120 



BOILEE TESTS. 



from either furnace are made to pass over the burning coal in 

 the other furnace, whenever either one is supplied with fresh 

 coal. Just previous to each firing the dampers are changed so 

 that the desired result may be secured. The fire in the 

 secondary furnace serves to heat and ignite the unburned gases 

 formed in the first. 



BOILER No. 18, LONGITUDINAL SECTION. 



Dimensions of Boiler No. 18. 



Diameter of shell, 



Length between heads and length of tubes, 

 Number of tubes 3 inches outside diameter, 



Area of heating surface, 



Area of grate surface ( total of two furnaces ) , 

 Area through tubes, ....... 



Height of chimney, . . . . . . 



Width of air spaces and metal bars in grates, . 

 Distance of grate to shell, . . 



Distance of bridges to shell, 



Ratio of heating surface to grate surface, 

 Ratio of grate surface to tube area, . 



48 in. 



15 ft. 

 49 



640 sq. ft. 



11.7 sq. ft. 



2 sq. ft. 



50 ft. 

 5-8 - in. 



18 in. 



7 in. 



54.4 to 1 



5.9 to 1 



