l8 SCIENCE OF SUCCESSFUL THRESHING 



with lime and should always be in working order. When- 

 ever opened, the steam should be allowed to blow through 

 a sufficient time to clean them. They should then be closed 

 moderately tight, and then, if they leak, they should be 

 opened again to allow any dirt or scale that may have 

 lodged on the seat to blow out. It is not well to force a 

 gage-cock or other valve shut to stop it from leaking, for 

 probably it 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 expansion 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 up- 

 per 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 ab- 

 sence. If this has been done, the glass might show plenty 

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



