190 BOILER TESTS. 



and 9.94 pounds, allowance here being made for the superheat. 

 Notwithstanding the small size of the fire-box boiler, and the 

 foul condition of the tubes, it secured much the better result. 

 A comparison of the two tests on this boiler shows unmis- 

 takably that under equally favorable conditions, a rapid com- 

 bustion is more economical than a slow combustion. The 

 evaporation on test No. 104 with rapid combustion is less 

 than 3 per cent, below that on the other test, while the temper- 

 ature of the gases is 150 degrees higher. If the waste heat of 

 the gases had been utilized by the employment of a heater, or 

 by otherwise increasing the heating surface, the performance 

 would have been improved ( judging from the results of 

 heater tests elsewhere given ) at least 10 per cent. , thus 

 leaving 7 per cent, or more net improvement due to more 

 rapid combustion. 



Boiler No. 53. 



Kind of boiler, Vertical tubular. 



Number used, ........ One. 



Horse-power (basis 10 sq. ft. ), Seventy-five. 



Age, New. 



Boiler No. 53 is a vertical tubular boiler of the same general 

 form as that shown in the cut of Boiler No. 52. Instead of 

 being provided, however, with a fire box, as in the one 

 referred to, it has a brick furnace, and furthermore the steam 

 is discharged from the boiler immediately after its generation, 

 without passing through the interior chamber. The exterior 

 surface of the shell is protected with a somewhat inefficient 

 covering of cement. The boiler is provided with a forced 

 draught, which is produced by a blower discharging under the 

 ash pit. For the purpose of burning screenings on test No. 

 108 a plate was employed in place of the ordinary grate, and 

 this was perforated with one half inch holes, located 1 inches 

 from center to center. The tubes of the boiler were not 

 cleaned during the test, and had not been cleaned since the 

 boiler was started two weeks before. 



