The Works Of Messrs. Schneider And Co.

POWDERS AND OTHER EXPLOSIVES. 321 facilitate tlieir general identification, as follows (Figs. 1025 to 1027): Cl) For fiele! and mountain guns, and, as a rule, C 2 f for all small calibre guns. S P 1 -j S P 2 > Foi’ siege and garrison guns, S P 3 J P B 1 'j P B 2 > For coast defence and naval guns. P B 3 J This is not, however, an absolute classification, and ir Service the uses to which the varions powders are put are not always those stated above. These powders are all of ternary composition ; their constituent parts—-sulphur, nitrocellulose; one of their characteristics is that they contain no trace of free nitro-glycerine, or of nitro-glycerine in the state of simple mixture. This distinguishes them from many other smokeless explosives. As a direct conséquence, the use of these powders does not entail any undue wear in the guns. Nitro-glycerine under high temperatures and pressures has a great erosive efiect on metals ; and in certain smokeless powders it is contained as a mixture and not in combination, being lielcl mechanically with the help of an absorbing ingrédient. The French smokeless powders are Chemical com- positions, and therefore their use does not give rise to any of the serions disadvantages among which we may 25 § kl Cases for Holding Cartridges and Prismatic Powder. saltpetre, and charcoal—varying in proportion, according to the quality required. The two first types are made in the shape of flat grains, the thickness of which differs according to the calibre of the gun. Tbe third is finished to a hexagonal shape. When these powders are delivered loose, i.e. not préparée! in charges ready for firing, they are packed in wooden cases lined with zinc, or in metallic chests with air-tight covers. Smokeless Powders.—These form the usual ammuni- tion for the Schneider-Canet guns ; they are of the quality known as “ French smokeless powders ” and contain the whole series of varieties for guns of all calibres, for naval and land service. They are made in rectangular strips, of a straw-colour, the section and length varying according to the dass of gun. These powders are préparée! from mention : the more or less rapid erosions in the bore, and their conséquences as regards the resisting power of the gun, and the précision of firing; exudation of free nitro-glycerine on the surface of the explosive, when the latter has remained for a time in store, and constituting a permanent danger of prématuré explo- sion which a simple shock might precipitate. Besid es this, these explosives maintain a longer stability as regards quality ; this quality has been proved by numerous tests and analyses carried out periodically on quantities in stock. On the other hånd, however, it has been remarked that the pressures being equal, they impart to the projectile a lower speed than do the explosives préparée! from nitro-glycerine. But this difference in speed is slight, and out of proportion to the advantages