494 
ME. E. A. ABEL’S CONTRIBUTIONS TO 
A piece of very thin platinum wire, stretched across between the terminals of two 
insulated copper wires, was immersed in nitroglycerine; these wires were connected 
with a Bunsen battery of five large cells, and a second piece of platinum-wire, similar 
to that immersed in the liquid, was introduced into the circuit. This was then com- 
pleted, with the intervention of a long piece of platinum-wire between one of the con- 
ducting-wires and the battery. The resistance presented by this interposed platinum- 
wire was gradually reduced by shortening it, until ultimately the short platinum- 
w r ire not immersed in the nitroglycerine was fused. The latter was not exploded nor 
inflamed, nor was the wire enclosed in it fused, the heat developed in the latter being 
rapidly absorbed by the surrounding liquid and removed by convection. A very much 
thicker platinum-wire was now substituted for the thin one and immersed in the liquid ; 
a second short piece was not interposed in the circuit in this instance, but a long plati- 
num-wire, of the same thickness as the above, was employed, as a means of gradually 
reducing the resistance in circuit. When the length of this wire had been reduced to 
5 inches, it was raised to bright redness ; this state of things was maintained for about 
one minute, but the short wire in the nitroglycerine did not glow at the expiration of 
that period, nor did the liquid exhibit any signs of change, but the glass vessel contain- 
ing it had become very warm. The long platinum-wire was then removed, and the full 
battery-power was passed into the short wire immersed in the liquid. After the lapse 
of about one minute the latter began to assume a brownish colour (like that of a solution 
of iron), which rapidly deepened, though no red vapours were perceptible in the upper 
portion of the vessel, until after the lapse of 90 seconds, when the nitroglycerine 
•exploded with great violence. 
Attempts were afterwards made to explode nitroglycerine by means of the electric 
spark. The bare terminals of two insulated wires were immersed in the liquid, in close 
proximity to each other, and it was endeavoured to pass charges from a Leyden jar ; but 
the insulating power of the liquid prevented the passage of the spark between the 
immersed points. These were then arranged so as to barely touch the surface of the 
liquid, and powerful sparks were several times passed, hut without result. The sparks 
from a Ruhmkorfe coil with a Leyden jar attached were then allowed to pass uninter- 
ruptedly between the poles, which were just touching the liquid, the latter being splashed 
up by the discharges. In a few seconds the surface of the liquid darkened, and in 30 
seconds it exploded. 
It is evident from these results that nitroglycerine can only be exploded by electric 
agency or by direct application of any other source of heat, if the intensity of the latter, 
or the period during which it is applied, suffices to develope decomposition in some 
portion of the liquid ; ~when once this is established, the temperature is soon raised by 
accumulation of heat (especially if the application of external heat be continued) until it 
attains the point at which explosion occurs*. 
* In experiments instituted some time since on the action of heat upon nitroglycerine, I found that a small 
quantity (one or two drops) of pure nitroglycerine, if exposed to a very gradually increasing temperature, might 
he raised to 193° C. (380° E.) without the occurrence of an explosion ; the liquid sustained slow decomposition 
