e San Marcos
National Monument today appear to be seventeenth century Spanish
pieces. Most of the 24- and 32-pounder garrison cannon, however, are
English-founded, after the Armstrong specifications of the 1730's, and
were part of the British armament during the 1760's. Amidst the
general confusion and shipping troubles that attended the British
evacuation in 1784, some ordnance seems to have been left behind, to
remain part of the defenses until the cession to the United States in
1821.

The Castillo also has some interesting United States guns, including a
pair of early 24-pounder iron field howitzers (c. 1777-1812). During
the 1840's the United States modernized Castillo defenses by
constructing a water battery in the moat behind the sea wall. Many of
the guns for that battery are extant, including 8-inch Columbiads,
32-pounder cannon, 8-inch seacoast and garrison howitzers. St.
Augustine's Plaza even boasts a converted 32-pounder rifle.

[Illustration: Figure 29--VAUBAN'S MARINE CARRIAGE (c. 1700).]

Garrison and ship carriages were far different from field, siege, and
howitzer mounts, while mortar beds were in a separate class entirely.
Basic proportions for the carriage were obtained by measuring (1) the
distance from trunnion to base ring of the gun, (2) the diameter of
the base ring, and (3) the diameter of the second reinforce ring. The
result was a quadrilateral figure that served as a key in laying out
the carriage to fit the gun. Cheeks, or side pieces, of the carriage
were a caliber in thickness, so the bigger the gun, the more massive
the mount.

A 24-pounder cheek would be made of timber about 6 inches thick. The
Spaniards often used mahogany. At Jamestown, in the early 1600's,
Capt. John Smith reported the mounting of seven "great pieces of
ordnance upon new carriages of cedar," and the French colonials also
used this material. British specifications in the mid-eighteenth
century called for cheeks and transoms of dry elm, which was very
pliable and not likely to split; but some carriages were made of young
oak, and oak was standard for United States garrison carriages until
it was replaced by wrought-iron after the Civil War.

For a four-wheeled English carriage of 1750, height of the cheek was
4-2/3 diameters of the shot, unless some change in height had to be
made to fit a gun port or embrasure. To prevent cannon from pushing
shutters open when the ship rolled in a storm, lower tier carriages
le