This is the Winans Steam Gun it used steam to fire projectiles rather than gunpowder. The sheilded barrel rotated 250 times per minute and fired a projectile at the end of each rotation. Its creators William Joslin, and Charles S. Dickinson they couldn't grasp the fact that they couldnt make it fire farther and with more killing power than a gunpowder weapon.
This weapon was called a Coal "Torpedo"( Back then a torpedo was bascically any thing that was intended to explode) the whole point of this to place in a pile of confederate coal so when they put it in a fire it exploded rendering the ship or train useless