84 On Recent Progress in the Firstory of 
magazines, or to the crews of merchant vessels in which 
gunpowder (for blasting purposes, &c.), is transported, as 
to compensate fully for the inconvenience attending the 
great increase of volume of the powder, there is no doubt 
that such a treatment of gunpowder actually issued for 
military and naval service would be attended by more than 
one serious obstacle; such as, the tendency of the powder, 
unless very largely diluted, to separate from the glass, 
during transport by land or sea, to so considerable an ex- 
tent as very greatly to diminish the degree of security 
originally aimed at; the very great addition which would 
have to be made to the arrangements for carrying the 
necessary ammunition, in active service; the necessity for 
introducing, in the field, or on board ship, the operations of 
separating the powder from the glass, and transferring it to 
cartridges and shells (which, whatever siftings and other 
arrangements were adopted, would be time-taking andvery 
dangerous), instead of preserving the ammunition ready for 
immediate use; and, above all, the incalculable mischeif 
which would inevitably result from the establishment, in 
the minds of the soldier and sailor, of an erroneous feeling 
of security in dealing with gunpowder, which, however 
harmless it may for a time be rendered, must finally be 
handled by the men in its explosive form. The extremely 
rare occurrence of accidents with gunpowder, on board ship 
or in active land service, is mainly due to the strictest en- 
forcement of precautionary regulations, some of which may 
appear at first sight exaggerated, or almost absurd, but 
which combine to maintain a consciousness of danger and 
a consequent vigilance indispensable to safety. 
One of the mostremarkable materials recently employed 
to replace gunpowder as a destructive agent, is nitro-gly- 
cerine. This substance was discovered by Sobrero, in 
1847, and is produced by adding glycerine in successive 
small quantities to a mixture of one volume of nitric acid 
of sp. gr. 1°43, and two volumes of sulphuric acid of sp. gr. 
1°83. The acid is cooled artificially during the addition of 
glycerine, and the mixture is afterwards poured into water, 
when an amber colour oily fluid separates, which is insolu- 
ble in water, and possesses no odour, but has a sweet 
pungent flavour, and is very poisonous, a minute quantity 
placed upon the tongue producing violent headache, whieh 
lasts for several hours. 
The liquid has a specific gravity of 1°6, and solidifies at 
about 4°-C. (50° F.); if flame is applied, nitro-glycerine 
