188 



BOILER TESTS. 



being filled with water. When 

 the boiler is in operation, there is 

 a circulation of water from the 

 bottom of the boiler upward 

 through these annular spaces, to 

 the top of the boiler, and thence 

 downward through an outer row 

 of tubes, which are provided for 

 the return of the water. The 

 upper ends of the fire tubes are 

 bare, and the steam, on leaving 

 the steam space, is by this means 

 superheated. Owing to the sub- 

 sequent passage of the steam 

 through the drum, the superheat 

 is absorbed, and the steam leaves 

 the boiler in a saturated state. 

 The boiler is surmounted by a 

 smoke stack, which is so placed 

 that it interfered with the clean- 

 ing of the tubes, and these had 

 not been brushed out since the 

 boiler was started. 



BOILER No. 52, VERTICAL ELE- 

 VATION AND SECTION. 



Dimensions of Boiler JVb. 52. 



Diameter of shell, 



Diameter of fire-box and grate, .... 

 Height between heads and length of tubes, . 

 Number of tubes 2 inches outside diameter, . 



Height of fire-box, 



Area of heating surface (trtal), .... 

 Area of grate surface, ..... 



40 in. 

 33 in. 

 9 ft. in. 

 42 



24 in. 

 205 sq. ft 

 6.1 sq. ft 



