14 
Steam Engine, 
a (Fig. 7 and 8), placed at a small distance, or from about 
three-eighths to three-fourths of an inch from the upper 
side of the hopper, betwixt which plate, and upper plate, 
or side of the hopper, a stream of air rushes downward on 
the fire, at about half a right-angle to the horizon, which 
stream of air assists in consuming the smoke, as former* 
ly mentioned, and more fully described hereafter. B, Fig, 
7, is a section of the bars, which are, in general, a little 
inclined to the horizon, as in the figure that the fuel may 
more easily fall, or be pushed backwards, in the furnace ; 
at c, is an opening above the bars, and below the lower 
end of the hopper, which is in general fitted with a grated 
door or doors, which open for the more convenient clean- 
sing of the furnace, and the grated form of the doors is 
also designed for admitting air into the fuel, as well as at 
the bars, consequently the air is more concentrated in the 
middle of the burning fuel, and produces a greater heat 
than if admitted only betwixt the bars ; this grated form 
of the doors is also convenient for the admission of a poker 
or instrument for pushing backward the kindled fuel, while 
the fresh coal, or that which is not so well kindled, falls 
down to supply its place ; in some others of these furna- 
ces, the opening below the lower end of the hopper, and 
above the fore end of the bars, is left without dpors at all; 
at this opening, it is convenient, when the fire is mended, 
to push the coal frcrm the fore side backward, as mention- 
ed above, or it may be pushed backward with a hooked 
poker, P, by applying the hooked part of it through the 
furnace bars below ; by either of which means the kindled 
coals are put backwards, while the fresh coal, or that 
which is not so well kindled, falls down to supply their 
place ; that is, the coals, in the situation c, are pushed 
towards d, while those in the situation f fall down to sup- 
ply the place of those which were driven from c towards d; 
by such means, the strength or heat of the fire is not much 
