l6 SCIENCE OF SUCCESSFUL THRESHING. 



is leaking because a bit of scale is preventing the valve from 

 "seating." The forcing simply presses this bit of scale or 

 other foreign matter into the seat and spoils the contact 

 surfaces so the valve will continue to leak until reground. 

 Gage-cocks and other valves on the engine should not be 

 closed very tightly when cold, for when heated, the expan- 

 sion of the metal will press the valve so tightly against its 

 seat as to injure it. 



The Water-Gage. The water-gage should be blown out 

 once each day, to clean the glass and prevent the upper and 

 lower connections from getting filled with lime or sediment. 

 To blow out the lower connection, which is the more liable 

 to become clogged, open pet cock and close upper valve. 

 Then close lower valve and open upper one, which will 

 blow steam through the upper connection and also the 

 glass, thereby cleaning it. On returning to the engine 

 in the morning, or after dinner, be sure that no one has 

 closed the valves of the water-gage during your absence. 

 If this has been done, the glass might show plenty of 

 water, while in reality, the water in the boiler has been 

 reduced to a low level by blowing off or by some other 

 cause. A stoppage in the valves, when the engine is running, 

 can be detected by the water, which will appear quite still 

 instead of moving a little, in consequence of the motion 

 of the engine. The water glass should be kept clean, even if 

 the other parts of the engine be neglected in this respect. A 

 dirty glass indicates that the engineer is careless about one 



