INCUBATTOX ;, 391 



chamber that can be held' at tne* required ' temperature. 

 Incubators are also supplied with thermometers and 

 means of ventilation. 



In the various incubators heat is brought into contact 

 with the eggs either by diffusion or radiation. In 

 diffusion incubators, hot air is evenly distributed through- 

 out the egg chamber. In radiation incubators, the heat is 

 radiated from pipes or radiators that are heated either 

 by hot air or by hot water. A large part of the incuba- 

 tors in use are of the diffusion type, in which the air is 

 heated by an oil lamp. In these machines the heated 

 air passes directly into the egg chamber and throughout 

 the interior of the machine. The eggs in the tray are 

 thus surrounded with air at the required temperature. 

 Incubators in which the heat is both radiated and 

 diffused are also used. The more evenly the egg chamber 

 is warmed the greater will be the success in hatching. 



The most satisfactory source of heat for incubators of 

 all kinds is that obtained from oil lamps. Some incuba- 

 tors are heated by circulating hot water. Some incu- 

 bators require particular care and attention, and their 

 efficiency depends on the proper circulation of the water, 

 the distribution of the pipes, and the lasting qualities 

 of the entire heating system. Illuminating gas, elec- 

 tricity, and alcohol lamps are also used to some extent 

 as sources of heat for incubators. 



Incubator manufacturers prefer thermometers specially 

 made to suit each kind of machine. There is usually 

 a reason for such preference, and the thermometer 

 recommended by the manufacturers should be favored. 

 If this instrument cannot be obtained, the best that is 

 made must be selected. Incubator thermometers are 

 scaled from 90 F. to 110 F., and are marked low at 

 100 F. and high at 105 F., and the scale is crossed at 

 103 F. by an arrow or a heavy line. It is thus easy to 

 make an accurate reading between the low and the high 

 marks, provided the thermometer is correctly graduated. 



Before being used, incubator thermometers are tested 

 in the following manner: An instrument known to be 



