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POULTRY BREEDING AND MANAGEMENT 



eggs. In the former, the hot water tank heats air already 

 in the egg chamber ; in the latter, fresh air is heated by the 

 lamp as it enters the machine and the same air enters the 

 egg chamber by diffusion. So that there is the diffusion 

 type of machine and the radiated heat type. In the latter 

 the ventilation is independent of the source of heat. It 



A 250-EGG INCUBATOR, KEROSENE LAMP HEATED 



requires longer to heat up the hot water machine than the 

 hot air. 



On the other hand, the former maintains the heat longer, 

 and this is an advantage in case the lamp goes out. To 

 secure the same ventilation, or the same rate of exchange of 

 air in the hot water machine as in the hot air, or the same 

 degree of air purity, there must be more openings for 

 ventilation in the former than in the latter. If the ventila- 

 tion be arranged, therefore, so that there may be the same 

 rate of exchange of air, or the same degree of air purity, 

 there should be little, if any, difference in efficiency due to 



