THE STEAM TRACTOR 



45 



to carbon dioxide (CO 2 ), and produces only 4480 B.t.u. instead 

 of the 14,647 which should be secured. The hydrogen burns 

 to form water (ITO), giving off 62,100 B.t.u. per pound. The 

 sulphur forms sulphur dioxide (SO 2 ), which in the presence of 

 water, finally becomes sulphuric acid and accounts for the 

 corroding effect of coal smoke on steel, for example,- on wire 

 fences along railways. 



THE TRACTION ENGINE BOILER 



Types of Boiler 



Three classes of boiler are used on steam tractors namely, 

 the locomotive or direct flue, the return flue, and the vertical. 

 In the first, which is practically universal on plowing engines, 

 the gases pass from a fire box at the rear to the smoke box in 

 front through tubes, or flues, two or three inches in diameter, 



Return flue boiler 



and thence to the stack. The boiler proper is separated from 

 the fire box and smoke box by a boiler head or tube sheet, which 

 is perforated to support the tubes. The fire box is practically 

 a part of the boiler itself, being built into the boiler shell and 



