In another great particular did the Poughkeepsie differ from the corvette-built vessels that were so much in favor at the beginning of the century; a species of craft obtained from the French, who have taught the world so much in connection with naval science, and who, after building some of the best vessels that ever floated, have failed in knowing how to handle them, though not always in that. The Poughkeepsie, while she had no spar, or upper deck, properly speaking, had a poop and a top-gallant-forecastle. Within the last were the cabins and other accommodations of the captain; an arrangement that was necessary for a craft of her construction, that carried so many officers, and so large a crew. Without it, sufficient space would not be had for the uses of the last. One gun of a side was in the main cabin, there being a very neat and amply spacious after cabin between the state-rooms, as is ordinarily the case in all vessels from the size of frigates up to that of three-deckers. It may be well to explain here, while on this subject of construction, that in naval parlance, a ship is called a single-decked vessel; a _two_-decker or a _three_-decker, not from the number of decks she actually possesses, but from the number of _gun_-decks that she has, or of those that are _fully_ armed. Thus a frigate has four decks, the spar, gun, berth, and orlop (or haul-up) decks; but she is called a “single-decked ship,” from the circumstance that only one of these four decks has a complete range of batteries. The two-decker has two of these fully armed decks, and the three-deckers three; though, in fact, the two-decker has five, and the three-decker six decks. Asking pardon for this little digression, which we trust will be found useful to a portion of our readers, we return to the narrative. Harry conducted Rose to the poop of the Poughkeepsie, where she might enjoy the best view of the operation of getting so large a craft under way, man-of-war fashion. The details were mysteries, of course, and Rose knew no more of the process by which the chain was brought to the capstan, by the intervention of what is called a messenger, than if she had not been present. She saw two hundred men distributed about the vessel, some at the capstan, some on the forecastle, some in the tops, and others in the waist, and she heard the order to “heave round.” Then the shrill fife commenced the lively air of “the girl I left behind me,” rather more from a habit in the fifer, than from any great regrets for the girls left at the Dry Tortugas, as was betrayed to Mulford by the smiles of the officers, and the glances they cast at Rose. As for the latter, she knew nothing of the air, and was quite unconscious of the sort of parody that the gentlemen of the quarter-deck fancied it conveyed on her own situation.