FARM MOTORS 



Semi-anthracite coal. This variety has properties that 

 make it to be considered a medium between anthracite 

 and soft coal. It burns very freely with a short flame. 



Bituminous or soft coals. These burn freely and with all 

 gradations of character. Their properties are so varied 

 that they will not permit of classification. Some burn 

 with very little smoke and no coking. This class is gen- 

 erally used in traction engines. Others which coke very 

 freely are good for gas making. 



Wood is used only where it is more plentiful than coal. It 

 requires a finer meshed grate than coal and more atten- 

 tion in feeding. 



Oil. In localities where oil is plentiful or where it is 

 cheaper to freight oil than coal, furnaces are fitted for it 

 as a fuel. It has been found that oil burns the best when 

 atomized and mixed with steam. For this purpose a 

 nozzle is constructed so that both steam and oil can flow 

 from it, the steam forming an oily vapor of the oil, which 

 when ignited burns with a very intense heat. 



Straw. In localities where straw is practically worthless 

 and coal and wood are scarce, straw is used as a fuel. It 

 must be handled with care, since too much in the fire box 

 at once is as harmful as not enough. 



476. Value of fuels. Anthracite and semi-anthracite 

 coals have about the same heating value. Bituminous 

 has a trifle lower value. A cord of hard wood has the 

 same amount of heat in it as a ton of anthracite coal, 

 while a cord of soft wood has only about half that value. 



COMBUSTION 



477. The term combustion as ordinarily used means the 

 combining of a substance in the shape of fuel with oxygen 

 of the air rapidly enough to generate heat. In all fuels 

 there are hydrogen and carbon, and some mineral matter. 



