252 ANNUAL REPORT SMITHSONIAN INSTIFUTION, 1914. 
extensive use in the mighty engines of destruction such as the sub- 
marine mine, the torpedo, and in projectiles thrown from cannon to 
great distances with marvelous accuracy, is resulting in loss of life 
and destruction of property on an unprecedented scale. 
BLACK POWDER, 
Black powder is extensively used for blasting and mining purposes, 
but has lost its importance as a propellant in modern firearms, al- 
though still retained for primers and other special purposes supple- 
mental to the more important smokeless powder. 
Black gunpowder has, however, played a very important part in 
the history of the wars of the past three centuries, and for that 
reason deserves more than brief mention. It is ordinarily com- 
posed of about 75 parts niter, 15 parts charcoal, and 10 parts sul- 
phur. The niter furnishes the oxygen to burn the charcoal and sul- 
phur. The charcoal furnishes the carbon and the sulphur gives 
density to the grain, and lowers its point of ignition. The earliest 
record of the use of a mixture of this general character in actual war 
dates back to the fourteenth century, but its use did not become 
common until about the beginning of the sixteenth century. Until 
about the end of that century it was used in the form of fine pow- 
der; hence the name. To overcome the difficulty experienced in 
loading small arms from the muzzle with such material, it was given 
agranular form. Little further marked improvement was made until 
about 1860, when Gen. Thos. Rodman, of the Ordnance Department 
of the United States Army, advanced the principle that the rate of 
combustion, and consequently the pressure developed, could be con- 
trolled by compressing the fine-grained powder previously used into 
larger grains of greater density. The size of grain was to be so pro- 
portioned to the size and length of the gun that the powder would be 
completely burned up about the time the projectile reached the 
muzzle. 
The increase in size of grain decreased the initial burning surface 
for a given weight of charge, thereby lowering the rate at which the 
gas was given off during the early part of the movement of the pro- 
jectile and correspondingly lowering the maximum pressure. This 
permitted the use of a bigger charge, without overstraining the gun, 
and thus secured higher average pressures along the bore with re- 
sultant higher muzzle velocities. This principle is of special impor- 
tance because it has found application in the manufacture of all the 
later gunpowders. 
BROWN POWDER AND SMOKELESS POWDER. 
A further reduction in the velocity of combustion of powder was 
obtaied about 1880 by the substitution of an underburnt charcoal 
