The boilers of these engines are fitted with superheaters, making them more efficient, and in place of a lever-type regulator they have a wheel that must be turned times between closed and fully open. The drive from the cylinders and to the wheels again uses levers, but in a different pattern. The linkage is fitted within double frames at the front of the locomotive. This results in a locomotive that is far more rigid. The side tanks are arranged vertically just in front of the cab. No. 6 carries the same amount of water as the earlier engines, but Nos. 7 and 8 carry enough water to get to the top of the mountain without stopping, if required. There is no separate tank for cooling water as it is drawn from the boiler on these engines.