3G4 
Utilisation of Waste Substances and 
pretty well up to the front, sometimes even well on to the 
" dead " or " dumb " plate, near the furnace-door ; and they 
are allowed to lie there to burn as best they can, throwing 
out the while huge volumes of dense black smoke at the 
chimney-head. After an interval, longer or shorter, as it may 
happen to be, for everything in this system is done by " fits 
and starts," the fire-iron is snatched up, the furnace-doors 
thrown open, and the heap of coals, half-consumed, as the 
case may be, stirred violently up, one part shoved forward 
farther on to the furnace-bars, smoke being more or less 
abundantly thrown off as the amount of unconsumed coal is 
greater or less. With this irregularity in the time of firing, 
want of uniformity in the firing is almost certain to be the 
result. It is, indeed, almost in vain to expect that the coals 
will be uniformly distributed over the surface of the fire- 
grate with such a system as that just described ; nor is it 
possible under it to prevent a very large proportion of the 
heating or available working constituents of the coal passing off 
by the chimney as unconsumed gas or fuel. This condition of 
the furnace may be likened to a gas retort, which is only heated 
in order to pass off the gaseous vapours uselessly into the 
flues, in place of conveying it to the regular apparatus, by 
xvhich the crude gases or smoke, as they are popularly called, are 
converted into a transparent or colourless gas. Now, although 
a steam-engine boiler-furnace is not practically, in the ordinary 
sense of the term, a gas-making apparatus, still in one sense it 
may really be so called, inasmuch as it is possible to be and is 
often actually such. 
To fire or stoke the Furnace, so as to prevent the formation of 
volumes of black smoke, and thus to secure the economical combus- 
tion of the Fuel and its Gases. — There is perhaps no more crucial 
ov trying test by which to judge of the efficiency or otherwise 
of the stoking of a boiler-furnace than to watch the " beha- 
viour," as engineers would say, of the chimney-flue. If this 
sends forth occasional volumes of densely black smoke, which 
continue for some time and then die away, to be succeeded alter 
a " clear interval " by fresh volumes, then it may be safely 
predicted that the stoking is bad, fitful, or irregular, anything 
but uniform, and therefore wasteful. And without going close 
to the boiler lor actual inspection, an expert can tell by simply 
watching the chimney for a time, the exact times of the firing- 
up, stoking, (Sec, gone through by the stoker. Now all this, and 
the consequent great waste, can be prevented by good stoking ; 
and this is within reach of any man of average intelligence. 
Every shovelful of coal thrown into the furnace contains so 
much carbonaceous matter within such a volume of combus- 
