From a drawing prepared for the Patent Specification; shows the adoption of the Long Boiler with the final abandonment of the outside frame; the steam chest placed between the cylinders and the forked gabs combined on the valve spindle; other features are the marine type of connecting rod big end, and the regulator in the smokebox above the steam chest. Description from A Century of Locomotive Building by Robert Stephenson & Co 1823-1923, J G H Warren, p 349. Drawing reference - 90.