SIR WILLIAM SIEMENS, F.R.S. 351 



When the British Association met at Southampton on a former 

 occasion, Schonbein announced to the world his discovery of gun- 

 o it ton. This discovery has led the way to many valuable researches 

 on explosives generally, in which Mr. Abel has taken a leading 

 part. Recent investigations by him, in connection with Captain 

 Nohle, upon the explosive action of gun-cotton and gunpowder 

 confined in a strong chamber (which have not yet been published), 

 deserve particular attention. They show that while by the method 

 of investigation pursued about twenty years ago by Karolye (of 

 exploding gunpowder in very small charges in shells confined 

 within a large shell partially exhausted of air), the composition 

 of the gaseous products was found to be complicated and liable to 

 variation, the chemical metamorphosis which gun-cotton sustains, 

 when exploded under conditions such as obtain in its practical 

 application, is simple and very uniform. Among other interesting 

 points noticed in this direction was the fact that, as in the case of 

 gunpowder, the proportion of carbonic acid increases, while that 

 of carbonic oxide diminishes with the density of the charge. The 

 explosion of gun-cotton, whether in the form of wool or loosely 

 spun thread, or in the packed compressed form devised by Abel, 

 furnished practically the same results if fired under pressure, that 

 is, under strong confinement the conditions being favourable to 

 the full development of its explosive force ; but some marked 

 differences in the composition of the products of metamorphosis 

 were observed when gun-cotton was fired by detonation. 



With regard to the tension exerted by the products of ex- 

 plosion, some interesting points were observed, which introduce 

 very considerable difficulties into the investigation of the action 

 of fired gun-cotton. Thus whereas no marked differences are 

 observed in the tension developed by small charges and by 

 very much larger charges of gunpowder having the same 

 density (i.e. occupying the same volume relatively to the entire 

 space in which they are exploded), the reverse is the case with 

 respect to gun-cotton. Under similar conditions in regard 

 to density of charge, 100 grammes of gun-cotton gave a 

 measured tension of about 20 tons on the square inch, 1500 

 grammes gave a tension of about 29 tons (in several very 

 concordant observations), while a charge of 2 - 5 kilos gave a 

 pressure of about 45 tons, this being the maximum measured 



