The Harrisburg had two decks, properly so called,--the spar-deck and the berth-deck. On the former, where the guns were placed, all the working of the ship is done, as well as the fighting. There is no house or other structure upon it, as is generally seen on board a merchant-ship. Upon the berth-deck the men eat and sleep. The after-part of this deck contains the cabins of the officers. The captain occupies a cabin by himself in the aftermost part of the ship. Next forward of this is a large apartment, having small staterooms on each side of it, called the wardroom, which belongs to the commissioned officers of the ship. Next to the wardroom is an apartment called the steerage, divided into two parts, the port and starboard steerage, in which live the midshipmen and master’s mates, the assistant-engineers in a steamer, and the “forward officers,”--viz., the boatswain, gunner, carpenter, and sailmaker. Down in the bottom of the ship are placed the boilers and engines. The hold, or place under the berth-deck, is divided into a great number of rooms; such as the paintroom, the storeroom, the breadroom, shot-locker, shellroom, sloproom, magazine, lightroom, coal-bunkers, chain-lockers, tier-gratings, and other cells and holes. The magazine contains the powder, and is lined with copper. It is so constructed that it can be filled with water--flooding the magazine--when the ship takes fire. No man is allowed to enter it unless clothed in a dress prescribed for this duty, with no nails in his shoes, or metal buttons upon his garments. The lightroom adjoins the magazine, and is simply a small room to hold the powerful reflecting lamp, which throws its light into the magazine through a large pane of heavy glass. This arrangement is intended to prevent the necessity of taking a lantern into the magazine, where the slightest spark might doom the noble ship to instant destruction, and her gallant crew to an untimely death. The principal officer of the Harrisburg was the captain, whose rank in the navy, at the time of which we write, was that of commander. Under the old system, the highest grade in the navy was captain, who, when he commanded a squadron (two or more vessels) was called a commodore; but this title was not authoritatively recognized in the Navy Department. A captain who had been in command of a fleet or squadron was thereafter called “commodore,” as a mark of distinction, in the same manner that a member of Congress keeps his “Hon.” after he has ceased to hold his office.