49 



in Abel's process, which is now used on a very large scale 

 in the government factory at Waltham Abbey, but will 

 proceed to demonstrate some of the properties of gun cotton. 



Properties of gun cotton as compared with gunpowder : 



(i.) Inflames at a temperature of about 300 P., or 

 roughly speaking at a temperature half as high as that re- 

 quired to fire powder. This is seen when I touch gunpowder 

 with a glass rod heated to the above-mentioned temperature 

 I fail to ignite it, but gun cotton is immediately ignited 

 by the same rod. 



(2.) Gun cotton fired or exploded is unattended by 

 smoke, and leaves no apparent residue, the" small residue (i 

 to 2 per cent) being scattered by the explosion. This is 

 strikmgly illustrated by placing a tuft of dry gun cotton on 

 my hand and lighting, when no inconvenience is occasioned. 



(3.) The rate of ignition of gun cotton is much quicker 

 than that of gunpowder, in fact, I will fire a tuft of gun 

 cotton, placed on a heap of powder, without igniting the 

 lattei'. 



(4-) The recoil of a gun charged with gun cotton is less 

 than that for powder. The projectile velocity being equal 

 the recoil of the gun charged with gun cotton is only two 

 thirds that of powder. 



I will demonstrate the difference in recoil by floating 

 two porcelain crucibles on water, with the edge of each 

 crucible just above the water level. Into the first I introduce 

 seven grains of gun cotton, into the second, twenty-four 

 grains of powder (the weight giving projectile force equal to 

 that of the seven grains of gun cotton) and fire both with a 

 hot wire. The recoil of the powder submerges its crucible 

 and it smks to the bottom, whilst that containing the ^un 

 cotton continues to float. 



(5-) Gun cotton leaving only i or 2 per cent, of solid 

 residue, whilst gunpowder leaves nearly 60 per cent it 

 follows that the former used as a projectile agent heats 'the 

 gun but slightly compared with the latter. In practice it 

 has been found that a gun after firing a hundred rounds with 



