to set up a local 

 pressure, the next experiment was made not with pebble powder but 

 with the rifle large grain. The air space was again 4 feet ; on this 

 occasion the pressure at the bottom of the bore was 16 '7 tons upon 

 the square inch ; on the top gauge in the projectile was 25*5 tons ; in 

 the centre of the projectile was 35 • 3 tons ; and at the bottom was 23*3 

 tons ; while with this powder had the gun been fired without an air 

 space the pressures would have been from 27 to 30 tons. In these 

 experiments no wad was used, and it was determined to make others 

 with a disc wad. In the first instance 85 lbs. of pebble powder 

 being employed, and a 6 -feet air space being left, the wad being 

 close to the projectile, the muzzle velocity was 849 feet, the 

 pressure at the bottom of the bore under 10 tons, in the base of the 

 shot at top under 8 tons, in the centre 5 * 6 tons, and at the bottom 

 under 8 tons. The last experiment consisted in leaving a 2-feet air 

 space between the cartridge and projectile, and a 4-feet air space be- 

 tween the projectile and the canted disc wad, while the muzzle velocity 

 was 1208 feet as compared with the 1240 feet of the previous experi- 

 ment with the 2-feet space ; the pressure at the bottom of the bore was 

 11*1 tons as compared with 11*7 on the former occasion; while the 

 pressure at the top of the base of the projectile was 7 * 9 tons, at its 

 centre was 9 * 2 tons, and at its bottom 8 * 4 tons on the square inch. 

 During the previous experiment it will be remembered that the gauges 

 having been adjusted for 10 tons afforded no other information than 

 that that pressure had not been reached. 



I think these results sufficiently show that no harm would ensue 

 from pebble powder, even if air spaces had existed, but there was abun- 

 dant evidence to prove that in the ' Thunderer ' gun no air space did 

 exist ; but time compels me to refer you to the report and minutes for 

 this proof. But once more, let me remind you that an explosion of 



