THE HISTOEY OE EXPLOSIVE AGENTS. 
377 
sion may be exploded by detonation, with certainty, when mixed with water in different 
degrees of dilution, provided such mixtures be enclosed in a receptacle of sufficient 
strength. The detonation of 2 ounces of compressed gun-cotton, immersed in such 
mixtures, was without effect upon them when they w T ere only partially confined; 
but 1 ounce applied in the same way developed detonation when the mixtures were 
completely confined in the cast-iron shells. This result is not attained by the employ- 
ment of only 0’5 ounce of compressed gun-cotton as the detonator ; but more sensitive 
explosive agents than gun-cotton are susceptible of detonation, under the same condi- 
tions, by much smaller initiative charges. Thus 2 ounces of mercuric fulminate, 
placed in a 16 Pr. cylindro-conoidal shell, which was then filled up with water, was 
detonated by means of about 15 grains (1 grm.) of the fulminate confined in a sheet-tin 
case. Although the loose fulminate was in a small heap at the bottom of the shell, 
being separated from the lower extremity of the detonating tube (attached to the screw- 
plug of the shell) by a water-space of 0-75 inch ((M)18 m.), the shell was very uniformly 
broken up; 170 fragments were collected in the chamber, and 1 lb. 11 oz. (842‘4 grms.) 
were not recovered, being dispersed in minute fragments. 
The susceptibility of gun-cotton (and of other explosive bodies) to detonation in shells, 
when employed in admixture with water, as described, appears to have afforded the 
means of overcoming the hitherto insurmountable difficulty of employing violent but 
comparatively sensitive explosive agents in shells, with safety to the gun from which these 
are fired. Various plans have been devised, but hitherto without success, for preventing- 
charges of gun-cotton, in shells, from being exploded through the agency of the con- 
cussion to which the latter are subjected when fired from a gun, and the attempted 
application of nitroglycerine-preparations in shells has failed for the same reason. But 
mixtures of gun-cotton with water may be fired from guns in shells with absolute 
freedom from liability to premature explosion ; and it is now no longer doubtful that 
the desideratum of a simple and safe system of applying the violently destructive effects 
of gun-cotton in shells will be attained as soon as a safe adaptation of the mercuric 
detonating arrangement to the fuse of the shell has been perfected. 
VII. — ON THE VELOCITY OE DETONATION, OE THE BATE AT WHICH DETONATION 
IS TEANSMITTED. 
The very satisfactory results obtained by the Government Committee on explosive 
substances in employing the chronoscope, devised by Captain A. Noble, F.R.S., for 
determining the time occupied by a projectile in traversing different intervals in the 
bore of a gun, led me to avail myself of this instrument for estimating the velocity with 
which detonation is propagated or transmitted under various conditions. The con- 
struction and mode of using this chronoscope have been described in the preliminary 
Report of the Committee on Explosions issued by the War Office in February 1870. 
A few words may serve to give a sufficient explanation of the instrument for present 
purposes. A series of thin metal disks (36 inches in circumference), the edges of which 
MDCCCLXXIV. 3 D 
