Data from trials of the steam launch Firefly (length, 53 ft.; beam, 6 ft. 6 in.; draught, 2 ft. 6 in.; mean speed, 19 miles per hour)) fitted with a two cylinder 6 in, diameter by 8 in. stroke inverted vertical direct-acting marine engine, built for Mr. Henry Morrel, of the Société de la Lys, of Ghent, by John I. Thornycroft and Co., of Chiswick and an unnamed steam launch (length 57 ft.; beam 7 ft. 2 in.; draught, 2 ft. 5 in.; mean speed 17 miles per hour).