86 Professor Abel [March 21, 



preparations, wet gun-cotton becomes very decidedly more susceptible 

 to detonation when frozen. Thus the detonation of gun-cotton con- 

 taining an addition of from 10 to 12 per cent, of water is somewhat 

 uncertain with the employment of 100 grains of strongly confined 

 fulminate, and 200 grains are required for the detonation of the 

 substance when containing 15 to 17 per cent, of water ; but the latter 

 in a frozen state can be detonated by means of 30 grains of fulmiuate, 

 and 15 grains are just upon the margin of the amount requisite for 

 detonating, with certainty, frozen gun-cotton containing 10 to 12 

 per cent, of water. The deadening effect of solid water upon the 

 sensitiveness of gun-cotton to detonation is, in fact, intermediate 

 between those of a liquid and of inert solid substances. 



The effects produced and products formed by the exjDlosion of 

 gun-cotton in perfectly closed spaces, both in the loose, and the com- 

 pressed form, and by its detonation in the dry and the wet state, have 

 been made the subject of study by Captain Noble and Mr. Abel, the 

 method of research pursued being the same as that followed in their 

 published researches on fired gunpowder; results of considerable 

 interest in regard to the heat of explosion, the pressures developed, 

 and the products of explosion of dry and wet gun-cotton have been 

 obtained, which are about to be communicated to the Royal Society. 



It may briefly be stated that the temperature of explosion of gun- 

 cotton is more than double that of gunpowder (being about 4400° C.) ; 

 that the tension of the j^i'f^cl^^cts of explosion, assuming the material 

 to fill entirely the space in which it is fired, is considerably more than 

 double that of the powder-products under the same conditions ; that 

 the products obtained by the explosion of dry gun-cotton are com- 

 paratively simple and very uniform under different conditions as 

 regards pressure ; that the products of detonation of dry gun-cotton 

 do not differ materially from those of its explosion in a confined space, 

 but that those furnished by the detonation of wet gun-cotton present 

 some interesting points of difference. Messrs. Noble and Abel are 

 extending their investigations to the nitro-glycerine preparations. 



The great advance which has been made within the last twelve 

 years in our knowledge of the conditions which determine the cha- 

 racter of the metamorphosis that explosive substances undergo, and 

 which develop or control the violence of their action, finds its parallel 

 in the progress which has been made in the production, perfection, 

 and application of the two most prominent of modern explosive agents, 

 nitro-glycerine and gun-cotton. Discovered at nearly the same time, 

 less than forty years ago, the one speedily attained great prominence, 

 on account of the apparent ease with which it could be prepared and 

 put to practical use ; a prominence short-lived, however, because the 

 first, and somewhat rash, attempts to utilise it preceded the acquisition 

 of sound and sufficient knowledge of its nature and properties. Even 

 many years afterwards, when the difficulties attending its employ- 



