A steam pinnace (length 26 feet, beam 5 feet 4 inches, depth 2 feet 5 inches; trial speed 7 to 8 miles per hour) built by Messrs. Forrest and Sons, for Messrs. Kohn Penn and Son, Engineers, Greenwich, was fitted with a single cylinder four and a quarter inch by five inch stroke inverted vertical marine engine operating at 360 revolutions per minute on steam supplied at 100 pounds per square inch vertical boiler, constructed and fitted by Messrs. Penn themselves, driving a three bladed propeller 2 feet in diameter with a pitch of 2 feet 6 inches.