496 
MR. E. A. ABEL’S CONTRIBUTIONS TO 
sion ; and although, in his published description of these various methods, he refers to 
difficulties in developing explosion by those which relate to the simple application of 
flame or other heated body to the nitroglycerine, yet he refers the effect produced by 
the confined charge or the percussion-cap only to the heat developed by the ignition of 
these exploding agents. 
The circumstance that nitroglycerine, or any preparation of that substance, may be vio- 
lently exploded when freely exposed to air, by the explosion in contact with it of a small 
necks which had been for some time previously undergoing decomposition (from long-continued exposure to 
temperatures considerably below its inflaming-point), was always very much greater than would have been the 
case had gun-cotton in the flasks been ignited by the momentary application of a highly heated body. It would 
appear, from temperature-observations carried on during experiments of this kind (Phil. Trans, vol. clvii. pp. 
197, 223, 226), that in those instances the great violence of explosion was to be ascribed in part to the rapid 
accumulation of heat in the mass of gun-cotton when the decomposition had reached particular stages ; but 
there can be no question that, at the period immediately preceding the explosion, the gun-cotton was in a state 
of high chemical tension, and readily susceptible of instantaneous chemical change throughout, just as a Rupert’s 
drop is readily susceptible of violent mechanical disintegration ; so that the passage from gradual to instanta- 
neous and therefore most violent decomposition, would occur as soon as the accumulation of heat attained the 
point at which a sufficient disturbing impulse was imparted to the mass. 
The following series of experiments appear confirmatory in their results of the conclusions drawn from the 
accidental results obtained in the experiments just alluded to. 
A wide test-tube was filled to about one-fourth with gun-cotton, the mouth of the tube was left open, and 
the gun-cotton was inflamed by means of a platinum- wire heated by electricity. A faint explosion was the 
result, accompanied by a considerable body of flame, and a portion of the gun-cotton was projected from the 
tube unburned. 
The experiment was repeated, the tube being immersed for several minutes in a water-bath at a temperature 
of 100° C., so that the gun-cotton was raised throughout to that temperature immediately before it was inflamed. 
The explosion was decidedly, though not very greatly, more vehement than before ; the tube was not shattered. 
A broad piece of thin platinum-foil, about 2 inches long, was attached by its two sides to copper wires leading 
to the poles of a battery, sufficient resistance being introduced into the circuit to prevent the foil from being 
raised to a higher temperature than 90°-100° when the circuit was completed. The wires were approached to 
each other, so that the strip of foil formed a species of tube open at both ends and down the side. A similar 
quantity of gun-cotton to that used in the preceding experiments was placed inside this tube, being therefore 
nearly surrounded by the foil. The whole arrangement was then introduced into a test-tube, like those used 
in the preceding experiments, and the voltaic circuit was completed. In the course of a few minutes the odour 
of decomposing gun-cotton was perceptible at the opening of the tube ; faint nitrous vapours were soon after- 
wards observed, and within about fifteen minutes after the first application of heat, the gun-cotten exploded 
very sharply with only a faint flash, and the tube was shattered and violently dispersed. 
The great violence of the explosion at Woolwich, in 1866, of about 140 lbs. of gun-cotton which had been 
exposed to elevated temperatures for ten months, and of which some packages, very imperfectly purified, were 
known to be in a state of decomposition at the time (Phil. Trans, vol. clvii. p. 243 et seep), can scarcely be only 
ascribed to the circumstances that the gun-cotton had been closely packed in strong cases, and that the packages 
of gun-cotton were at a temperature of about 50° C. at the time of the explosion. When the decomposition, 
established in some small portion of the gun-cotton, had attained the condition resulting in explosion, a large 
quantity of the material was in a state of incipient change and, therefore, in a favourable condition for sudden 
metamorphosis ; and this circumstance must have greatly contributed to the suddenness and consequent violence 
of the explosion. 
