Monitor warship typeThe USS Monitor became the prototype of a form of ship built by several navies for coastal defence in the 1860s and 1870s and known as a monitor. It was a low freeboard, mastless steam-powered vessel with one or two rotating armoured turrets. The low freeboard meant that these ships were unsuitable for ocean-going duties, but had the advantage that there was less area to cover with armour and the sea washing over the deck in heavy weather would keep the vessel stable.
A more seaworthy variation was called the breastwork monitor, and had the turrets and any superstructure mounted on a raised platform. These were not particularly successful as sea-going ships, because of the short range caused by the low efficiency and poor reliability of the steam engines of the day. The first of these ships was the HMVS Cerberus, built in 1868 to 1870 and which still exists (in rather poor condition) near Melbourne, Australia.
Attempts were made to design variations of these ships which were fully rigged to overcome both the technical and the cultural problems of relying upon a steam engine (naval tradition in the larger navies of the time meant that steam power was looked down upon).
These were mostly unsuccessful because the rigging interferred with the turrets' 360 degree arc of fire and because of problems with the ships' stability caused by the combined weight of turrets and masts above the waterline. However, the monitor did eventually evolve into the battleship.
The monitor as a class of warship reappeared in a rather different form during the First World War as a flat bottomed sea-going barge equipped with battleship-sized guns and intended for bombardment of the enemy coast. Several of these ships were still in existence, and a few more were built, to play a part in the Second World War.