38 SCIENCE OF SUCCESSFUL, THRESHING 



Peep Hole. All "Case" boilers except the eighteen 

 and thirty H. P. have an opening on the left side near the 

 front of the fire-box known as the "peep hole." This is 

 used on straw-burning boilers to allow the operator to 



USIBLE PLUG 

 O O O O 



TUBE HEAD 



FIG. IO. SECTIONAL VIEW OF FIRE-BOX FOR BURNING OIL. 



observe the flame passing over the brick arch and to re- 

 move straw from the tube-ends in case it is drawn over the 

 brick arch. As with the fire-door, the peep-hole should 

 not be kept open longer than necessary. 



How to Fire with Oil. The "Case" oil-burning engines 



