A steam launch (length 37 feet, beam 6 feet 6 inches, draught 2 feet 6 inches; trial speed 9 miles per hour) was fitted with a four and a half inch by four and a half inch stroke twin cylinder 20 horsepower inverted-vertical simple marine engine; built by Messrs. Yarrow and Hedley, Poplar. Each of the cylinders with its respective frame was cast in one piece, the guide were bored out with the same tool as the cylinders and the piston rods with sliding blocks attached were turned up together insuring a perfectly true job.