198 POULTRY PRODUCTION 



it is poured into a metal drum occupying the heating chamber, 

 from which it radiates downward. If water is the medium 

 it may circulate in a tank or drum, or it may pass through 

 pipes (see Figs. 94 and 95). In either case the heat is given 

 off from the container by radiation. 



In the combination method (see Figs. 93 and 99) air is 

 heated and poured into the rather restricted heating chamber, 

 from whence it heats the egg chamber by radiation through 

 metal sheets at the bottom of the heating chamber and by 

 escaping into the egg chamber through openings arranged 

 for that purpose. 



The contact method of heating is based on the assimiption 

 that heating the eggs, as the hen's body does, by actual 

 contact, is more eflBcient than by simply placing them in 

 a warm chamber. This has usually been attempted by pour- 

 ing the heated air or water into a rubber bag that was laid 

 on the eggs, or by bringing the eggs in contact with a 

 drum heated to the proper temperature. Insurmountable 

 difficulties, mostly mechanical, have so far prevented the 

 manufacture of a successful machine heated on this principle. 



Air Heaters. — ^An excellent type of air heater is shown in 

 Fig. 100. The flame from a kerosene lamp burns at the bottom 

 of the direct heat flue (8) . The fumes pass through the open- 

 ing (4) connecting the direct heat flue (8) with the escape 

 flue (7) and out into the room. 



Fresh air enters opening (13) to the fresh-air chamber (6), 

 where it is heated by contact with the outer surface of the 

 direct heat flue (8) and the inner surface of the escape flue (7) . 

 After being heated in the fresh-air chamber (6) it passes into 

 the heating chamber through an opening (2) near the top 

 of the chamber. In case of excessive heat in the egg chamber 

 the regulator raises the damper disk (20) and allows the 

 heated air to escape through the opening (9) at the top of 

 the chamber, instead of passing into the machine through 

 the lower opening (2). 



Water Heaters. — ^There are two methods of heating the 

 water for hot-water machines. The first is to surround 

 the heater with a water jacket which communicates with the 

 tank, as shown in Fig. 95. The second is to heat air which is 



