H. 8key.— Smokeless and Self-feedincj Furnace. 31 



impai'ted to a substance at a lower heat requiring it and we utilize tlie 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 tuyhres, 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 watei- ; 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 a pump, or into the 

 feed water, or else into the distilled, water of the surface condense!', 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. 



Eresh 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 

 safl&ciently 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 tuyeres 

 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 I'emoving. 



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 l»rought 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 



