Length: 173' overall.
Beam: 28' (est.).
Displacement: 730 long tons.
Draft: 11' 1".
Propulsion machinery: coal-fired boiler; 2 x compound engines; Fowler wheel.
Speed: 7 knots design.
Battery: 1 x 15" cannon; 3 x spar torpedoes.
Designed by Isaiah Hanscom and constructed specifically for experimental work for the Bureau of Ordnance, Alarm operated from Washington, D.C. until 1877, when she moved north to the Torpedo Station at Newport, Rhode Island. She returned to Washington the following year and resumed special service.
In 1880, Alarm began a tour at New York, after which she was laid up at Norfolk, Virginia in 1883. In 1884, she returned to New York, where she was placed out of commission in 1885. In 1890 and 1891, she apparently underwent conversion to a gunnery training ship but in 1895 was listed as “in ordinary.” Her name was struck from the Navy list in 1897 and she was sold for scrapping on 23 February 1898.
Source: Bauer & Roberts.