the
ball weighed. Thus, a 30-pounder culverin would get 30 pounds of
powder. Since a 60-pounder battering cannon, however, had in
proportion a third less metal than the culverin, the charge must also
be reduced by a third--to 40 pounds!

[Illustration: Figure 16--GUNPOWDER. Black powder (above) is a
mechanical mixture; modern propellants are chemical compounds.]

Other factors had to be taken into account, such as whether the powder
was coarse-or fine-grained; and a short gun got less powder than a
long one. The bore length of a legitimate culverin, said Collado, was
30 calibers (30 times the bore diameter), so its powder charge was the
same as the weight of the ball. If the gunner came across a culverin
only 24 calibers long, he must load this piece with only 24/30 of the
ball's weight. Collado's _pasavolante_ had a tremendous length of some
40 calibers and fired a 6- or 7-pound lead ball. Because it had plenty
of metal "to resist, and the length to burn" the powder, it was
charged with the full weight of the ball in fine powder, or
three-fourths as much with cannon powder. The lightest charge seems to
have been for the pedrero, which fired a stone ball. Its charge was a
third of the stone's weight.

In later years, powder charges lessened for all guns. English velocity
tables of the 1750's show that a 9-pounder charged with 2-1/4 pounds
of powder might produce its ball at a rate of 1,052 feet per second.
By almost tripling the charge, the velocity would increase about half.
But the increase did not mean the shot hit the target 50 percent
harder, for the higher the velocity, the greater was the air
resistance; or as Mueller phrased it: "a great quantity of Powder does
not always produce a greater effect." Thus, from two-thirds the ball's
weight, standard charges dropped to one-third or even a quarter; and
by the 1800's they became even smaller. The United States manual of
1861 specified 6 to 8 pounds for a 24-pounder siege gun, depending on
the range; a Columbiad firing 172-pound shot used only 20 pounds of
powder. At Fort Sumter, Gillmore's rifles firing 80-pound shells used
10 pounds of powder. The rotating band on the rifle shell, of course,
stopped the gases that had slipped by the loose-fitting cannonball.

Black powder was, and is, both dangerous and unstable. Not only is it
sensitive to flame or spark, but it absorbs moisture from the air. In
other words, it was no easy matter to "keep your powder dry." Dur