AA are inlets for conducting hot air into the 

 heater S through pipes BB. When E is opened, 

 it allows the hot air to pass up AA and CC, 

 through D, and out at E, making a draft which 

 draws hot air out of the heater S at BB, at the 

 same time drawing cold air into the heater S at 



mi. 



D is a discharge pipe of double the capacity of 

 C, and carries off hot air from CC out at E when 

 E is open. 



E is the main outlet for hot air, S is the hot air 

 heater five inches deep. 



FIG. 4. 



H is the egg chamber. 



Ill I are tubes running through the top of heater 

 S, through which cold air is drawn into heater S, 

 when E is open. 



K is a thermostat in the egg chamber and is on a 

 level with the eggs. 



L is a metal rod connecting the thermostat with 

 the lever M. 



J is a ball or cover suspended at the outer end of 

 the lever M, and is made to open or close the out- 

 let E by action of the thermostat K. 

 88 



