g, with these outside proportions:

1st reinforce = 2/7 of the gun's length.
2d reinforce = 1/7 plus 1 caliber.
chase = 4/7 less 1 caliber.

The trunnions, about a caliber in size, were located well forward
(3/7 of the gun's length) "to prevent the piece from kicking up
behind" when it was fired. Gunners blamed this bucking tendency on the
practice of centering the trunnions on the _lower_ line of the bore.
"But what will not people do to support an old custom let it be ever
so absurd?" asked John Mueller, the master gunner of Woolwich. In 1756,
Mueller raised the trunnions to the _center_ of the bore, an
improvement that greatly lessened the strain on the gun carriage.

[Illustration: Figure 26--EIGHTEENTH CENTURY CANNON, a--Spanish
bronze 24-pounder of 1746. b--French bronze 24-pounder of the early
1700's. c--English iron 6-pounder of the middle 1700's. The 6-pounder
is part of the armament at Castillo de San Marcos.]

[Illustration: Figure 27--SPANISH 24-POUNDER CAST-IRON GUN (1693).
Note the modern lines of this cannon, with its flat breech and slight
muzzle swell.]

The caliber of the gun continued to be the yardstick for "fortification"
of the bore walls:

Vent 16 parts
End of 1st reinforce 14-1/2 do
Beginning of second reinforce 13-1/2 do
End of second reinforce 12-1/2 do
Beginning of chase 11-1/2 do
End of chase 8 do

For both bronze and iron guns, the above figures were the same, but
for bronze, Armstrong divided the caliber into 16 parts; for iron it
was only 14 parts. The walls of an iron gun thus were slightly thicker
than those of a bronze one.

This eighteenth century cannon was a cast gun, but hoops and rings
gave it the built-up look of the barrel-stave bombard, when hoops were
really functional parts of the cannon. Reinforces made the gun look
like "three frustums of cones joined together, so as the lesser base
of the former is always greater than the greatest of the succeeding
one." Ornamental fillets, astragals, and moldings, borrowed from
architecture, increased the illusion of a sectional piece. Tests with
24-pounders of different lengths showed guns from 18 to 21 calibers
long gave generally the best performance, but what was true for the
24-pounder was not necessarily true for other pieces. Why was the
32-pounder "brass