Professor Faraday on Gunpowder. 115 



they became white hot, and burnt on contact with it. That a higher 

 temperature was required for the explosion of gunpowder than of 

 gun-cotton, was further proved by heating a wire in a flame, placing 

 it on a mass of gunpowder, which did not ignite, and then passing it 

 rapidly onwards to a mass of gun-cotton, which immediately ex- 

 ploded. The Professor remarked, that there was a great difference 

 in the products of the two substances when burnt in the open air, — 

 the gases derived from gunpowder had a very high temperature, but 

 this was not the case with those resulting from 4he combustion of 

 gun-cotton. m 



The mere contact of flame will not readily ignite gunpowder. A 

 quantity of powder being placed on a plate, a gas flame was passed 

 repeatedly over it without igniting it ; and when it was allowed to 

 remain playing on the powder, several seconds elapsed before this 

 exploded : — in fact, it remained quiescent until it acquired the high 

 temperature requisite for its combustion. It was important, however, 

 to state, that the raising of the temperature of the smallest particle 

 would suffice to kindle the whole mass : it was by no means necessary 

 that all the particles should be simultaneously heated. The heat 

 given out, in its own combustion, was sufficient to convert the whole 

 into gaseous matter, and to expand the gases to such a degree as to 

 render them equal to from 3500 to 3800 atmospheres. The cause 

 of the rapid explosion of ordinary gunpowder was, that when one 

 particle was kindled, the heat and flame rapidly spread through the 

 interstices of the little spheres, and raised the temperature of each. 

 If the kindled particle were below, the flame spread upwards, if 

 above, downwards ; and each grain was, therefore, wrapped in a sheet 

 of flame, at a high temperature, within a very short interval of time. 

 Nevertheless, compared with fulminating compounds, the explosion 

 was not instantaneous but gradual, the clear interspaces between the 

 little spheres allowing the flame to penetrate the whole mass, and thus 

 to act with a progressively increasing force upon the projectile. 

 Supposing these interstices to be filled up, and the particles to be 

 closely packed, so as to be everywhere, in contact, the explosion is 

 slow, the gunpowder then burns only on the surface, and so it conti- 

 nues upwards or downwards until the whole is consumed. A piece 

 of gunpowder, in lump, was ignited : it burned rapidly, but without 



