22 BULLETIN 147, I". S. BEPAETAIEXT OE AGRICULTURE. 
shoveled directly from the ear into the furnace. By using a ear the 
dust and dirt from the coal are kept down to a minimum and the 
inconvenience and unsightly appearance of coal scattered over the 
floor is prevented to a great extent. 
Ample room for working should be allowed the fireman. In many 
small plants- the space for firing Is often so limited that it is difficult 
to fire effectively. The fireman is forced to stand so close to the 
firing door and the heat from the furnace is so great that to avoid 
the heat as much as possible he stands to one side so far that he can 
not see where coal is needed, thus making it necessary to level the 
fuel bed frequently by the use of the rake. 
In firing bituminous coal the large lumps should be broken up into 
pieces about the size of a man's fist or smaller. Adding large lumps 
of coal makes it impracticable to regulate the draft so as to get an 
even flow of air through the fuel bed : especially is this true in small 
boiler plants which are fired at a slow rate and in which a compara- 
tively thin fuel bed is maintained. 
METHODS OF FIRING. 
There are three methods of hand-firing boiler furnaces, known as 
the spreading, alternate, and coking methods. 
The spreading system, which is the simplest and perhaps the one 
most commonly used, consists in spreading the coal in a thin and 
even layer over the entire fuel bed. With this system it is harder 
to prevent smoking than with the other sy-tem-. especially if too 
much coal is added at a time. Consequently, the firing should be 
done often and only a small quantity of coal fired at a time, thus 
providing for better combustion. TThen the coal is spread in a thin 
layer over the entire fuel bed the volatile gases are quickly driven off 
and burned. This system of firing is particularly applicable to small 
boilers that have only one firing door, since the entire surface of the 
fuel bed can be easily seen. A difficulty experienced with the spread- 
ing system is that, unless specially guarded against, holes are liable 
to be formed in the fuel bed near the bridge wall. A modification 
of the spreading system is sometimes used which consists in keeping 
the fuel bed much thicker at the bridge wall than at the front, thus 
preventing it from burning out so quickly. Except for the fact that 
the fuel bed is kept wedge-shaped, the firing is the same as previously 
described. In firing hard coal the spreading system is used almost 
entirely, as coal of that kind contains very little volatile matter. 
In order to prevent smoke a system of firing has been devised 
known as the alternating method. It consists in alternately adding 
coal to the front and back of the furnace or to the right and left 
sides. The object is to burn the volatile gases which are driven off 
in large volumes when soft coal is heated. By placing fresh coal on 
