INCUBATION 91 



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 in- 

 cubators are heated by circulating hot water. Such 

 incubators 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, 

 electricity, 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 correct is stirred about in warm water until the 

 degree of heat is 105 F. or a little higher. Other 

 thermometers are then held in the same hand with 

 the one known to be correct and all are stirred about 

 in the water so that the reading of all may be taken 

 under like conditions. Any instruments that fail to 

 mark the temperature correctly are rejected. It is best 

 to test all thermometers in use at least once a season. 



The printed directions that come with each incubator, 

 giving instructions for its operation, also tell where 

 the thermometer is to be placed in the machine, and to 

 secure the best results such directions should be 

 followed to the letter. The thermometer is usually 

 placed in or near the center of the egg tray. 



