 HMS "Temeraire" was completed in 1877 with two disappearing guns (muzzle-loading rifles on Moncrieff-type carriages) sinking down into barbette structures (basically circular metal protective walls over which the gun fired when elevated).This was to combine the ability of the early pivot guns to swivel with the protection of more classical fixed naval guns.A similar design was later used in Russia for the first ship of the "Ekaterina II"-class battleships and also used in the monitor "Vitse-admiral Popov".