196 BOILEE TESTS. 



anthracite coal, and the mixed fuel required six times as much. 



The relative labor of firing the various coals is seen in the 

 number of times of firing and using the slicing bar. The 

 mixed fuel is at the greatest disadvantage in this respect. 



The economical results, as a whole, must take into account 

 the character of the steam, which in the various cases was 

 superheated from 73 degrees to 93 degrees. Making the 

 most favorable allowance for the increased value of the steam 

 in this condition, the results are much below that obtained 

 from the best types of boilers. The small proportion of water 

 heating surface, the consequent rapid evaporation per square 

 foot of that surface, and the resulting high temperature of the 

 escaping gases, are characteristic of this type of boiler, and 

 account for the unfavorable character of the results. 



Boiler No. 55. 

 Kind of boiler, ...... Vertical tubular. 



Number used, ...... Five. 



Horse-power (collective, basis 10 sq. ft. ), Four hundred and seventy-five. 

 Age, ........ One year. 



Dimensions of Boiler No. 55. 



Diameter of shell, 04 in. 



Length between heads and length of tubes, . . . . 14 ft. 

 Number of tubes ( collective ), 3 inches outside diameter, . 420 



Area of water-heating surface, 3,300 sq. ft. 



Area of steam-heating surface, ...... 1,455 sq. ft. 



Area of total heating surface, 4,755 sq. ft. 



Area of grate surface, 157.5 sq. ft. 



Area through tubes, ......... 17.2 sq. ft. 



Area through flue, . . . . . . . . . 27.1 sq. ft. 



Distance of grate to tube sheet, 3 ft. 7 in. 



Ratio of water-heating surface to grate surface, . . . 29.0 to 1 

 Ratio of steam-heating surface to grate surface, . . . 9.2 to 1 

 Ratio of grate to tube area, . . . . . 9.1 to 1 



