Dr Fyfe on the Evaporative Power of Coal. 269 



choke up. the spaces between the fire bars, and also the flues, 

 and in a great measure prevent the combustion from going on. 

 Though it can be burned in common grates, yet, unless con- 

 sumed in some particular way, it does not answer well for 

 raising steam, owing to the slowness of the combustion. A 

 patent was lately taken out by Mr Player for effecting the con- 

 sumption of anthracite, by previously heating the coal, by 

 making the part of the apparatus containing the fuel to be 

 supplied to the furnace, pass through the boiler, by which 

 means it derives heat from the water. The method I adopted 

 was to supply the coal with air previously warmed, which was 

 done by making it traverse the apparatus already described, 

 and by which the temperature was on an average about 350°. 

 By this contrivance, the decrepitation was almost entirely pre- 

 vented, the combustion was rapid, and the steam was easily 

 kept up. I have already mentioned that [the anthracite I em- 

 ployed was of inferior quality ; it contained not only a large 

 quantity of ash, but also of volatile matter, the latter of which 

 made it burn with flame, while the former, owing to the in- 

 tense heat generated, formed a tough slag, which adhered 

 firmly to the bars, and in a great measure retarded the com- 

 bustion. 



The trials were conducted with the coal without being picked. 

 Numerous experiments were made with the furnace when fit- 

 ted up with the flash-flues, but with this the draft was evi- 

 dently deficient, and the furnace was therefore taken down 

 and rebuilt with the returning flue, and an addition made to 

 the chimney to bring it to the height formerly mentioned, by 

 which I found that the evaporation was considerably increased. 

 Being totally unacquainted with the burning of anthracite, itwas 

 necessary, before beginning to record the results of any trials 

 with accuracy, to find out the best means of accomplishing the 

 combustion. As go od anthracite burns with little or no flame, 

 and as, of course, there is no bituminous matter, which causes the 

 swelling of other kinds of coal, I found that the furnace bars 

 must be brought noarer to the bottom of the boiler, than when 

 Scotch or English caking-coal is employed. In my experi- 



vol. xxx. no. lj:. — ArniL 1841. , s 



