116 Professor Faraday on Gunpowder. 



sudden explosion, gave off torrents of gas, and moved from the part 

 where it was placed, being carried backwards by the force with which 

 the gas was evolved. The fusees used for exploding bombs were 

 nothing more than wooden cases, containing gunpowder closely 

 packed and ramed into them. When one of them was ignited, it 

 burnt steadily, without explosion. Had the wooden tube been filled 

 with gunpowder grains, the whole would have been blown to pieces. 

 These facts accounted for many curious and apparently anomalous 

 results obtained with gunpowder. The same material which burnt 

 slowly like a fusee out of a paper case, would sometimes explode 

 suddenly when confined in one. This was well known in pyrotechny, 

 although the cause might not be understood. A cylinder of gun- 

 powder, closely pressed, was taken from a case and ignited : it did 

 not burn with explosion, but was steadily consumed like a fusee from 

 the ignited end. "When a similar cylinder was ignited in its paper 

 case, the whole suddenly exploded. The Professor explained this by 

 stating that the gunpowder, when ignited at the mouth of the case, 

 stretched or expanded the sides of the paper tube, and the flame 

 could then travel along the whole surface of the cylinder of powder, 

 and thus heat to a high temperature every portion at once. Accidents 

 might arise from an ignorance of this principle. The miner's fusee 

 formed a familiar illustration of the effect of mechanical compres- 

 sion on the explosion of gunpowder. A long channel was made by 

 stretching pieces of string side by side, so as to form a kind of 

 trough. This was then filled with gunpowder. If in this state one 

 end were ignited, the whole would explode ; but the miner, wishing 

 the fusee to burn slowly and steadily, winds iron wire firmly round 

 the strings, so as to compress the grains of gunpowder into the 

 closest possible contact. A complete cylinder of metal, enclosing 

 gunpowder, flexible, and easily cut to any length for blasting pur- 

 poses is thus obtained. Professor Faraday here produced one of 

 these fusees. Two equal lengths were then taken: one piece was 

 fired at the end, and the powder burnt steadily through from end 

 to end without explosion ; the other piece was cut open, the powder 

 shaken out, and a heated wire applied to it, when the whole suddenly 

 exploded ; — thus proving that the powder had undergone no change, 

 but that the difference in the results was merely owing to the me- 



