of which is to
collect the water in a narrow band, instead of spreading it over a large
surface. This materially assists in its escape, and at the same time
presents a large surface for the distribution of any water that may not
find its way out in advance of the piston.

The piston is a single casting unusually long and light, and is packed
with four spring rings of 3/8 inch square brass wire.

The valve is a simple rectangular plate, working between the valve face
and a cover plate, the cover plate being held in its proper position,
relative to the back of the valve, by steam pressure against its outer
surface, and by resting against loose distance pieces between its inner
surface and the valve seat. This construction admits of the valve
leaving the seat, if necessary, to relieve the cylinder from water, as
in the instance of priming, and also, by the reduction of these pieces,
admits of ready adjustment to contact, should it become necessary.

[Illustration: Fig. 311--VALVE MOTION.]

The cover plate is provided with recesses on its inner surface which
exactly correspond with the ports in the valve face, and the
corresponding ports and recesses are kept in communication with each
other by means of relief passages in the valve. From this it will be
seen that the valve is subjected to equal and balanced pressure on each
of its sides, and hence, is in equilibrium.

The valve is operated through the valve motion, shown in Figure 311, the
eccentric rod of which hooks on a slightly tapered block that turns on
the pin of the rock arm, like an ordinary journal box.

The expansion, or cut-off, is automatically regulated by the operation
of the governor in swinging the slotted eccentric in a manner
substantially equivalent to moving it across the shaft, but is however
favorably modified by the arrangement of the rock arm, which, in
combination with the other motions, neutralizes the unfavorable
operation of the usual shifting eccentric, and which, in connection with
the large double port opening, provides for a good use of steam from 0
to 3/4 stroke.

The governor shown in Figure 312 is of the disc and single ball type,
the centrifugal force of the ball being counteracted by a powerful
spring. Friction is reduced to a minimum in the governor connection, by
introducing steel rollers and hardened steel plates in such a manner as
to provide rolling instead of sliding motion.

In order that a governor shall correctly perfo