BOILER No. Id. 109 



13 and No. 14 already noted, there is an appreciable difference 

 of economy in favor of the medium capacity. Here it is about 

 three per cent. There is a notably low temperature of the 

 escaping gases compared with that found in the other two 

 boilers worked at maximum capacity, due, no doubt, in part, 

 to the relatively large extent of heating surface, and in part to 

 the cleanliness of the surfaces which presumably existed in the 

 new boiler. Still, this favorable indication is accompanied by 

 a comparatively low evaporative result. The large space 

 behind the bridge and the greater radiating surfaces thus 

 exposed does not appear to be adequate to produce an unfav- 

 orable effect of much consequence , but there appears no other 

 cause. It is noted that a higher rate of combustion is secured 

 in Boiler No. 15 than in the others. This may be attributed 

 to the newer and tighter condition of the flues leading to the 

 chimney. One chimney of ample area served for all three 

 boilers. 



A series of tests was made on Boiler No. 15 to compare the 

 economy of different fuels. These are numbered from 35 to 

 39 inclusive. With the exception of Test No. 39 made with 

 mixed fuel, none of these are capacity tests. On all the tests 

 except this one, the damper was partially closed. The results 

 are given in the appended table. 



Taking the results with chestnut coal as a basis of compari- 

 son, and figuring on the evaporation per pound of coal, the 

 pea coal lost 9 per cent. ; the broken coal gained 4.2 per cent. ; 

 the Cumberland coal gained 19.3 per cent., and the mixed fuel 

 gained 6.2 per cent. 



Considering the cost of these fuels given below, as quoted 

 at the time of the tests ( per ton of 2,240 pounds ), 



Chestnut, $5 50 



Pea, 4 00 



Broken, 5 85 



Pea and Dust, 2 75 



Cumberland, G 50 



the total value of the fuel used in evaporating a given quantity 

 of water, say 30,000 pounds from and at 212 degrees, accord- 

 ing to the results here obtained, is as follows : 



