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The smoke ami sparks that are discharged from the locomotive are so annoying to 
passengers that on some of our lines a trip hy rail on a hot day is something to he 
dreaded, and the danger to forests and other property from fires set hy these sparks 
is, in the aggregate, enormous. 
To the novice the remedy for all this would seem to ho to so arrange the furnace 
that perfect combustion would take place. This may he done on stationary or marine 
engines, where healing surface enough can he provided to allow of slow and perfect 
combustion, hut in the locomotive the weight and size of hoiler is limited and artiti- 
cial means must he used to provide for such rapid comhustiou as is required when the 
engine is developing its full power. 
The attention of locomotive mechanics has heen drawn to this question of fuel- 
combustion ever since the hirth of the locomotive, hut their efforts to make it perfect 
have heen only partially successful, and while the heating surface of our hoilers is so 
small in comparison with the requirements of the engines a forced draft will have to 
he resorted to. This fact heing recognized, it necessarily follows that when the en- 
gine is developing its full power the artificial draft is so strong that small particles of 
coal will he lifted from the fire and drawn through the flues unconsumed and dis- 
charged out of the chimney in the form of what is called sparks. The fact that some 
solid matter will he dra wn through the flues from the fire heing established, I will 
now briefly consider the various mechanical contrivances that have from time to time 
been brought forward to arrest and dispose of these solids. 
Among the earliest contrivances (when wood was the universal fuel used in this 
country) was a chimney shaped like a funnel placed with the broad mouth upward. 
This broad end was covered with a wire screen, and inside of this chimney was placed 
a straight pipe somewhat smaller than the smallest diameter of the eh imney, its height 
being about two-thirds that of the chimney. Over this, and near the wire screen, 
was mounted a deflecting plate with edge3 curving downward. A spark-reservoir 
was placed in some suitable position near the smoke-box, and pipes were made to lead 
from the annular space between the chimney and the inside pipe to this reservoir. 
The operation of this arrangement was as follows: 
The unconsumed products of combustion that were drawn through the flues were 
driven by the exhaust steam upwards against the curved deflector at the top of the 
chimney, and the larger and heavier particles were forced down and into the spark- 
reservoir. The lighter particles would pass to the atmosphere through the wire screen, 
hut would ra'rely have life enough to set anything on fire. The reservoir, however, 
was soon abandoned, as it was found in practice that with wood for fuel the sparks 
were so reduced in size by friction in their passage through the flues and chimney 
that. they could all pass through the screen to the atmosphere with little danger of 
setting fires. 
When coal came to be used as fuel the old arrangement of chimney was found to 
be unsuitable, and new appliances had to be devised. A hew and annoying element 
had to be met— that of gas and smoke, caused by imperfect combustion in the furnace. 
When fresh coal is added to the fire a vast quantity of gas is evolved and unless a 
sufficient quantity of atmospheric air is brought into immediate contact with it, it 
will pass off in the form of smoke. 
Various plans to furnish the requisite amount of air, and at the proper time, have 
been tried, but the varying conditions under which the engine is working have so far 
made it practically a failure. 
Letting air into the furnace over the fire, while it will prevent the formation of smoke 
if let in in sufficient quantity, will also lower the steam-producing qualities of the 
boiler. Air mixed with a jet of steam driven into the furnace over the fire has been 
tried at various times and in various ways, but it has always ended in failure. D. 
K. Clark, the eminent English engineer and author, in his work on the locomotive, 
describes a method of injecting air and steam mixed into the furnace of a locomotive 
boiler to promote the combustion of the gases. 
