BOILER No. 17. 



119 



the evaporation per pound of coal. Basing the results on the 

 cost of fuel required to produce 30,000 pounds of steam from 

 and at 212 degrees, according to the prices which ruled at the 

 time of the tests, the figures are as follows : 



Broken. 



Pea. 



Mixture. 



In this comparison the economy of pea coal is 18 per cent, 

 over broken coal, and that of the mixture 26.9 per cent, over 

 the same fuel. 



It is to be noted that the amount of draught required on the 

 test with mixed fuel was 0.28 inches measured in water pres- 

 sure, while that required on the other tests was 0.11 and 0.12 

 inches respectively. The labor of firing with mixed fuel was 

 much greater than in the case of the others, both the number 

 of firings and the number of times that the slice bar was used 

 being relatively large. 



Boiler No. 18. 



Kind of boiler. . 

 Number used, . 

 Horse-power ( basis 12 sq. ft. ) . 

 Age, ...... 



Horizontal return tubular. 



One. 



Fifty-three. 



Six months. 



Boiler Xo. 18 is a horizontal tubular boiler with a special 

 arrangement of setting, the general features of which are 

 shown in longitudinal section in the following cut. A furnace 

 is placed under each end of the boiler, located in the same 

 manner with reference to the boiler as the furnace in the 

 common horizontal boiler. A damper is provided in each 

 front connection for the control of the flue gases, and another 

 above each furnace at the entrance to the chamber in front of 

 the tubes, to control the passage of the products of combus- 

 tion into the boiler. The method of operation consists in 

 firing the furnaces alternately. The products of combustion 



