and plays back and forth in the barrel. The vertical check valve is
placed between the pump and the water supply. It is not absolutely
necessary that the first check be a vertical one, but a check of some
kind must be so placed. As the water is lifted up to the boiler it is
more convenient to use a vertical check at this point. Just ahead and a
few inches from the pump barrel is a horizontal check valve. Following
the course of the water toward the point where it enters the boiler, you
will find another check valve. This is called a "hot water check." just
below this check, or between it and where the water enters the boiler,
you will find a stop cock or it may be a globe valve. They both answer
the same purpose. I will tell you further on why a stop cock is
preferable to a globe valve. While the cross head pumps may differ as
to location and arrangement, you will find that they all require the
parts described and that the checks are so placed that they bear the
same relation to each other. No fewer parts can be used in a pump
required to lift water and force it against steam pressure. More check
valves may be used, but it would not do to use less. Each has its work
to do, and the failure of one defeats all the others. The pump barrel
is a hollow cylinder, the chamber being large enough to admit the
plunger which varies in size from 5/8 of an inch to I inch in diameter,
depending upon the size of the boiler to be supplied. The barrel is
usually a few inches longer than the stroke of the engine, and is
provided at the cross head end with a stuffing box and nut. At the
discharge end it is tapped out to admit of piping to conduct water from
the pump. At the same end and at the extreme end of the travel of the
plunger it is tapped for a second pipe through which the water from the
supply reaches the pump barrel. The plunger is usually made of steel and
turned down to fit snug in the chamber, and is long enough to play the
full stroke of engine between the stuffing box and point of supply and
to connect with the driver on the cross head. Now, we will take it for