ther circumstances, provided the fire is low enough to require fuel,
the best time to put on coke is when the water is sufficiently high to
turn off the feed-pumps, the steam slightly blowing off, and the Engine
travelling at a good speed.

No definite instructions can be given for the frequency with which coke
must be laid on the fire, as it varies according to the duty to be done,
and the water consequently to be evaporated: in cases of heavy duty and
bad gradients, it may at times be necessary even at as short an interval
as 2 miles; under contrary circumstances an Engine may sometimes run as
much as 15 miles without adding fresh coke.

The fire should be allowed to run rather low before arriving at the top
of an inclined plane down which the steam will not be used: on beginning
to descend the plane, fuel should be put on the fire, which will burn up
by the time the train reaches the bottom of the plane.

If it is wished to keep up the steam, it is better not to supply water
and fuel at the same time.

While running, the Stoker should occasionally pick the ashes from the
tubes to clear the draught.

By observing the above rules for the supply of water and coke, an
efficient pressure and quantity of steam will be produced, which it must
be the study of the Engine-man to economise. With this view the
regulator should never be kept too far open;--as soon as the train has
acquired the velocity wished, the aperture may be considerably reduced
without diminishing the speed. As any diminution in the amount of steam
used causes a corresponding diminution in the quantity of coke consumed,
the skill of the Engine-man should be unceasingly directed to the
reduction of so heavy an item of Railway expenditure.

If there should be, at any time, an unnecessary quantity and force of
steam, it is readily reduced by opening the fire-door, and by turning on
the feed-pumps; if there should be too little, the Engine-man must be
content to run slowly for a short time, keep the regulator only partially
open, and put on a gradual supply of coke.

When the water in the boiler is high, many Engines begin to prime,
especially after running for several days. When this occurs, the
aperture of the regulator should be diminished, and the fire-door and the
discharge cocks of the cylinders opened: if the height of the water will
allow it, the blow-off cock of the boiler may be opened for a short time
to carry off the sediment, which will b