352 THE ADDRESSES, LECTURES, ETC., OF 



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 com- 

 pared 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 recorded by the latter were 

 always much greater than when 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 pres- 

 sure was measured at 29 tons, the wave-pressure recorded was 

 44 tons. Measurements 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 ap- 

 proaching to 50 tons on the square inch, constitutes alone a per- 

 fectly 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 erosion of the interior sur- 

 face of guns produced by the exploding charge an effect which, 

 notwithstanding the application of devices in the building up of 

 the charge specially directed to the preservation of the gun's bore, 

 have become so serious that, with the enormous charges now used 

 in our heavy guns, the erosive action on the surface of the bore 

 produced by a single round is distinctly perceptible. As there 

 appeared to be prima facie reasons why the erosive action of 

 powder upon the surface of the bore, at the high temperatures 

 developed, should be at any rate in part due to its one component 



