BOILER No. 15. HI 



Chestnut, $8 00 



Pea, 7 32 



Broken, 8 15 



Cumberland, 791 



Mixed fuel, 5 48 



According to this basis of comparison, which may be called 

 the commercial basis, the cost with pea coal is reduced $0.32 

 or 8.5 per cent. ; that with broken coal is increased $0.15, or 

 1.9 per cent. ; that with Cumberland is reduced $0.09, or 1.1 

 per cent. ; and that with the mixture is reduced $2.52, or 31.5 

 per cent., these being all compared with the cost when using 

 chestnut coal. Although this comparison does not apply to 

 the present time, when prices of coal are altogether different, 

 the figures are suggestive as to the influence which cost has 

 upon the actual value of a given kind of coal. 



The varying amounts of ash which different sizes of anthra- 

 cite coal, and the different classes of other coals contain, is 

 exhibited by these tests. The pea coal contained the largest 

 quantity, viz : 15.8 per cent. ; and the broken coal the smallest 

 for the anthracite class, viz : 10.5 per cent ; while the bitumi- 

 nous George's Creek Cumberland gave 6.6 per cent; and the 

 mixed fuel 11.4 per cent. The last is low for this class of 

 fuel and an indication of good quality. There is a noticeable 

 difference in the effect of the various fuels on the temperature 

 of the escaping gases. The Cumberland and mixed fuels gave 

 a higher temperature than that produced by the anthracite 

 coals. This condition is almost always observed in fuels made 

 up in whole or in part of bituminous coal. 



Another series of tests was made on Boiler No. 15, the 

 object of which was to determine the effect upon the economy 

 of different fuels produced by admitting air at the bridge wall. 

 These are numbered from 40 to 45 inclusive, and the data and 

 results are given in the appended table. The method employed 

 in supplying air, consisted in introducing it through a pipe 7 

 inches in diameter running through the side wall, at a distance 

 of 26 inches below the top of the bridge wall. The pipe 

 entered a chamber formed by building a new wall a few inches 

 behind the bridge and covering the top of the intervening 



