84 BOILER TESTS. 



pound of combustible, there is an exact agreement between the 

 two. 



The results of this comparison show that the manner in 

 which the gaseous products of the furnace appear to be con- 

 sumed, as viewed by the eye of an observer, does not necessa- 

 rily indicate much as to the true economy with which the 

 combustion takes place. As thus viewed there was a marked 

 improvement in the character of the combustion when the air 

 passages were open, over the appearance when they were 

 closed. 



The boilers developed less than their rated capacity, even 

 with a constant draught of 3-8 of an inch water pressure, 

 which is the full draught of a 100 ft. chimney. The evapora- 

 tion per pound of coal in both tests was much below that 

 obtained with the best grades of coal. This is not surprising 

 in view of the nature of the fuel, which is liable to be of 

 inferior quality. 



Boiler No. 7. 



Kind of boiler, Horizontal return tubular. 



Numb?r used, . . . . . . Six. 



Horse-power ( collective, basis 12 sq. ft. ) Four hundred and seventy. 



f Anthracite Screenings 3 parts, 

 Kind of coal, . . . . . . < _, 



I Cumberland bituminous 1 part. 



Age, Five months. 



Boiler No. 7 embraces a plant of six horizontal return 

 tubular boilers, set in one battery of brick work. The style 

 of setting is that shown in the cut of Boiler No. 6. Air is 

 supplied above the fuel through perforations in the side walls 

 and bridge wall, in the same manner as in that boiler. The 

 air ducts in this case are supplied through sheet iron pipes, 

 which are placed in the flue. These present about 3 per cent, 

 as much surface to the heat of the gases as the area of the 

 heating surface in the boilers. The air supplied above the 

 fuel is thus made to utilize some of the heat which would 

 otherwise be wasted. 



