THE HISTORY OE EXPLOSIVE AGENTS. 
371 
preparations) when employed wet. It appears, therefore, that the diminution in the 
expansion of the gases generated, consequent upon the expenditure of heat in the con- 
version of water into vapour, must be counterbalanced by the additional volume of 
vapour which the water furnishes. Indications were, however, obtained, in the compa- 
rative experiments with large charges, that when gun-cotton (or the nitrated material) 
is employed in the wet state its detonation is somewhat sharper or more sudden than 
when used dry ; and this is in accordance with the previous observation, that the less 
susceptible a mass of given explosive material is of compression, when submitted to the 
action of a sufficient initiative detonation, the more readily will detonation be trans- 
mitted, and the more sudden will the transformation take place from solid to gas and 
vapour. Hence, when the air is replaced by water, in a mass of compressed or nitrated 
gun-cotton, the transmission of detonation, when once established, is favoured by the 
increased resistance of the particles to mechanical motion*. The conclusions drawn 
from the behaviour of wet gun-cotton in practical trials on a large scale were subse- 
quently confirmed in an interesting manner by the results of experiments on the rate 
with which detonation is transmitted by dry and wet gun-cotton. 
The change in structure which a mass of wet compressed gun-cotton sustains when 
its temperature is sufficiently reduced to freeze the water, affects its susceptibility to 
detonation in a remarkable, though readily explicable, manner. When the water is 
crystallized, the particles of gun-cotton are no longer uniformly and completely enclosed 
in the diluent ; but the dilution becomes similar in character to that of the mixtures 
of gun-cotton with soluble (crystallized) salts which have been described, and the wet 
gun-cotton (or rather gun-cotton diluted with solid water) becomes readily detonated 
by the ordinary means employed for exploding the air-dry substance. Thus gun-cotton 
cylinders in the moist condition in which they were removed from the hydraulic press, 
and others which had afterwards been soaked in water when frozen and reduced in 
temperature to — 9°-4 C. (17° F.), were found to be exploded with certainty by the 
fulminate- 44 detonators ” ordinarily used for exploding dry gun-cotton. 
Mercuric fulminate, and also the mixture of that substance with potassium chlorate 
and antimony tersulphide, which is employed in percussion-caps, were found to he 
readily detonated through the agency of dry confined fulminate when they were mixed 
with water in sufficiently large proportion to convert them into pasty masses. In the 
first instance, 5 grains (*325 grm.) of dry fulminate, enclosed in a capsule of sheet-tin, were 
found to detonate the wet fulminate and 44 cap-composition ” when surrounded by these. 
* In some recent submarine experiments, in which means were employed for accurately measuring the 
comparative force exerted by different explosions, produced under corresponding conditions (as to depth of 
submersion, confinement of charge, &c.), some gun-cotton of lower compactness than usual was found to furnish 
a somewhat low result when detonated in the dry state, but gave a decidedly high result when thoroughly 
saturated with water. In this case the comparatively porous gun-cotton, when its pores were filled up by 
water, was in a condition most favourable for sudden detonation. 
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