4O SCIENCE OF SUCCESSFUL THRESHING 



ton of coal. A cord of soft wood, such as dry poplar or 

 pine, is equivalent to 800 or 900 pounds of coal. 



The heating value of the different kinds of wood fol- 

 lows quite closely the differences in weight and a certain 

 quantity of any kind of dry wood is about equal to 40 per 

 cent, of its weight in coal, that is, 5000 pounds of dry wood 

 is equal to a ton of coal. 



The above figures are for well seasoned sound wood. 

 If green, a considerable part of the heat is lost in evaporat- 

 ing the moisture in it; or if rotten, the fuel value is but a 

 small part of that of sound wood. 



Fuel Value of Straw. It takes from two and one-half 

 to three tons of good dry straw, such as wheat, rye, oat or 

 barley, to equal in heating value a ton of soft coal. Flax 

 straw is rich in oil and therefore has the highest heating 

 value of the various straws, but it takes more than two tons 

 even of flax straw to equal a ton of coal. 



Fuel Value of Oil. As there is considerable variation 

 in the quality of fuel oil as well as there is of coal, an exact 

 relation cannot be established. However, for ordinary 

 calculations, it is accurate enough to consider that 200 U. 

 S. gallons of oil is equivalent to a ton of soft coal. This 

 means that if oil can be purchased for 2 l / 2 cents per U. S. 

 gallon it is as cheap as coal at five dollars per ton. 



Corn Cobs. Corn Cobs make a convenient fuel as they 

 are easily handled. They make a hot fire and it is very 

 easy to keep up steam with them. Their heating value is 



