The harbor contains the shipping of all civilized nations, and the flags of some of the barbaric powers are often to be seen at our piers. The North River piers are devoted to the great ocean steamship lines, and the steamers to domestic ports, while the East River is occupied by the old sail-vessels almost entirely. Each river has its peculiar characteristics, so that in leaving the water on one side of the island, and passing over to it again on the other side, one might easily imagine himself in a different port from that he has just left. The harbor is always full of vessels, and sometimes as many as fifteen first-class steamships will sail from the bay in a single day, bound for foreign and domestic ports. This is exclusive of the large number of river and sound steamboats, and sail-vessels, that arrive and depart daily. THE HARBOR POLICE. The peace and safety of the harbor are watched over by a police force, whose head-quarters are on a steamer. The force is composed of resolute and daring men, as the persons they have to deal with are mostly hardened characters, reckless sailors and the like. There are twenty- five men in the whole force, under the orders of a Captain and two Sergeants. They have charge of the two rivers and the upper and lower bay, and are constantly moving to and fro in their steamer and row- boats. The headquarters steamer is a gloomy looking black craft, called the "Metropolitan," which may be seen at all hours of the day and night moving swiftly around the city. The harbor police render efficient service during fires in the shipping, and are often called upon to suppress crime and violence, which are attempted beyond the reach of the patrolmen on shore. THE RESCUE STATIONS.