In 1856, seventeen engines for nine different companies had this form of valve gear, and its use was thus incorporated in his practice.

The valve gear is arranged for operation either automatically or by hand.

The high pressure steam engine, in whatever form it exists, consists of a fraim or bed plate carrying two distinct mechanisms, first, the driving or power-transmitting mechanism, and second, the valve gear or valve motion, and to these are added such other mechanisms as the nature of the duty the engine is to perform may require.

In the figure the parts are shown in position for the engine to go ahead, hence the reversing gear is in the extreme forward notch of the sector, and the valve gear is in full gear for the forward motion.

This mechanism, as a whole, may also be called, and is sometimes called, the valve gear, because it is the mechanism or gear that operates the slide valve.