164 MARKET DAIRYING 



burned in the form of gases. If, on the other hand, too 

 much air is admitted the excess simply passes through 

 the chimney, absorbing heat as it pasSes through the 

 boiler. The problem of firing becomes, therefore, a diffi- 

 cult one. 



Burning Coal and Wood. When hard coal is burned 

 the fire should be thin. A thickness of three to four 

 inches on the grates gives very satisfactory results. For 

 best results with soft coal a thickness of six to seven 

 inches is recommended. Whenever fresh coal is added it 

 should be placed near the front and the hot coals pushed 

 back. 



In case wood is burned the fire box should be kept well 

 filled, care being necessary to keep every part of the grates 

 well covered. 



gen£;rai, pointers on firing. 



1. 'Boilers newly set should not be fired within two or 

 three weeks after setting and then the firing should be 

 very gradual for several days to allow the masonry to 

 harden without cracking. 



2. Never fire a boiler before determining the water 

 level by trying the water gauge cocks. You can not 

 entirely rely upon glass gauges, floats, and water alarms. 



3. When starting the fire, open the upper water gauge 

 cock and do not close it until steam begins to issue from 

 it. This permits the escape of confined air. 



4. Kindle the fire on a thin layer of coal to protect 

 the gra'te bars. 



5. Always examine the safety valve before starting a 

 fire. 



6. When starting the fire all drafts should be open. 



