Incubation. — Part I 



n77 



The thermostat is a most important part of an incubator. The hatch- 

 ing qualities of a machine depend largely on the sensitiveness and power 



Fig. 19. — A common type of regulating device with the parts properly connected 



of the thermostat. As the heat expands the thermostat, the latter, if 

 it is properly connected, pulls down on the connecting rod that is fastened 

 to the regulator bar by the thumb screw, raising the disc that is hooked 

 to the end of the regulator bar over the heater and thus allowing the 

 surplus heat to es- 

 cape. As the heat 

 is lowered the ther- 

 mostat contracts, 

 allowing the disc to 

 drop down on the 

 heater. The ther- 

 mostat is usually in 

 place when the in- 

 cubator comes from 

 the factory, but if 

 found loose or detached little difficulty should be found in screwing it in place. 

 There are several styles of thermostats now on the market, as seen in 

 Fig. 20. This illustration shows (i) the six-bar type; (2) the double-disc; 

 (3) the single-disc; (4) the three-bar type. The style most commonly 



used is composed of 

 three metal bars, usu- 

 ally a bar of steel be- 

 tween two bars of 

 zinc. These bars are 

 riveted together at 

 both ends and expand in the center when heated ; therefore the connecting 

 rod is passed through the bars at this point and fastened to the lowest. 



Fig. 20. — Several styles of thermostats 



Fig. 21. — Four-bar thermostat 



