450 



Sir AndrpAV NoUe 

 Modern Explosives. 



[Jan. 18, 



I have added to the Hst of high explosives with which I have 

 experimented the French B.N. (blanche nouvelle), which consisted of 

 nitrocellulose partly gelatinised, associated with tannin and potassium 

 and barium nitrates ; also Lyddite, which, on account of the violence 

 with which under certain circumstances it detonates, cannot be used 

 as a propellant, but is still interesting as a most useful explosive for 

 shell when ignited bj means of a suitable detonator. 



I shall return presently to the consideration of some interesting 

 points connected with the above explosives, but I desire first to give 

 you some information about the powders in use fifty years ago, and 

 the various views which were then held as regards the pressures 

 which they were capable of exerting and the potential energies which 

 they possessed. 



I do not know any physical fact upon which for many years there 

 was so wide a diiference of opinion among eminent men as the 

 pressure developed by the explosion of gunpowder. Robins, the 

 father of gunnery, put the pressure developed as low as 1000 atmo- 

 spheres (about 6*6 tons per square inch), while Hutton put it at 

 twice that value — viz. 2000 atmospheres. Rumford's celebrated 

 experiments induced that philosopher to put the pressure of gun- 

 powder as high as 101,000 atmospheres (G62 tons per square inch), 

 and, in order to account for the comparatively small velocities realised, 

 supposed that the powder in both guns and rifles burned very slowly, 

 and that thus the initial tension was never realised. It is sufficiently 

 curious that the weight of Robins's remark, that the powder he 

 employed must all be exploded before the bullet was much removed 

 from its seat, was not recognised, and he pointed out that if it were 

 not so, a much greater energy would be realised when the weight of 

 the shot was doubled, trebled, etc. ; but his experiments showed that 

 in all these cases the work done was nearly the same. Later on I 

 shall return to this point. 



In my own day similar discrepancies existed. In text-books at 

 the Royal Military Academy, Woolwich, so late as 1870, the tension 

 of fired gunpowder was put at 2200 atmospheres, while Piobert con- 



