H. Sxey.—Smokeless and Self-feeding Furnace. 31 
imparted to a substance at a lower heat requiring it and we utilize the obscure 
heat, whether it be 1? or 500?, while, at the same time, the luminous heat 
in the furnace is vastly augmented, and can act quicker by conduction and 
radiation upon the contents of the boiler. 
The bottom of the furnace is made concave upwards, and is formed by the 
boiler-plate itself, so that the water is brought close to that part where ignition 
is the strongest, which could not be effected in a furnace with fire-bars. 
Steam will be generated at this part of the furnace with immense rapidity, 
for not only have we radiation of the heat, but conduction too. A number 
of tubes convey the hot blast upwards, in a convergent direction, through this 
part of the boiler into the furnace, and these tubes or tuyéres, together with 
the bottom of the furnace, are kept from overheating by the water in the 
boiler. To prevent the possibility of the spheroidal condition being imparted 
to the water from the intense heat, this part of the boiler is roughened 
internally to facilitate the vaporization and agitation of the water; and, still 
further to insure safety against explosions and to prevent priming, a certain 
amount of the evolved gases from B, above the ash-pit, are conveyed into the 
boiler near this part of the furnace, either directly by а pump, or into the 
feed water, or else into the distilled water of the surface condenser, if 
one be used. From the repeated vaporizations and condensations of the water 
in the surface condenser it is deprived of its air, and its boiling point is thus 
raised from its increased cohesion ; but when it is charged with these gases, 
which it quickly absorbs, then ebullition takes place from the bottom and 
from all parts of the boiler, and this at a less temperature and with more 
regularity. 
Fresh fuel is added by placing it between doors in front of the furnace, 
one of which is shut when the other is opened, which serves to keep it 
sufficiently air tight when fed, at the same time preventing loss of heat by 
radiation, and rendering it cooler for the fireman ; and sufficient fuel is added 
so that it falls in the proper form of heap of itself, and covers all the tuyéres 
but one to a proper depth. The tuyere which is not covered delivers hot air 
among the evolved gases, and, therefore, instead of cooling them and thus 
forming smoke, as cold air would, it heats them and ensures their combustion ; 
and this is effected without cooling the sides of the furnace and boiler. If the 
fuel be lignite, it will not need stirring, neither will there be any clinkers 
formed to need removing. 
The use of the blast allows the furnace to be made smaller, and because 
heat varies inversely as the square of the distance, it is obvious that intensity 
of evaporation of the water is increased by being brought nearer to the centre 
of heat ; and because the density or elasticity of the air is diminished one-half 
for an increase in temperature of 491° F., therefore it will require discharging 
