|1899 Apparatus for steadying guns on shipboard. US Patent 640051A|
A self leveling gun platform sounds like a really good idea. Back in the late 19th Century, gun people had gotten very good at building big guns and along with building the guns they had also developed the math needed to calculate the trajectory of the fired shot. However, those predictions depend on the gun having a solid fixed base. A ship is just the opposite of a fixed base. Even on a calm day, with a ship at anchor, there is going to be some movement, and any little movement is going to destroy the accuracy of the gun. So you can see how having a platform that sits level regardless of what kind of monkey motions the ship is making could make hitting your target a possibility instead of a lucky strike.
WW2 battleships had ginormous electro-mechanical computers for aiming their guns. I've looked into those before, but what I didn't realize is that these systems incorporated gyroscopes. I mean, why would you need a gyroscope? A battleship is so big and heavy, it's not going to move, it's like a floating rock. Except it's not. Everything that floats is subject to the motion of the water. Never mind all those scenes of battleships cruising sedately across an ocean that looks flat as a mill pond.
Eventually I stumbled on this article by Gene Slover and I realized that all of guns on a battleship were mounted on self leveling platforms. The platforms didn't contain gyroscopes, but relied on electrical signals sent via wires from the master gun control computer. The signals caused motors to run or hydraulic valves to open to do the actual work necessary to keep the platform level. So on a ship that is engaged in a battle, all of the gun platforms are all tilting in unison to compensate for the motion of the ship.