strength and safety." Overall, the hull was deemed to provide "adequate stability, ease of motion, and every other good sea quality." This assessment would be borne out in practice: Commonwealths longstanding captain, Jerome W. Williams, would later describe the vessel as "the finest boat for rough water ever built" in the United States. Machinery Commonwealth was powered by a 1,200 horsepower, 19 rpm single cylinder vertical beam steam engine, with 76-inch bore, 12-foot stroke and Stevens cut-off set at 7 feet, built by the Morgan Iron Works of New York. The engine was fitted with a safety device, designed by Erastus W. Smith, which uncoupled the eccentric in the event of the piston moving further than its prescribed limit, to prevent further damage in the event of a component failure. Steam, at an average pressure of 30 psi (max. 40) was supplied by a pair of 38-foot by 13-foot-6-inch cylindrical iron return-flue boilers, placed on the guards forward of the paddlewheels. The boiler furnaces, six in total, were fitted with blower engines and used anthracite coal for fuel, about 30 tons of which could be stored in the ship's coal bunkers. The paddlewheels were 38 feet in diameter and each fitted with 28 10-foot 6-inch paddles, with a dip of 32 inches—40 inches when the vessel was fully loaded. While Commonwealths speed is not recorded, it is said to have been unexceptional. Passenger accommodations Commonwealth was noted for the excellence of her passenger accommodations, designed by architect Alexander Hawkins. One feature in particular—the domed upper roof—drew praise, including that of a correspondent for The New York Times: thumb | upright | Detail of Commonwealths upper saloon, showing the domed roof. This stereoscope, taken c. 1860 by George Stacy, is one of the earliest photos of the interior of an American steamboat. One of the most noticeable and praiseworthy [features] ... is a semicircular roof to the upper saloon, which gives an air of spaciousness, elegance and comfort that is as novel as it is cheering. This arched roof extends nearly the entire length of the boat, and the prospect through the long corridor is enchantingly beautiful; the arched roof sits so gracefully on its supports, and its ribs are so light, that it seems self-sustained, like the blue arch above our heads. It is painted with exquisite taste a pure white, for any attempt at ornamentation would mar its graceful