H. Skey. — Smokeless and Self-feeding Furnace. 27 



clean and glowing fuel remains, and is by the same means supplied "with a 

 constant stream of oxygen ; heat of any I'equired intensity is thus produced, 

 which can be adjusted by regulating the blast. If we take the experimental 

 quantity of 1 "5 tons of lignite, and consume it in twenty -four hours, then the 

 furnace must be supplied with a charge of 1 4Ibs. of fuel every six minutes, 

 and as this fuel yields on analysis 5 "5 per cent, of ash, it follows that only 

 |B). of ash requires removing and carrying along with the draught in the 

 six minutes. 



We may now consider whether there is really any loss of power, and, if so, 

 how much, by the use of a blast. By its use, the tall chimney is, of course, 

 dispensed with. It may be thought that the draught caused by oi^dinaiy 

 chimneys costs nothing ; but is it not a fact that a certain amount of motive 

 force, or its equivalent of heat foi'ce, is used in the act of causing a draught in 

 common chimneys, and that if all the heat of the furnace were really utilized 

 (as by evaporating the theoi'etical amount of water, for instance), there could 

 then be no heat left to expand the column of air in the chimney to work the 

 draught, for the gases evolved would be no hotter than the ordinaiy 

 temperature of the atmosphere % The modern theory of heat shows that in 

 whatever manner work is done, if work be done at all, then its equivalent of 

 heat force is expended. Now, the column of ascending gases and air in a 

 chimney is continually pushing away the atmosphere and making room for 

 its passage through it. The furnace may be taken as so much colder by 

 that amount, that is, there will be that amount of heat less that can be used 

 for evaporating the water. 



Experiment No. 1. — In a closed furnace, specially arranged so that no air 

 could pass into it except through the burning fuel, a thermometer was attached 

 so that the bulb projected into the furnace about 3 in. above the fuel, until it 

 showed a constant temperature of 286'^, with the damper open ; then, on 

 shutting the damper in the chimney, in seven minutes it rose to 358° ; then 

 opened it a very little, the temperatiire at once fell proportionately to the 

 amount that the damper was opened ; on opening it wider, it fell to 285° ; 

 then completely closed it, when it rose in three minutes to 320°. This 

 experiment was varied with like results. Also, on another occasion, when the 

 thermometer was removed and a vessel of water placed on the top, it 

 commenced boiling when the damper was shut, and immediately ceased when 

 it was opened. This was repeated several times, which results may be 

 ascribed principally to the fact of the gases above the fire being more easily 

 heated under the extra pressure when the damper is shut ; for when it is 

 opened, then some of the heat can exert itself in expanding the gases in the 

 chimney, and thus disappears. Now let the chimney be removed and the fire 

 supplied with the same amount of air from a blast, and there can be no moi-e 



