tial plan view. Fig. 5 is a detail view of the upper
end of the connecting rod and its connections; and Fig. 6 is a
horizontal section taken through the middle of the valve chamber.

The cylinder, A, is threaded externally for 1 inch from its lower
end, and the collar, a, 1/4 inch thick, is screwed on and soldered.
The face of the collar is afterward turned true. The same thread
answers for the nut which clamps the cylinder in the plate, B, and
for the gland, b, of the stuffing box, which screws over the beveled
end of the cylinder, and contains fibrous packing filled with
asbestos or graphite. The posts, C, are shouldered at the ends and
secured in their places by nuts. Their bearing surface on the plate,
D, is increased by the addition of a collar screwed on. The posts
are made from drawn rods of brass, and need no turning except at the
ends.

[Illustration: Fig. 1.--SIMPLE SINGLE-ACTING STEAM ENGINE]

The cylinder head, E, which is a casting containing the valve
chamber, is screwed in. The piston, F, fits the cylinder closely,
but not necessarily steam tight. The head is screwed in and
soldered, and the yoke, G, which receives the connecting rod pin, is
screwed into the head. The connecting rod, H, is of steel with brass
ends. The lower end, which receives the crank pin, is split, and
provided with a tangent screw for taking up wear. The crank pin is
secured in the crank disk, I, by a nut on the back. The eccentric
rod, J, is of steel, screwed at its lower end into an eccentric
strap of cast or wrought iron, which surrounds the eccentric, K. The
valve, L, is slotted in the back to receive the valve spindle, by
which it is oscillated. The ports are formed by drilling from the
outside, and afterward forming the slot, with a graver or small
sharp chisel. The supply port, for convenience, may be somewhat
enlarged below. The holes for the exhaust port will be drilled
through the hole into which the exhaust pipe is screwed. The chamber
communicating with the exhaust is cored out in the casting.

The easiest way to make the valve is to cut it out of a solid
cylinder turned to fit the valve chamber.

An engine of this kind will work well under a steam pressure of 50
lb., and it may be run at the rate of 200 to 250 revolutions per
minute.

[Illustration: SIDE ELEVATION. SECTIONAL, AND DETAIL VIEWS OF
SIMPLE STEAM ENGINE]

It is desirable to construct a flat pasteboard model to verify
measurements and to get the prop