360 
ME. F. A. ABEL’S CONTRIBUTIONS TO 
condition. Similar results were obtained in operating upon small slabs of gun-cotton 
•0025 metre (0-1 inch) thick and *025 m. (1 inch) square, which were placed between 
smooth and level bronze plates, and subjected to blows from a falling weight. 
In some experiments made with the object of investigating, from a new direction, the 
action of a blow in producing explosion, some slabs and disks of compressed gun-cotton 
of different weights and thicknesses were fired at from a Martini-Henry rifle at distances 
ranging from 120 to 300 feet. In these experiments the impact of the bullet deter- 
mined, in a few instances, the complete explosion of the mass ; but in others, when 
circumstances combined to diminish the detonative power of the blow, a comparatively 
slight explosion was produced, and the greater portion of the mass fired at was violently 
scattered in small particles, which sometimes were inflamed. The complete or partial 
explosion of the mass of compressed gun-cotton was effected either when the thickness 
of the mass which was freely suspended in air was sufficient to cause it to oppose more 
or less effectual resistance to the penetrative power of the rifle-bullet, or when the slab 
of gun-cotton fired at rested closely against an iron plate. In the one case, the particles 
of gun-cotton actually struck by the projectile were effectually prevented from yielding 
to motion or mechanical dispersion at the moment of impact, by the support which the 
considerable surrounding mass of gun-cotton afforded them ; in the other instance, the 
rigid iron support, or backing, of the thinner masses of gun-cotton operated in a similar 
way in causing the effects of the blow to be concentrated upon, or confined to, the por- 
tions of gun-cotton actually struck by the bullet. Hence the effect of its impact was in 
both instances quite similar to that of a blow from a hammer applied to some portion 
of a piece of compressed gun-cotton placed upon an anvil ; the particles struck by the 
hammer are prevented from taking up the motion of the striking body by the rigid 
support or anvil ; chemical disintegration or explosion consequently takes place 
instead of mechanical dispersion, which would occur if less resistance were afforded to 
the motion of the hammer or projectile. At the instant of explosion the particles of 
matter which are undergoing transformation are confined between the striking body 
and the support (whether the latter be of metal or of gun-cotton); the resulting gas 
suddenly generated therefore escapes under great pressure, and scatters the contiguous 
particles of gun-cotton, sometimes even before these, or any large proportion of them, 
can become inflamed. In rare instances, as above stated, the explosion of the entire 
mass of gun-cotton followed upon the impact of the bullet ; such an explosion did not, 
however, give rise to the sudden development of force (and consequent destructive 
effects) obtained by the detonation of similar or even much smaller quantities of gun- 
cotton, as was demonstrated by placing the masses fired at upon iron plates, which 
remained uninjured, but would have been indented or fractured had the gun-cotton 
been detonated in the usual way when in contact with them. These comparatively 
feeble but complete explosions of the gun-cotton masses were most probably due to 
some very exceptional peculiarities in the physical condition of the disks or slabs, which 
