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Recent so-called inventions brought out in this country are almost exact duplicates 
of appliances described by Clark long ago. 
Rotary blowers have been used to drive the products of combustion from the smoke- 
box back to and into the furnace to be subjected to a reburning process, but such 
methods never got beyond the experimental stage. Double or twin furnaces have 
been tried, but while producing good combustion the mechanical difficulties to be 
overcome have thus far interfered with their success. Several years ago mechanical 
devices of various forms were quite largely used for driving the solid, unconsumed 
products of combustion from the smoke-box back through suitable tubes to the fur- 
nace, but they have nearly all given way to more modern and better methods. 
I will now proceed to discuss the most approved methods of promoting combustion, 
and also the mechanical means employed to prevent the escape of sparks from the 
chimney. And here let me say, curious as it may seem, the wonderful discoveries 
made in the last twenty years in the production of steel have a direct bearing on the 
question under discussion. 
The substitution of steel for iron in rails and tires has made it possible to so increase 
the weight of the locomotive that larger boilers can be used, and therefore a very much 
greater heating surface in proportion to the cylinder area. This fact makes it possible 
to do what could not be done were soft-iron rails and tires still in use. 
The modern locomotive boiler has little to distinguish it from its prototype of thirty 
years ago. All combustion chambers, water tables, and complications of all kinds 
have been discarded, and we have the plain rectangular furnace, with plenty of tubes 
to freely carry off the products of combustion. Its leading feature is its size and 
large heating surface. Its enormous evaporative power will be recognized when I 
say that this boiler, when pushed to its full capacity, will convert ,3,000 gallons of 
water per hour into steam. To accomplish this amount of work on a grate surface of 
only 18 square feet, very rapid combustion must be maintained, and this can be done 
only by a forced draft. A forced draft means imperfect combustion, and imperfect 
combustion means particles of unconsumed coal drawn through the tubes. These 
unconsumed solids must be arrested in their course to the atmosphere and deposited 
in receptacles where their presence will not be harmful. This is measurably accom- 
plished by the use of the appliances shown in the drawings. The smoke-box is made 
twice the usual length ; a coarse wire-screen is drawn across high enough to be above 
all the boiler flues ; the chimney is a plain, open pipe, smooth and free from obstruc- 
tions ; the exhaust pipes are carried up through the screen, terminating in a single 
nozzle. In front of the flues a deflecting plate is placed at a suitable distance from 
the ends of the flues, and is set at an angle of about twenty degrees. The functions 
of this plate are twofold — first, it equalizes the draft through the flues ; and, second, 
it deflects the sparks downward, and instead of their being shot upward through the 
chimney they are banked up in the forward end of the smoke-box, there to remain 
until they are removed ab the end of the trip. In the furnace is placed a fire-brick 
arch, extending entirely across the furnace and from the flue-sheet under the flues 
back about two-thirds of the length of the furnace. The gases, as they arise from the 
coal, are forced to travel back and over this arch on their passage to the flues, and by 
the delay thus caused, and also by their contact with the intensely hot fire-brick com- 
posing the arch, are very thoroughly consumed. The unburned solids lifted from the 
fire are also prevented from being drawn directly into the flues, the force of the draft 
caused by the exhaust steam in the chimney causing them to impinge against the hot 
brick, where the heat is so intense that a large percentage of them are consumed that 
would otherwise be drawn through the flues in a solid state. The brick arch is sup- 
ported on four iron tubes, placed diagonally in the furnace, connecting the water- 
space under the flues with the water over the furnace crown. These tubes not only 
make a reliable support for the brick, but best promote the circulation of the water 
in the boiler. 
The arrangement of smoke-arch described is not of recent design, but was patented 
