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 other 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.