THE SMOKE NUISANCE. 481 
The size or dimensions of flues, breeching, and chimneys, must coincide 
with the conditions and regulations of the furnace. 
In firing, my preference is toward that method known as the coking process, 
/. (?., pushing toward the rear of the firebars the already " live" coals, and plac- 
ing the green coals in front, so that the gases arising from them in coking may 
be consumed in passing over the incandescent fuel. In this opinion I am upheld 
by many authorities. 
' When fresh coal is placed in a bright boiler furnace various hydrocarbons 
are given off. In coming in contact with the oxygen of the atmosphere, at the 
proper temperature, they are converted into water and free carbon — the hydro- 
gen uniting with the oxygen at a lower temperature than does the carbon. This 
latter becoming united with a further quantity of oxygen is then converted into 
carbon dioxide. The carbon dioxide, passing on toward the rear of the furnace, 
meets with red hot carbon and becomes carbon monoxide. Some of it, however, 
passes on to the chimney without alteration. The carbon monoxide, if supplied 
with still more oxygen, will be reconverted into carbon dioxide, though this, as 
before stated, is never completely accomplished. The difference, then, between 
complete and incomplete combustion is, that in the former, no carbon (soot) and 
very Uttle carbon monoxide are produced \ whilst in the latter case carbon (soot) 
and much carbon monoxide are given off. 
Devices for Abating the Nuisance. — Their name is legion. Permit me, 
however, to enumerate some of the principles on which they are founded : 
ist. Automatic firing. This is an excellent principle. 
2d. Alternate firing; also considered very suitable. It consists in having 
two separate furnaces and sets of firebars, etc. A is fired and the gases compelled 
to pass over or through the incandescent fuel in B, and vice versa. 
3d. Sloping bars, either toward the front or rear, or laterally upward or 
downward, considered favorably by those who prefer the coking method of 
firing. 
4th. Movable firebars. These may be either on the principle of an endless 
chain or of a rotary fire-grate. Liability to get out of repair and expense in the 
matter cf fuel militate against them. 
5th. The coking principle, already spoken of. 
6th. Washing the products. This gets rid of the nuisance so far as the 
mechanical objections are concerned, and some, though not all, of the chemical. 
It has, however, been entirely discarded in Europe. 
7th. High chimneys have been recommended by some, but in my opinion 
have not fulfilled what was promised for them. 
8th. Air currents. There is a great variety of these, both hot and cold, 
from front impinging on the flame, laterally also on the flame, laterally through 
the bridge-wall, and from the rear through the bridge-wall. Some are introduced 
by means of steam-jets, whilst some are passed in dry by means of the natural 
draughts. 
9th. Deflectors. These are brick or metal projections from beneath the 
