BOILER AND MANAGEMENT * 331 
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. 
GENERAL 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 grate bars. 
5. Always examine the safety valve before starting a 
fire. 
6. When starting the fire all drafts should be open. 
