1872.] Modern Cannon Powder. 61 
but when once inflamed burn very rapidly. It is necessary 
to draw a clear distinGtion between a rapidly igniting and a 
quickly burning powder: this difference will be more apparent 
when we come to the discussion of more modern powders. 
The grains in both L.G. and R.L.G. powder are very 
irregular in shape, and the latter is double the size of the 
former, so that the individual grains will burn more slowly. It 
was, therefore, believed on theoretical grounds that the larger 
powder would exert a less violent strain upon a gun, and it 
was adopted, as we have said, for our rifled guns, the 
question of density being regarded at that time as of minor 
importance, though it was already attracting some attention. 
It has since been conclusively proved by experiments that 
the density and hardness of the grains of powder are of quite 
as vital importance as their size and form, in determining 
the rate of ignition and combustion of a charge. 
The density depends on the amount of pressure to which 
the powder meal has been subjected during manufacture, 
while the hardness is greatly affected by the amount of 
moisture present in the meal when pressed; one term 
applies to the mass, while the other refers more particularly 
to the surface of the grains. A dense powder may be 
generally stated to be a slow-burning powder, while a hard 
one is slow lighting. Density retards the combustion both 
because there is more matter in the same volume, and con- 
sequently more powder to be consumed in proportion to the 
ignited surface of the grain, and also because the heated gas 
finds greater difficulty in penetrating the solid mass of the 
grain. A hard powder need not of necessity be very dense; 
it is even possible, by pressing it in a moist state, to obtain 
a very hard powder which shall at the same time be light 
and porous in the interior of the grains. Such is the 
Russian prismatic powder (of which more hereafter), and it 
may be taken as a good specimen of a slow lighting but 
quick burning powder. 
With the improved appliances now used in testing powder, 
the quality of the large stock of L.G. and R.L.G. in store 
in this country has been found to be very variable, prin- 
cipally due to variation in the density of different brands. 
Previous to the year 1868, the proof to which all cannon 
powders were subjected was very imperfect, and failed 
utterly in ensuring uniformity in those passed into the 
service. The density was only roughly ascertained by the 
process of ‘‘ cubing,” as it was called, while the strength 
and uniformity of the powder was tested by the “‘ Mortar 
Eprouvette.” ‘‘Cubing” consisted in weighing a cubic 
