1864] 



Gun-cotton and Gunpowder. 



215 



at, or escape from, the extremity of the twisted cotton, but pass readily be- 

 tween the separated fibres of the material, rendering it difficult or impos- 

 sible to divert them all into one direction ; and hence they at the same 

 time transmit the combustion from particle to particle, and maintain the 

 heat necessary for their own combustion. 



2. If a piece of the compactly twisted gun-cotton, laid upon the table, 

 be inflamed in the ordinary manner, and a jet of air be thrown against the 

 flame, in a line with the piece of cotton, but in a direction opposite to that 

 in which the flame is travelling, the combustioD may readily be changed to 

 the slow form, because the flame is prevented from enveloping the burning 

 cotton, and thus becomes extinguished, as in the above experiment. 



3. Conversely, if a gentle current of air be so directed against the gun- 

 cotton, when undergoing the slow combustion, that it throws back upon 

 the burning cotton the gases which are escaping, it will very speedily burst 

 into the ordinary kind of combustion. Or, if a piece of the gun-cotton- 

 twist, placed along a board, be made to burn in the imperfect manner, and 

 the end of the board be then gradually raised, as soon as the material is 

 brought into a nearly vertical position, the burning extremity being the 

 lowest, it will burst into flame. 



By applying to the extremity of a piece of the compact twist a heated 

 body (the temperature of which may range from 135° C. even up to a red 

 heat), provided the source of heat be not very large in proportion to the 

 surface presented by the extremity of the gun-cotton, the latter may be 

 ignited with certainty in such a manner that the slow form of combustion 

 at once ensues, the heat applied being insufficient to inflame the gases 

 produced by the decomposition of the gun-cotton. By allowing the gun- 

 cotton thus ignited to burn in a moderately wide tube, closed at one end, 

 the inflammable gases produced may be burned at the mouth of the tube, 

 while the gun-cotton is burning in the interior ; or they may be ignited 

 and the gun-cotton consequently inflamed, by approaching a flame, or a 

 body heated to full redness, to the latter, in the direction in which they 

 are escaping. 



It need hardly be stated that these results are regulated by the degree 

 of compactness of the gun-cotton, the size of the twist, and the dimensions 

 of the heated body. Thus a small platinum wire heated to full redness, 

 or the extremity of a piece of smouldering string, will induce the slow 

 combustion in a thin and moderately compact twist ; but a larger body, 

 such as a thick rod of iron, heated only to dull redness, will eff'ect the 

 ignition both of the gun-cotton and of the gases evolved by the combustion 

 of the first particles, so that the material will be inflamed in the ordinary 

 manner. Similarly the red-hot platinum wire, or a stout rod heated to 

 redness barely visible in the dark, if they are maintained in close proxi- 

 mity to the slowly burning surface of gun-cotton, will eventually cause the 

 gases evolved to burst into flame. The more compact the twist of the 

 gun-cotton, the more superficial is the slow form of combustion induced in 



