On board a man-of-war, everything is arranged with the nicest precision. A thorough system pervades the ship, and everything is done by rule. The Harrisburg had a hundred and twenty men crowded upon her spar-deck at this muster: but in a short time, under the efficient and methodical arrangement of Mr. Bankhead, order came out of chaos; and, when he had finished his work, every man knew where he belonged during each hour of the day and night; where he was to go when the ship went into action; when she was to tack or wear; when the sails were to be set, furled, or reefed; where he was to take position if the ship caught fire, or was boarded by an enemy. Every one knew where he was to eat and sleep, where he was to stow his hammock and clothes-bag, and everything else which was to enable him to discharge his duty as one of the wheels in the complicated machine of which he was an essential part. If our readers are not familiar with ships, we shall find it very difficult to make them comprehend Jack Somers’s position and duties on board the Harrisburg; but we shall endeavor to give them some ideas upon the subject. A ship, and especially a man-of-war, is a complicated structure; and our young friends must not expect any more than a partial view in these pages, for the whole volume would be no more than sufficient to do justice to the subject.[A] The Harrisburg was a screw-steamer of about two thousand tons burden, and usually denominated a sloop-of-war. She was a full-rigged ship; that is, she had square sails on her fore, main, and mizzen mast, and could be worked under sail or steam, as occasion or necessity might require. She carried twenty-eight guns, all of which were placed upon her upper or spar deck. Some large men-of-war, called ships-of-the-line, have four decks. The Ohio, in which Jack had spent several weeks, was of this class. The upper deck is then called the spar-deck; the next below it, the gun-deck; the third, the berth-deck; and the fourth, or lowest one, the orlop-deck. The decks, which in a house would be called floors or stories, are not divided off into rooms; so that, forward of the officers’ cabins, they look like long halls. The square holes, or windows, through which the muzzles of the cannon are pointed, are called port-holes, or ports. They are closed by two doors,--one swinging up, and the other down.