452 



Sir Andreiv Noble 



[Jan. 18, 



Before the adoption of the Pebble, P2, and Prismatic powders, 

 which were due to the labours of the first Explosives Committee, the 

 chamber pressures were very high, and occasionally ran exceptionally 

 hicrh when a rapidly lighting or brisante powder was employed ; but 

 it must be remembered that these exceptional pressures did not exist 

 at the same instant throughout the chamber, but passed in waves 

 backwards and forwards from the end of the chamber to the base of 

 the projectile. 



A curious and interesting instance of this action occm'red in one 

 of two consecutive rounds fired from a 10-inch gun during experiments 

 made by the first Explosives Committee. In the first three feet of 

 the chamber and bore, five crusher gauges were placed at various 

 points, the gauge at the base of the bore being in the axis of the 

 chamber. 



The first round, which was nearly normal, gave the pressures 

 28 • 0, 29 • 8, 30 • 0, 29 • 8, and 19*8 tons per square inch. The second, 

 with which wave action was set up, gave 63*4, 41*6, 37*0, 41-9, 

 and 25*8 tons per square inch. Yet with both rounds the muzzle 

 velocity was the same, proving that the mean pressure in the bore 

 had been identical. 



But I must not detain you on these experiments, interesting as 

 they are, and I only point out to you that the labours of the first 

 Explosives Committee resulted in an increase of velocity to the same 

 projectile of over 200 f.s., viz. from over 1400 f.s. to over 1600 f.s., 

 equivalent to an increase of energy of about 33 per cent., while the 

 maximum pressure was reduced by about the same percentage, a 

 matter of very great importance in the case of breech -loading 

 guns. 



I now pass to give you the volumes of gas, and the units of heat 

 developed, also the comparative potential energy of the explosives of 

 which I have given the composition. You will observe by the table 

 that I have placed the explosives in descending order of potential 

 energy, and you will also observe how very much more powerful are 

 the modern explosives than is gunpowder, which held its own during 

 so many hundred years. 



Older Explosives. 



