28 EEPOET— 1882. 



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 jji'oducts of explosion, some interesting points 

 were observed, wliich 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 I'everse is the case with respect to gun-cotton. Under 

 similar conditions in regard to density of charge, 100 gi'ammes of gun- 

 cotton gave a measured tension of about 20 tons on the square inch, 

 1,500 grammes gave a tension of about 29 tons (in several very con- 

 cordant observations), while a charge of 2'5 kilos gave a pressure of 

 about 4.5 tons, this being the maximum measured tension obtained with 

 a charge of gunpowder of five times the density of the above. 



The extreme violence of the explosion of gun-cotton as compared with 

 gunpowder when fired in a closed space was a feature attended with 

 formidable difficulties. In whatever way the charge was arranged in the 

 firing cylinder, if it had free access to the inclosed crusher gauge, the 

 pressures recoi'ded by the latter were always much greater than Avhen 

 means were taken to prevent the wave of matter suddenly set in motion 

 from acting directly upon the gauge. The abnormal or wave-pressures 

 recorded at the same time that the general tension in the cylinder was 

 measured amounted in the experiment to 42'3 tons, when the general 

 tension was recorded at 20 tons ; and in another, when the pressure was 

 measured at 29 tons, the wave-pressure recorded was 44 tons. Measure- 

 ments of the temperature of explosion of gun-cotton showed it to be about 

 double that of the explosion of gunpowder. One of the effects observed 

 to be produced by this sudden enormous development of heat was the 

 covering of the inner surfaces of the steel explosion-vessel with a network 

 of cracks, small portions of the surface being sometimes actually fractured. 

 The explosion of charges of gun-cotton up to 2'5 kilos in perfectly closed 

 chambers, with development of pressures approaching to 50 tons on the 

 square inch, constitutes alone a perfectly novel feat in investigations of 

 this class. 



Messrs. Noble and Abel are also continuing their researches upon fired 

 gunpowder, being at present occupied with an inquiry into the influence 

 exerted upon the chemical metamorphosis and ballistic effects of fired 

 gunpowder by variation in its composition, their attention being directed 

 especially to the discovery of the cause of the more or less considerable 

 prosion of the interior surface of guns pi'oduced by the exploding charge — : 



