23. Q. In what condition should the fire be in order that the best
results may be obtained from the combustion of the coal?

A. The fire should be as light as the work being done by the engine will
permit, evenly distributed over the grates and free from clinkers.

24. Q. How should the blower be used?

A. A blower should be used very lightly, being careful not to draw too
much air into the fire-box and through the flues, especially when fire
is being cleaned or thin on grates.

25. Q. What is the result of opening the fire-door when the engine is
working steam?

A. It will cause a cooling effect in the fire-box and is liable to start
the flues leaking.

26. Q. What is the effect of putting too many scoops of coal on a bright
fire? Is this a waste of fuel?

A. It has the effect of temporarily deadening and cooling the fire,
causes emission of quantities of black smoke, as only a limited amount
of gas can be burned in a fire-box at a time; all in excess of that
amount escapes from the stack and is a waste of fuel.

27. Q. What effect has the fire upon a scoopful of coal when it is
placed in the fire-box?