=The Marsh Steam Pump= is so constructed that the exhaust steam may
be turned into the suction, thereby condensing its exhaust steam and
returning it with its heat to the boiler, thus heating the feed water
to a high degree.
The pump is automatically regulated and can never run too fast to take
suction, or should the water supply give out when the throttle valve is
wide open no injury can occur to the moving parts.
The steam valve, though nicely fitted, moves freely in the central bore
of the steam chest, and has no mechanical connection with other moving
parts of the pump, but is actuated to admit, cut off and release the
steam by live steam currents which alternate with the reciprocation of
the piston.
Each end of the valve is made to fit the enlarged bore of the steam
chest, and it is due to these large valve heads, which present
differential areas to the action of steam and the perfect freedom of
the valve to move without hindrance from other mechanical arrangements
or parts, that the flow of steam into the pump is automatically
regulated.
[Illustration: MARSH PUMP.