Explosives . uation of the form v = cpx, where p is the pressure and c and x are ordinary black powder x —= 0-f>, for highly compressed black prism powder033, for brown prism powder 0-25, for Poudre B 0-67, and for powder con-taining 50 per cent, nitro-glycerine Mansell - and Petavel8 prefer anequation of the form v = a0 -\-ap, where a0 is the rate of burning when t hereis no pressure, and a is the rate of increase of burning per unit of cordite a0 = 0-5 cm. per sec. and a = 0-018 cm. per sec. per the burning proceeds uniformly by layers is
Explosives . uation of the form v = cpx, where p is the pressure and c and x are ordinary black powder x —= 0-f>, for highly compressed black prism powder033, for brown prism powder 0-25, for Poudre B 0-67, and for powder con-taining 50 per cent, nitro-glycerine Mansell - and Petavel8 prefer anequation of the form v = a0 -\-ap, where a0 is the rate of burning when t hereis no pressure, and a is the rate of increase of burning per unit of cordite a0 = 0-5 cm. per sec. and a = 0-018 cm. per sec. per the burning proceeds uniformly by layers is shown by the fact thaiif a gelatinized powder be fired from a gun, which is too short to allow of thetotal consumption of the explosive, the remains of the grains thrown fromthe muzzle are found to be in every way similar to the original grains, exceptthat the dimensions are reduced. 1 Vermin, Poudres et Explosifs, p. 72. a Phil. Trans., 1907, 207a, p. 243. 3 Proc. , 79a, p. 277; , 1908, p. L66. 310. Fio. 61. Projectile and Powder Charge for American 16-inch GunWeight of Charge, 666-5 lb. nitro-cellulose powder (From Smithsonian Report, 1914, p. 256) 311 312 EXPD»MVK- The result of this is that with a powder made in the form of cords or cubesthere is a diminution of the burning surface a- the combustion of the chargeproceeds, and consequently the pressure falls off rapidly as the projectileapproaches the muzzle, although not so much a- was the case with blackpowder, which being porous did not burn entirely by parallel surfaces. Inr«ler to overcome this objection other forms are often adopted for the grainsof powder. If a strip or Make be used, the width of which i- great comparedwith the thickness, the area of surface remains practical! H <nt until the material i- entirely consumed. It has been found, however, that powdersmade up in these rlat form- are liable to irregular ballistics, and this hasbeen ascribed to the obstacles in the way of regular igniti
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