THE HISTOET OE EXPLOSIVE AGENTS. 
501 
immersed in water, was violently exploded by a fulminate-fuse which was placed by its 
side, with about 0'25 inch of intervening water. In this instance, therefore, the ex- 
ploding power of the fuse was not absorbed by the envelope which enclosed the gun- 
cotton. 
Some nitroglycerine, contained in a glass beaker, was placed at the bottom of a trough 
filled with water ; a fulminate-fuse, placed at a distance of 2 inches from the side of the 
beaker, failed to fire the nitroglycerine ; but when the intervening water was reduced to 
little more than 1 inch, the detonation of the fuse exploded the nitroglycerine. 
A 12-pound cast-iron shell (0 - 75 inch thick, and 4'45 inches internal diameter) was 
filled about one-half with small granules of gun-cotton impregnated with nitroglycerine. 
The shell was then filled with water, and a waterproof fulminate-fuse was inserted 
through the plug which closed the shell. The fuse and each separate granule of the 
explosive agent were therefore surrounded by water. Upon ignition of the fuse, the 
shell (which was placed in a very strong room) exploded with a violent report, and was 
broken into very small fragments, the greater number of which were buried in the 
timber which lined the cell. 
A similar shell was half filled with the same explosive agent ; the spaces between the 
granules and the empty portion of the shell were then filled with a thin plaster of Paris 
mixture, and a fulminate-fuse was imbedded in the solid plaster which filled the upper 
half of the shell. The explosion of the fuse was attended by a precisely similar result 
to that obtained in the preceding experiment. 
It is believed that these experiments, together with the facts regarding the behaviour 
of gun-cotton which have been stated in the earlier part of this paper, afford convincing 
proof that the violent explosion of gun-cotton and nitroglycerine through the agency of 
a detonating fuse must be ascribed either to the mechanical effect of that detonation 
(i. e. to the work done upon the particles more immediately exposed to the blow or con- 
cussion of the detonation), or to the development of a disturbance of chemical equili- 
brium in the explosive agent by the suddenness and peculiar character of the concussion, 
or by the powerful vibrating impulse which the detonation establishes. 
The readiness and certainty with which gunpowder, gun-cotton, and other explosive 
substances may be detonated through the agency of a blow from a hammer or a falling 
body, are regulated by several circumstances ; they are in direct proportion to the weight 
of the falling body, to the height of its fall, or the force with which it is impelled down- 
wards, to the velocity of its motion, to the mass and rigidity, or hardness, of the support 
or anvil upon which the body falls ; to the quantity and mechanical condition of the 
explosive agent struck, and to the ready explosibility of the latter. Thus a sharp blow 
from a small hammer upon an iron surface will detonate gunpowder with very much 
greater certainty than the simple fall of a heavy hammer, or than a comparatively weak 
blow from the latter. It is very difficult, by repeated blows applied at very brief 
intervals, to ignite gun-cotton, if placed upon a support of wood or lead, both of which 
materials yield to the blow, the force set into operation by that blow being transferred 
through the explosive agent and absorbed in work done upon the material composing 
