FIRING WITH VARIOUS FUELS 39 



are similar to the "straw-burners" except that only three 

 of the arch bricks are used. The regular coal-burning 

 grates are used, but in place of dead-plates, the forward 

 two-thirds of the grate surface is covered with ordinary 

 fire bricks. These are held in place by an angle-iron bolted 

 to the grates. The fuel tank is mounted above the right- 

 hand side of the barrel of the boiler directly in front of the 

 fire-box. Its position above the boiler keeps the oil warm 

 and insures a good flow to the nozzle when the heavier 

 grades of oils are used. In firing with oil, the regular 

 fire-door is left open or removed and a sheet-steel door sub- 

 stituted, through which the burner slightly projects. When 

 oil is used as fuel, the fire must be started in the same man- 

 ner as for coal or straw, and it is necessary to have a pres- 

 sure of about ten pounds to make the burner work properly. 

 Unions are provided in order that the burner may be read- 

 ily removed for starting the fire. Fig. 10 shows how the 

 burner or nozzle is piped and also the manner in which the 

 bricks are placed in the fire-box so that no part of the boiler 

 is exposed to the direct flame. 



Fuel Value of Wood. Ordinarily a cord of the best 

 hard wood (as for example white oak) is equivalent to 

 1500 pounds of bituminous or soft coal. However, there 

 is considerable variation in even the hard woods, a cord of 

 good red or black oak being equal to about 1350 pounds of 

 coal, while on the other hand a cord of good hickory or 

 hard maple, if used for fuel, would be nearly equal to a 



