30 SCIENCE OF SUCCESSFUL THRESHING. 



injector, but if the boiler be too full, the damper may be 

 closed. Another way is to open the fire door an inch, 

 leaving the damper open, but the door should never be held 

 open more than this amount. This will do no harm to tubes 

 or boiler, but never open the door and close the damper at 

 the same time, when the engine is running. When the 

 engine is to be shut down for any length of time the smoke- 

 box door may be opened to check the fire. 



Some grades of coal will form clinkers that cover the 

 grates and shut off the air siipply. These must be kept 

 out by removing through the fire door, but do not use the 

 poker when it can be avoided, or keep the door open longer 

 than is necessary. When troubled with clinkers, make it a 

 point to clean the fire at noon or at any time the engine may 

 be stopped. The tubes should be cleaned at least once a 

 day. 



One or two of the bricks for straw burners can be used 

 to advantage in burning coal. They make better combustion 

 with poor coal, render the fire easier to control and by main- 

 taining a more uniform heat in the fire-box, are easier on the 

 boiler. 



Firing with Wood. The manner of firing with wood 

 depends entirely upon the fuel, and must be learned by ex- 

 perience. When the wood is soft, or the sticks small or 

 crooked, it will be necessary to lay the pieces as compactly 

 as possible, and keep the fire-box full all the time. Straight, 

 heavy sticks of hardwood, on the other hand, must be placed 



