should be 1-1/2 inches in diameter, while the bent crank
has a throw of 3/16 inch. The steam-cylinder is fixed on the outside of
one of the uprights, and the steam-pipe must, of course, be fitted from
the inside.

The pump-cylinder is composed of a small piece of brass tube 1 inch long
and 3/8 inch in diameter. The plunger is 1/2 inch long, and the diameter
is just sufficient to enable it to work freely up and down inside the
brass tube. One end is shaped as shown in Fig. 125. This contains a saw
cut that enables the pump-rod to be placed between and connected with a
pin. The bottom end of the cylinder is now fitted with a brass disk in
which a hole is made and a 3/32-inch tube soldered in place. The inside
surface of this piece of brass should be countersunk, and the piece is
then soldered into the end of the cylinder. Before the plunger is
inserted a small lead shot is dropped in, which should be larger than
the hole at the bottom of the cylinder, thereby covering it. A hole is
drilled in at the side of the cylinder, and a small bent pipe fixed in
it. At the top of this pipe a short piece of 3/8-inch brass tube is
fixed in place, as indicated. This piece of tubing is closed at both
ends. The bottom end is treated like that of the pump-barrel and
supplied with a large shot. An outlet-pipe is soldered into the side of
the delivery-valve chamber and leads to the side of the hull.

The pump _E_ is fixed at the bottom midway between the engine uprights
as indicated in Fig. 124. The suction-pipe passes through a hole and
down through the deck nearly to the bottom of the hull. After the
engine and boiler are connected, a trial can be made. If the foregoing
instructions have been carried out, the engine will run at a good speed
and a continuous flow of water will be pumped out of the hull. All parts
of the engine and pump should be carefully oiled and water should be
poured into the pump in order to prime it before its start.

It is understood that two complete boilers and pump units are made for
the model, and one is mounted on each side. If the builder desires to
increase the capacity of the pumps and install a more powerful boiler
and engine, only one pump will be necessary. Otherwise the water will
not be pumped from the hull very rapidly.

When the builder has finished the pump units, he should turn his
attention to the remainder of the fittings. Two small cranes are made,
and one is placed at each side of the hull. T