low:
indeed the Engine-man should manage that it may never be necessary in the
latter case, as the addition of water rapidly lowers the steam.

In order to know the force of the steam, one hand may occasionally lift
or depress for a moment the lever of the safety-valve, according as the
steam is under or over the working pressure; and a little practice will
soon enable a person to judge the extent of excess or deficiency.

Both feed-pumps should not commence working at the same time.

The water should never be allowed to run low before arriving at any part
of the road where considerable power is required, as steam is produced
more rapidly when both pumps are turned off,--a measure which is
imprudent unless the water is high.

When "the feed" is turned on, the Engine-man should try the pet-cock to
see whether the pump is acting freely: the water thrown from it should be
in forcible intermittent jets; warm water with a little steam will
frequently escape from it at first; if this should continue, it may be
concluded that the upper clack does not act; and if the water is in a
continuous stream without pulsations, the lower clack is out of order.
In either case it will not be prudent to trust too much to the faulty
pump, but the evil may frequently be remedied by working the pump a short
time with the pet-cock open, or alternately turned on and off.

Coke is put on the fire by the Stoker, at the order of the Engine-man,
who should hold the chain of the fire-door in his hand, and open it for
as short a time as possible, while the Stoker throws on each shovelful of
coke: the shovel should be well filled, and the coke distributed equally
over the fire.

In most Engines, the fuel need not be higher than the bottom of the
fire-door; and if allowed to fall more than 6 or 8 inches below it, it
must not be expected that the pressure of the steam will be maintained,
if the Engine has a load.

The supply of fuel should be regular, and so arranged that the fire may
have burned up well by the time the steam is most required. As the
addition of fuel causes a temporary reduction of the force of the fire,
coke should not be laid on immediately before arriving at an inclined
plane or any part of the road where much power is required; but when
ascending an incline, coke should be gradually added when the Engine
begins to _beat heavily_,--the draught is then powerful, and a regular
supply of fuel required to keep up the fire.

In o