THE HISTOEY OE EXPLOSIVE AGENTS. 
361 
favoured the transmission of ignition from the point where explosion was produced by 
the blow to the whole of the surrounding portions of gun-cotton at the instant when 
they were undergoing dispersion. The resulting transformation of the solid into gas, 
though sufficiently rapid to produce the oral effect of an explosion, must be very gradual 
as compared to that which attends a detonation, and the destructive effects exerted 
must in consequence be comparatively unimportant*. 
The manner in which resistance to mechanical motion favours the chemical disinte- 
gration or explosion of the portions of a compact mass of gun-cotton which is sub- 
jected to a blow, as from the impact of a bullet, was conclusively demonstrated by 
a series of experiments with gun-cotton disks of the same density and diameter, but 
differing in thickness, and therefore in weight. These disks had strings fastened 
round their circumference by which they were freely suspended; they were fired at 
from a Martini-Henry rifle with hardened lead bullets, the marksman being stationed 
at a distance of 100 yards from the gun-cotton which served as a target. Disks which 
weighed 4 ounces and 8 ounces were perforated by the bullet, not a particle of the gun- 
cotton being even ignited, and these results were repeatedly obtained. Disks weighing- 
12 ounces were inflamed when struck by the bullet, but not exploded ; whilst disks 
weighing 16 ounces, fired at under the same conditions, were exploded, portions being, 
in some instances, dispersed in a burning state. The resistance opposed to the flight 
of the bullet, even by the 8-ounce disks, was insufficient to cause such retardation of 
the projectile during its penetration of the mass as to develop sufficient heat to inflame 
the gun-cotton ; with the 12-ounce disk the resistance to motion offered by the particles 
in the bullet sufficed, during the penetration of the mass, to develop the heat necessary 
for its ignition ; while the penetration of the bullet was opposed by the mass of the 
16-ounce disk to a sufficient extent to cause the operation of the force conveyed by the 
projectile to be concentrated, at the instant of impact, upon the particles immediately 
in front of it, which therefore were suddenly transformed into gas or exploded. 
By attaching a piece of soft wood, 0'4 inch thick, to one of the faces of a disk 
weighing 8 ounces, which was suspended as in the former experiments, the surface 
being fired at from a distance of 100 yards, the flight of the bullet was so far retarded 
by the resistance which the wood opposed in the first instance, that its subsequent 
penetration of the gun-cotton was effected comparatively slowly, and the heat developed 
by the further retardation of the bullet inflamed the gun-cotton, while in former experi- 
ments with unprotected disks of the same size these were perforated without any 
instance of ignition. 
Wooden boxes containing compressed gun-cotton, both loosely and closely packed, 
have been repeatedly fired at from rifles ; generally the contents of the box were in- 
flamed, but in no instance was an explosion produced. Similar packages containing 
* An interesting confirmation of this difference between explosion and detonation was obtained in subse- 
quent experiments made with the view of determining the rate at which detonation is transmitted through 
tubes, which are described in the concluding portion of this Memoir. 
MDCCCLXX1V. 3 B 
