248 



COMMERCIAL POULTRY RAISING 



expedient to turn the lamp out completely, sometimes for several 

 hours, re-lighting it again toward evening. 



Always test an incubator before filling it with eggs. This ad- 

 vice applies to both old and new machines. A few hours spent 

 in adjustment will be time and money saved later on, perhaps. 



Just because a machine 

 worked satisfactorily the last 

 time it was used the preceding 

 season, is no guarantee that it 

 has remained in perfect adjust- 

 ment. During the six months 

 or more in which it was idle a 

 great many things could hap- 

 pen to it. Dust or dirt may 

 ha\'e clogged some of the parts, 

 dampness may have caused 

 swelling or warping, a child, 

 stray fowl, cat, rat or mouse 

 may have interfered with the 

 regulator or some other vital 

 part. 



Heat Control. — It is impos- 

 sible, of course, to attempt to 

 explain the individual peculi- 

 arities of the heating devices 

 of different makes of machines. 

 The card or book of directions 

 which accompanies the incu- 

 bator should be followed for 

 this advice. The general principle, however, is the same in all 

 machines. Inside the egg chamber there is a thermostat, an instru- 

 ment made of a combination of metals, such as steel, zinc ajid 

 aluminum, which contract and expand, and thereby operate a 

 damper. Wafer or disc thermostats, which contain some fluid used 

 for expanding the disc, are also used. The point is this, they are 

 connected by a thin rod to a bar or regulating arm, which is 



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(Courtesy Prairie Slate l7icubator Company) 



Fig. 157. — Diagram of an incubator 

 heater and lamp. 



