The Engine-man should now be standing on the foot-board of the Engine, which he ought never to leave, unless the machinery is out of order, when he may leave the Stoker in his place; he should as much as possible be in such a position as to command, without moving from his place, the reversing-lever, the whistle, and the regulator, these being the parts which he is most frequently obliged to
use at the shortest notice; his hand should be upon the regulator, which, when he has arrived at a good speed, he will gradually ease off, so as to economise steam without retarding the train: his eye should be constantly directed to the rails in front of him, that he may be immediately aware of any obstruction, and at the same time his full attention must be given to the maintaining a sufficiency of steam at an equable pressure; this is to be done by using the requisite care in the manner and time of supplying water and fuel.
Water is supplied by opening the cocks in the feed-pipes, which allow the pumps to act; and the height of water in the boiler is commonly shown by a glass gauge-tube, and by three gauge-cocks at the side, which should be opened from time to time, (especially when stopping,) as they afford a
more correct indication of the quantity of water and steam than the gauge-tube.
One pump, if constantly at work, would, in most Engines, supply as much, or rather more water than is required by the Engine as equivalent to the steam consumed; so that by turning on or off either or both pumps, the Engine-man has the power of regulating the height of the water in the boiler at discretion.
It may be laid down as an invariable rule, that water alone should always blow off from the bottom cock (which is from 1 inch to 1½ inch above the top of the fire-box), in order that there may be enough water over the fire-box and tubes to prevent their burning; and few Engines will carry their water much above the top cock without priming, so that the height of the water may be made to range between these two
points, according as more or less steam is required.
The water is higher when the Engine is running than when stopping: a good working height for it in most Engines is when water blows off from the middle cock while running, and water and steam when stopping: an Engine-man is sometimes obliged to run the water rather lower, if he has heavy work; but it is always better to keep the level of the water as high as possible.
It is observed that when any variation takes place in the pressure of the steam, a corresponding change occurs in the level of the water,—that when the pressure of the steam rises or falls, the height of the water rises or falls simultaneously. Partly for this reason, and partly to allow the more rapid generation of steam, the feed-pumps are not generally allowed to act when
the Engine starts: a knowledge of this fact also shows the necessity of the water being above the ordinary level, before a decrease is allowed in the pressure of the steam.