On October 17, 1870 David Dixon Porter became Chief of the Bureau of
Navigation of the U.S. Navy. He brought with him a highly controversial vision
for the Navy’s future. Most officers and politicians had succumbed to “Monitor
fever” when the plucky little turret ship had appeared on the stage eight years
before, and few ships of other types had been built since the end of the Civil
War. But Porter knew the turret ships could not answer every challenge the Navy
faced. They were expensive and slow to build. Their low freeboards made them
notoriously poor sea-boats. Most of all, they were as vulnerable as the next
ship to spar torpedoes. This invention had deeply impressed Admiral Porter
during the Civil War, and he was determined to develop it to its full potential,
and against the opposition of the Monitor lobby.
A spar torpedo consists of a bomb on a long pole or spar, carried by a small, fast, low-lying boat. Under the cover of night or fog the torpedo boat stealthily approaches an enemy ship and detonates the bomb close to the vulnerable underwater hull. This may sound simple enough in theory, but experience had shown these missions to be suicidal under the best of circumstances. Once detected, the little torpedo boats were highly vulnerable, and even if the torpedo was deployed correctly, its charge was often too small to cause any significant damage. Spar torpedo boats were, in the eyes of one observer, little more than “a waste of good men.” Porter argued that modern technology and improved design could improve the weapon’s reliability and deadliness and make its deployment less dangerous. He envisioned a fleet of lightly armored, agile boats designed with double-hulls and watertight compartments to keep them afloat even when severely damaged; with sophisticated electrical mechanisms to deploy and trigger the torpedo, and employing telegraphy for shipboard communications. His design included a 15” Dahlgren gun, the heaviest available at the time, in a fixed mount on the bow. A 24 foot long ram prow projected forward. It contained the steam-operated torpedo mechanism. The spar was to be deployed through a valve at the tip of the ram and would project another 30 feet forward, placing the crew well out of danger from the exploding torpedo. Additional torpedoes could be deployed through valves on each beam. Gatling guns were mounted on the rail to fend of boarders. To make his vessel as stealthy as possible, Porter designed the double hull to be flooded until the spar deck was almost level with the water surface. The smoke stack would telescope to half its height, and all deck structures were to be as low as possible. Armor was to be light, and concentrated at the bow, for the ship was to fight bows-on only. The vessel would approach her enemy by stealth, open up with her massive gun, deploy her spar torpedo, and, if her victim still refused to sink, deal a fatal blow with her ram.
With this design in hand, Porter applied to Congress for funds to build one experimental vessel. Past Congresses had been famously economical when it came to naval matters, but Porter did get $250,000 for two boats. The “Intrepid” was designed by the Chief of the Bureau of Construction, Isaiah Hanscom and was built at the Charlestown Navy Yard in Boston. Porter’s brainchild took shape at the Brooklyn Navy Yard. In 1862 John Ericsson had named his turret ship “Monitor” because he wanted it to be a monitor, that is, a warning sign for the navies of the world. One can only imagine what Porter intended to communicate when he named his vessel “Alarm.”
Both ships were commissioned in 1874 and commenced trials. The “Intrepid” turned out to be a rather conventional craft that offered little innovation and was soon mothballed. The Alarm, however, was radically different from any other ship then in the U.S. Navy. She was constructed entirely of iron, the first American ship with a complete double hull built on the transverse bracket system. Electricity was used throughout the ship for lighting and communications, another first. To provide superior speed and maneuverability she had received a “Fowler Wheel”, an early cycloidal propulsion system, shaped like a four-bladed, horizontal paddle wheel. By altering the angle of attack of the blades as the wheel spun around, the pilot could change the direction of the ship instantly without using a rudder. During trials it became apparent that the Fowler wheel delivered only on the latter criterion: The Alarm spun like a top, but she was dead slow. To add to the embarrassment it was soon discovered that the engines had worked themselves loose from their bed-plates, necessitating extensive repairs to the brand-new ship. For the next four years the Alarm carried out a number of experiments at the Washington and New York Navy Yards, but mostly she lay idle. Overall the experiment was seen as a costly failure. Public opinion chided an overzealous Navy and Congress for spending freely on newfangled inventions and unproven technology.
On June 11, 1878, Lieutenant R.M.G. Brown was put in command of the Alarm, ostensibly to rescue what was left of her reputation. An enterprising and highly successful navy officer, the energetic Brown immediately launched a publicity campaign of newspaper interviews and public statements, extolling the unrealized virtues of his ship. Against a public outcry of throwing good money after bad, he successfully lobbied congress for $20,000 to replace the Fowler wheel with a better system of propulsion. By July 1881 the newly invented Mallory Steering Screw had been installed and once again the Alarm was undergoing trials in the Hudson River. Alas, the Mallory screw did almost nothing to improve her snail’s pace. In addition the 10-foot diameter of the Mallory screw had robbed the ship of her shallow draft, which had been one of her saving graces. The press had yet another field day. Undaunted, the Alarm conducted a series of experiments at the U.S. Navy Torpedo school at Newport, R.I. She eventually returned to the New York Navy Yard and was placed in ordinary. In 1891-92 she was converted to a gunnery training ship. Surviving records show she was to receive six Hotchkiss guns. However, it is not certain that these weapons were ever installed. Certainly the Alarm does not appear to have served in this new role. Continuing to deteriorate, she was struck from the Navy list in 1897. On February 23, 1898 the once formidable U.S.S. Alarm was sold for scrap