516 
CONTRIBUTIONS TO THE HISTORY OF EXPLOSIVE AGENTS. 
considerable than when the more gradual explosion of gun-cotton is brought about by 
the usual mode of firing. In the case of the detonation of gun-cotton imbedded in 
such material, the force which is applied with comparative suddenness is to a consider- 
able extent expended in the disintegration and compression of the surrounding material, 
before there is time for motion to be communicated through any considerable mass of 
the rock. 
A further indication of the difference in the rapidity of explosion of gun-cotton by 
detonation and by the simple application of heat is furnished by the difference in the 
luminous effect observed in the two instances. The ordinary explosion of gun-cotton is 
attended by a considerable body of flame, due to the ignition of the generated carbonic 
oxide ; but the detonation of gun-cotton is only attended by a sudden flash, which it is 
very difficult to observe in daylight if only small quantities are exploded. The trans- 
formation of the solid into gas appears, in fact, to be too sudden for the generated com- 
bustible gas to become inflamed. 
In conclusion, it may not be out of place to refer briefly to a few illustrations of the 
important bearings which the new mode of developing the explosive force of gun-cotton 
has upon the practical uses of the material as a destructive agent. The confinement 
of a charge of gunpowder or gun-cotton in a blast-hole, by firmly closing up the latter 
with earth, powdered rock, or other compressible material (by the process known as 
tamping or stemming) to a depth greater than the line of least resistance opposed to 
the action of the charge, is essential to the success of a blasting operation ; but the great 
rapidity of explosion, by detonation, of a charge of gun-cotton greatly reduces the value 
of this operation ; the destructive effect of the material, when exploded in a hole which 
is left open, is not inferior in extent to that obtained by similarly exploding a charge 
confined in the usual manner. Thus the most dangerous operation in connexion with 
blasting may be entirely dispensed with*. In submarine operations, it is no longer 
necessary to enclose the charge of explosive agent in the strong and therefore cumber- 
some metal receptacles hitherto required to ensure the full development of its explosive 
force ; the destructive action of a charge of gun-cotton, enclosed in a waterproof bag or 
thin glass vessel and exploded by detonation, being decidedly greater than that furnished 
by a corresponding charge confined in a strong iron vessel and exploded by flame. Small 
charges of gun-cotton simply resting upon the upper surfaces, or loosely inserted into 
natural cavities, of very large masses of the hardest description of rock or of iron, have 
broken these up as effectually as if corresponding charges had been firmly imbedded in 
the centre of the mass and exploded in the usual manner. Lastly, the certainty, facility, 
and expedition with which certain important military destructive operations may be 
accomplished by means of gun-cotton exploded by detonation, are not among the least 
important advantages which are now secured to this interesting and remarkable explo- 
sive agent. 
This observation does not apply equally to large charges, such as are used in some military operations, for 
the placing of which it is necessary to sink or drive shafts or openings of large dimensions. 
