e other end of the beams serves to connect them together and to the
connecting rod which, proceeding from thence upwards, engages the crank,
and thereby turns round the paddle wheels.

115. _Q._--Will you further illustrate this general description by an
example?

[Illustration: Fig. 26.]

_Q._--Fig. 26 is a side elevation of a side lever engine; x x represent the
beams or keelsons to which the engines are attached, and on which the
boilers rest. The engines are tied down by strong bolts passing through the
bottom of the vessel, but the boiler keeps its position by its weight
alone. The condenser and air pump are worked off the side levers by means
of side rods and a cross head. A strong gudgeon, called the _main centre_,
passes through the condenser at K, the projecting ends of which serve to
support the side levers or beams. L is the piston rod, which, by means of
the cross head and side rods, is connected to the side levers or beams, one
of which is shown at H H. The line M represents the connecting rod, to
which motion is imparted by the beams, through the medium of the cross tail
extending between the beams, and which by means of the crank turns the
paddle shaft S. The eccentric which works the slide valve is placed upon
the paddle shaft. It consists of a disc of metal encircled by a hoop, to
which a rod is attached, and the disc is perforated with a hole for the
shaft, not in the centre, but near one edge. When, therefore, the shaft
revolves, carrying the eccentric with it, the rod attached to the
encircling hoop receives a reciprocating motion, just as it would do if
attached to a crank in the shaft.

116. _Q._--Will you describe the mode of starting the engine?

_A._--I may first mention that when the engine is at rest, the connection
between the eccentric and the slide valve is broken, by lifting the end of
the eccentric rod out of a notch which engages a pin on the valve shaft,
and the valve is at such times free to be moved by hand by a bar of iron,
applied to a proper part of the valve gear for that purpose. This being so,
the engineer, when he wishes to start the engine, first opens a small valve
called the _blow through valve_, which permits steam from the boiler to
enter the engine both above and below the piston, and also to fill the
condenser and air pump. This steam expels the air from the interior of the
engine, and also any water which may have accumulated there; and when this
has been done, the