THE HISTOEY OE EXPLOSIVE AGENTS. 
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further end was shattered and dispersed, portions of it being sometimes inflamed as the 
length of the tube used approached 3 feet. With such a tube much of the gun-cotton 
at the far extremity was scattered in a burning state ; but a partial detonation of the 
mass was obtained, as indicated by the shattering of the extremity of the iron tube 
against which it rested. The experiment was repeated with a tube of the same length 
(3 feet), the disks of gun-cotton being just inserted into each extremity : a partial 
detonation of the second disk again occurred, portions being dispersed and inflamed. 
Similar results were obtained with tubes ‘760 metre (2 feet 6 inches) long, except that 
the portion detonated was more considerable, 4 inches of the iron tube being broken up 
at that extremity. In order to ascertain that the shattering of the tube at the opposite 
end to that in which the initiative detonation was produced was really due to a partial 
detonation of the gun-cotton, and not to the check experienced by the rush of gas 
through the tube upon its encountering the obstacle presented by the disk or plug of 
gun-cotton, the following experiment was made. A cylindrical plug of wood, fitting 
loosely into the tube, was inserted at one extremity, and a disk of gun-cotton (1 ounce 
= 3T2 grms.) was introduced into the other end and detonated: the wooden plug 
was entirely broken up into small splinters, which were scattered about, but the end of 
the tube containing it was not injured. A similar experiment was made with a tube 
C feet 6 inches (2 metres) long, a wooden plug being inserted at one end, and a cart- 
ridge of dynamite weighing 2 ounces = 62-4 grms. exploded in the other extremity*: 
in this case also the wood was reduced to small splinters, but the tube at that end 
was not injured. The shattering of the tube at the far end in the preceding experi- 
ments was therefore conclusive evidence of a detonation of the gun-cotton, or of some 
* A remarkable illustration upon a large scale, but analogous to these experiments with tubes, of the work 
which a wave of gas set in motion by an explosion will accomplish when resistance is opposed to it was fur- 
nished by an experiment made a short time back at Portsmouth in reference to the application of compressed 
gun-cotton to the rapid demolition of fortifications. 
Among the old works required to be demolished was an arched “ Counterscarp Gallery ” of curved form, 
250 feet in length, 7 feet wide, and of a total height of 7 feet 4 inches. The arch was of 120° and 18 inches 
thick ; the back wall and part of the arched roof abutted upon solid earth ; the front wall was from 5 feet to 
5 feet 9 inches thick, and was pierced with nineteen oblong conical openings or “ loopholes,” the inner dimen- 
sions of which were 3 feet 2 inches by 5 inches. Each end of the gallery had a doorway 6 feet high and 
2 feet 9 inches wide, provided with a wooden door, outside which was a grating composed of iron bars 1 inch 
thick, framed together so as to be 4 inches apart. 
Three charges of compressed gun-cotton, weighing 20 pounds each, were arranged for simultaneous explosion 
in this gallery by means of electric detonating fuses ; they were quite unconfined, being simply suspended side 
by side against the outer wall, between two of the loopholes, at a short distance from one extremity of the 
gallery. By the detonation of these charges the gallery at this end was destroyed to a distance of about 60 feet ; 
and the brickwork was fissured to a much greater distance, the front wall being partly pushed forward up to a 
length of about 140 feet. At the other end of the gallery, where the wave of gas was checked or brought up, 
the. destruction accompanied by the explosion was nearly equal in extent to that effected at the seat of the 
charges ; the arch of the gallery was destroyed to a distance of about 70 feet, and the front wall was pushed 
forward to a length of about 80 feet. The bars of the iron grating which closed the entrance into the gallery 
at this end were twisted up into fantastic shapes, and projected to considerable distances. 
