24 ANNUAL OF SCIENTIFIC DISCOVERT. 



the subject, it does seem remarkable that so little has been done 

 in this direction. Of the different lire-feeding machines, as they 

 have .been called, that have been employed at different times, I 

 think I am correct in stating that, excepting the one I wish to 

 bring under your notice, Juckes' Endless Chain Grate is the only 

 one that has received any considerable amount of approval. Of 

 the performance of this furnace very conflicting accounts are 

 given ; but I believe that under favorable conditions as to fuel, 

 management, and work to be done, when applied to externally 

 fired boilers the performance of this furnace has been found sat- 

 isfactory. Although the Juckes' grate does, under favorable cir- 

 cumstances, prove the superiority of mechanical over hand stok- 

 ing, yet it does not, I think, sufficiently meet the engineering 

 requirements of the present time ; it has one serious defect : it is 

 only applicable to externally fired boilers, and is very cumbrous. 

 Before describing particularly our furnace, I will speak of what 

 I conceive ought to be aimed at in constructing a mechanical 

 stoker. 



"The late Mr. Charles Wye Williams, who has done so much 

 to diffuse and popularize correct views on the subject of furnace 

 management, writes, in his work on the combustion of coal and 

 the prevention of smoke : ' The facility with which the stoker 

 is enabled to counteract the best arrangements naturally suggests 

 the advantage of mechanical feeders. Here is a direction in 

 which mechanical skill may be successfully emploj^ed ; the basis 

 of success, however, should be a sustaining at all times the uni- 

 form and sufficient depth of fuel on the bars.' This is correct so 

 far as it goes, but a mechanical stoker, to be successful, must do 

 more than this : it must preserve the air spaces of the fire grate 

 uniformly open, be self-cleansing by discharging the ashes, slag, 

 or clinker as formed ; and, in addition, I think it is important that 

 the fuel should be introduced at the front of the furnace, and 

 should have a progressive motion towards the bridge. The ad- 

 vantage of introducing the fuel at this part, as a means of insur- 

 ing economy and preventing smoke where bituminous fuel is 

 used, has been proved conclusively by numerous experiments. I 

 suppose the cause of this is the long run of the volatile hydro- 

 carbons over the incandescent fuel that fills the bridge part of the 

 furnace. It is also important that the machine stoker should be 

 easily regulated and controlled for the purpose of adjusting the 

 supply of fuel to the work to be done, and that it should be very 

 little liable to derangement, or wear and tear. I think our appa- 

 ratus fulfils all these conditions. Like all fire-feeding machines, 

 it is provided with a hopper or fuel receptacle ; the fuel is forced 

 into the furnace by two plungers or pushers (having an alternate 

 motion) at a level of about 6 inches above the bars. In very 

 wide furnaces we use 3 plungers, and the shaft that works the 

 plungers is moved by a ratchet. A very simple arrangement 

 enables the attendant to vary the rate of feed by causing the div- 

 ing eccentric at each stroke to take a lesser or greater number of 

 teeth. Progressive motion is given to the fire by causing the bars 

 to move forward en masse, and bringing them back in detail. The 



