BOILEE No. 56. 199 



tion from the brick furnace, and by leakage of air through the 

 brick work. The large area through the tubes doubtless con- 

 tributed in some degree to the unfavorable result. 



The low draught required for a vertical boiler is here notice- 

 able, 16 inches being sufficient to burn 14.3 pounds of anthra- 

 cite coal per square foot of grate per hour. In the case of the 

 test with the mixed fuel the draught suction was .03 inch. 



Comparing the results of test No. 116, made with mixed fuel, 

 with that of No. 115, made with anthracite coal, the evapora- 

 tion with the mixture, based on coal, is 5 per cent, less, and 

 based on combustible, 1 per cent, less, than that with the 

 standard fuel. Taking into account the cost of these fuels at 

 the time of the tests, the economy in favor of the mixed fuel 

 amounts to 33 per cent. 



Boiler No. 56. 



Kind of boiler, Vertical tubular ( nest ). 



Number used, Two. 



Horse-power ( collective, basis 10 sq. ft. ), Three hundred and eighty. 



Kind of coal, Anthracite chestnut No. 2. 



Age, Ten years. 



Dimensions of Boiler No. 56. 



Diameter of central shell, 36 in. 



Length of central shell, 21 ft. 



Diameter of outer shells ( 6 in number, each ), ... 30 in. 

 Length of outer shells and length of tubes, . . . 10 ft. 



Number of tubes ( collective), 2 inches outside diameter, . 516 

 Area of water-heating surface, . ...... . . . 2,224 sq. ft. 



Area of steam-heating surface, ...... 1,566 sq. ft. 



Area of total heating surface, 3,790 sq. ft. 



Area of grate surface, ........ 143 sq. ft. 



Area through tubes, . 8.6 sq. ft. 



Area through flue, ......... 10 sq. ft. 



Ratio of water-heating surface to grate surface, . . . 15.5 to 1 

 Ratio of steam-heating surface to grate surface, . . . 11 to 1 

 Ratio of grate surface to tube area, 16.6 to 1 



