The _Marion_ class of sloops, launched about the same period, are of an increased displacement and speed, and built of wood. The length of the _Marion_ is 216 feet, beam 37 feet, draught of water 16.6 feet. She has a displacement of 1900 tons, and attains a speed of 12.9 knots per hour with an indicated horse-power of 966. The capacity of her coal-bunkers is 135 tons. Her battery consists of one 8-inch muzzle-loading rifle (converted), six 9-inch smooth-bores, and one 60-pounder. [Illustration: U. S. SLOOP-OF-WAR “ALERT” (IRON).] The _Alert_ is one of three vessels that were built of iron in 1874, the exceptional and spasmodic indication of an effort to change the material for construction, much induced by pressure from the iron interests of the country. This effort was made in a very mild and tentative manner, and was limited to this small class of diminutive vessels. The length of the _Alert_ is 175 feet, beam 32 feet, draught of water 12.9 feet. She has a displacement of 1020 tons, and attains a speed of ten knots per hour with an indicated horse-power of 655. The capacity of her coal-bunkers is 133 tons. Her battery consists of one 11-inch and four 9-inch smooth-bores, and one 60-pounder. [Illustration: U. S. SLOOP-OF-WAR “TRENTON.”] The shock attending the first step towards a change in the material for construction was so great as to cause a suspension of the effort, and in 1876 was launched the _Trenton_, built of wood, which represents the latest of that type on the list of the navy. The length of this ship is 253 feet, beam 48 feet, draught of water 20.6 feet. She has a displacement of 3900 tons, and attains a speed of 12.8 knots per hour with an indicated horse-power of 2813. The capacity of her coal-bunkers is 350 tons. Her battery consists of ten 8-inch muzzle-loading rifles (converted). The above is a fair presentation of our old navy. Of such vessels we have, larger and smaller, twenty-five which are fit for service as cruisers, exclusive of the old single-turreted Monitors. These cruisers are built of wood, have low speed, and are armed with smooth-bore guns, with a sprinkling of rifled cannon, converted on the Palliser system from smooth-bore cast-iron guns. Of what service is this force, this relic of a past age? The duties of a navy, apart from the consideration of war, are manifold. As stated by the first Advisory Board, it is required for “surveying, deep-sea sounding, the advancement and protection of American commerce, exploration, the protection of American life and property endangered by wars between foreign countries, and service in support of American policy in matters where foreign governments are concerned.”