110 On the properties and uses of Gun-cotton, 



lower than gunpowder, which required a heat of 575° in order to 

 explode it. This was proved by placing portions of each on paper 

 and holding them over a jet of gas, when the cotton exploded without 

 the gunpowder. Any substance in the slightest state of ignition 

 would suffice to kindle it, and it would be observed that it left no 

 residue whatever. Its explosion took place more rapidly than that of 

 gunpowder. This was ingeniously illustrated by laying equal trains 

 of each on a board, the trains running in opposite directions, and 

 touching only at one point, i. e. the centre. A little detonating 

 powder was placed at the extreme end of each train in order to 

 indicate by sound the difference in the time of explosion. The trains 

 were fired by applying a hot iron to the central point where they 

 met : the gun-cotton burnt with much greater rapidity than the 

 powder, and there was a distinctly perceptible interval between the 

 detonations at the two ends. It was also evident, that while the 

 powder produced a visible smoke in burning, there was no visible 

 vapour from the cotton. Although so highly explosive, gun-cotton 

 presented an anomaly ; for if a train of it were firmly pressed in the 

 centre by any hard body, it might be ignited on one side without 

 the explosion being communicated to the other half. This experi- 

 ment was successfully shown. A portion of cotton was then placed 

 on an anvil, and it was proved that by a smart blow it easily and 

 entirely exploded on percussion. The electric spark would ignite it, 

 but the same precaution was required as in the case of gunpowder. 

 i. e. to slacken the course of the electric fluid by making it pass 

 through water, or it produced no effect. The cotton might be made 

 to explode in vacuo, but without any report, showing that air was not 

 absolutely necessary to its combustion. This fact was illustrated by 

 placing a small portion in a receiver provided with wires through 

 which the electric spark could be easily passed, and made to traverse 

 the cotton. When the receiver was exhausted, the discharge was 

 made : a very faint diffused light appeared at the time of explosion, 

 but there was no sound, nor was there any residue. The cotton, 

 therefore, contains enough oxygen for its own combustion. The 

 height of the barometer after the explosion would indicate the quan- 

 tity of gases evolved from a given weight. These gases had been 

 found by analysis to be carbonic acid, carbonic oxide, deutoxide of 



