the concept of a revolving gun turret was not novel to armed forces of the
mid-19th century, the USS Monitor was the first vessel in history to
incorporate this engineering feature. The revolving gun turret allowed the
ship's crew to aim cannons without having to position the ship to deliver a
The Monitor's gun turret consisted of an iron skeleton covered with
eight layers of one-inch-thick plates. Only 20 feet in diameter on the inside,
the turret was a claustrophobic place in combat. Inside were two 11-inch
Dahlgren smoothbore cannons, which were mounted on specially designed "friction
carriages" and operated around and under the skeletal frame. On recoil, the
cannons cleared the diagonal braces with only about two inches to spare. After
workers assembled the turret, they drilled three 20-inch-diameter holes through
the armor, one atop the other, to make each gun port.
Thick iron pendulums (or port stoppers) that hung from the overhead protected
the gun-port openings. Crew swung the port stoppers out of the way when they
ran the cannon out for firing and dropped them back into place on recoil to
protect themselves from enemy fire. The Monitor's cannons were muzzle
loaders, meaning that powder and shot were loaded into the cannon from the
business end. Because of the confined space inside, each port stopper had a
hole through its center to allow the handles of the gun tools to pass through.
During loading, the handles protruded outside the turret; when not in use, the
loading implements hung from the overhead.
Crew members stored a limited number of non-exploding solid shot along the base
of the turret beside each of the guns. As the turret slowly revolved, crew
would pass powder and exploding shells up from below. The turret floor had four
hatches (two beside each gun) for access down to the berth deck.
The turret was controlled by linkage at the rear of the starboard gun. Below
deck, two donkey engines (small auxiliary engines) connected to a crank—which, in turn, was connected
to four gears—put the turret in motion. Its maximum speed was two
revolutions per minute.
Before the turret could be revolved, it had to be "keyed up." On the forward
side of the midships bulkhead was a Y-shaped structure called the turret
support truss. This large mount helped displace the weight of the turret
resting on the deck above. In the center of the truss stood the turret shaft,
which crew raised into position by pulling a large wedge underneath. As they
tightened a large nut on the end of the wedge, the shaft slowly rose up to
connect with the yoke on the main beam at the bottom of the turret. Once the
shaft was in place, crew members turned the control wheel in the turret, which
increased the steam pressure to the donkey engines and put the turret in