THE ROYAL ARTILLERY INSTITUTION. 
137 
the rapid and more complete combustion of the gun-cotton, the momentary 
extinction of the gases, and the continuous abstraction of heat by them as 
they escape from the point of combustion, render it impossible for the 
gun-cotton to continue to burn otherwise than in the slow and imperfect 
manner, undergoing a transformation similar in character to destructive 
distillation. 
These facts appear to be fully established by the following additional 
experimental results:—■ 
(1) If, instead of employing in the above experiments a moderately com¬ 
pact gun-cotton-twist, one of more open structure is used, it becomes diffi¬ 
cult or even impossible to effect the desired change in the nature of the 
combustion, by the means described, because the gases do not simply bum 
at, or escape from, the extremity of the twisted cotton, but pass readily 
between 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 combustion 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 w r ire heated to full redness. 
