BOILEE No. 9. 



89 



temperature of the escaping gases was 35 6 degrees (39 degrees 

 lower than that of test No. 14 ). The evaporation from and at 

 212 degrees was 8.17 pounds per pound of coal and 9.63 

 pounds per pound of combustible. It is not certain that the 

 screenings here used was of the same quality ( though of the 

 same name) as those used in the mixture tests ; nevertheless, 

 a large gain appears to have been produced by the introduction 

 of 25 per cent, of Cumberland coal. The increase, figured 

 upon combustible, is about 11 per cent. 



Boiler No. 9. 



Kind of boiler, 



Number used, 



Horse-power (basis 12 square feet ), 



Age, 



Horizontal return tubular. 



One. 



Seventy-four. 



Two months. 



Boiler No. 9 is of the horizontal tubular type, though unlike 

 the ordinary form in being provided with a Avater leg, which 

 forms the front wall of the furnace. The arrangement of the 

 water leg, and the general features of the boiler, together with 

 the manner in which it is set, are shown in the following cuts. 

 The water leg extends a short distance below the level of the 

 grates, and at the proper point it is provided with an opening 

 through which the coal is fired. The setting is so arranged, as 

 shown, that air is supplied to the products of combustion as 

 they pass the bridge wall. The air is introduced through a 

 pipe laid inside the brick Avork, and distributed to cast iron 

 globes, Avhich rest upon the 

 top of the bridge AA^all. 

 The surfaces of these globes 

 are perforated. A jet of 

 steam is introduced into the 

 end of the supply pipe, and 

 a mixed current of air and 

 steam is thereby distributed 

 through the burning gases. 

 The size of the steam pipe 

 is 3-8 of an inch, and its 



outlet is draAvn down to a 



BOILER No. 9, CROSS SECTION THROUGH 

 FURNACE. 



