As I mentioned earlier, the cannons of the CSS Pee Dee could provide insight into the "beginning of modern naval warfare." The three cannons were each mounted on the ship so as to be able to provide for a 360 degree arc of fire as they were on swivels. Before, and during the war, ships most often relied on guns mounted along the sides of the warships.
So, a ship listed as carrying 38 cannons, would only be able to bring 19 of them to bear on an enemy ship during a battle at a single point.
Modern warships mounted cannons in an armored turret which swiveled. The Pee Dee, however, had them mounted in the open.
Also of interest is that one of the cannons was originally on a Union ship.