The _Passaic_ was built of iron, and was launched in 1862. Her length is 200 feet, beam 46 feet, draught of water 11.6 feet. She has a displacement of 1875 tons, and attains a speed of seven knots per hour with an indicated horse-power of 377. The capacity of her coal-bunkers is 140 tons. Her battery consists of one 15-inch smooth-bore and one 11-inch smooth-bore. Her sides are protected by five inches of laminated iron, and her turret by eleven inches of the same. This vessel and eleven others of her class constitute the entire armored fleet of the United States. Too much credit cannot be awarded to Captain Ericsson for his brilliant conception of this floating battery, and the navy must be ever grateful to him for preserving it from the dire disaster which was averted by the appearance of the original _Monitor_ at the moment of a great crisis. These vessels bore themselves well through the storms of elements and battle during the war, proving capable of making sea-voyages, and of resisting the effects of the artillery that was in use during the period of their usefulness; but an interval of more than twenty years has produced such a change in artillery as to make the protection afforded by a few laminated plates of one-inch iron but a poor defence against weapons which have robbed this fleet of its once formidable character. Although many of the features of the original design may be retained in new constructions, most of the details will be changed, notably in the turret, in consequence of the greater weight resulting from the increased thickness of armor. The central spindle around which the Ericsson turret revolves must disappear, and the turret must turn on rollers under the base.