INCUBATION 371 



After the correct temperature is reached, the incubator should run 

 with only slight variations. Although it is best to maintain an even 

 temperature, it is not always possible to do so, and a variation of one- 

 half degree, or more, from time to time, will not result seriously if the 

 average temperature is correct. A high temperature should be avoided, 

 especially at the beginning of incubation. 



The temperature should be read through the glass door. The door 

 should be opened as little as possible. 



Temperature, first week. — The position of the thermometer should 

 always be considered in determining the proper temperature to main- 

 tain. If the thermometer hangs above the trays, as it does in some 

 machines, thereby registering the air temperature and not the tempera- 

 ture of the eggs, the actual temperature of the eggs would be from 

 one to one and a half degrees lower the first week than the registered 

 temperature. To give the eggs the proper amount of heat the first 

 week, where hanging thermometers are used, it is necessary to keep the 

 temperature at 1021° or 103°; whereas with contact thermometers, the 

 temperature should be 102°. Contact thermometers should always 

 be placed between two fertile eggs. 



Temperature, second week. — The outside temperature has less 

 influence over the machine temperature after the first week, owing 

 to the increasing amount of animal heat given off by the growing em- 

 bryos. Machines using a hanging thermometer should be held at 103° 

 F., while in those using contact thermometers, the heat should be 

 increased to 103° F. 



Temperature, third week. — Hold the temperature as near 103° 

 as possible up to about the eighteenth day, when it may be allowed to 

 run up to 104°. 



The eggs. — The eggs should not be put in the machine until 

 it has been run for several days properly regulated and all 

 directions have been followed out in regard to setting up, paying 

 special attention to the manufacturer's directions about ventilators, 

 felts, trays, etc. 



Incubate eggs of uniform size, shape, and color as far as possible, and 

 eliminate those with very porous or otherwise defective shells. 



Eggs from the heavy type of fowls usually take a few hours longer 

 to hatch than Leghorn eggs ; therefore it is not advisable to set the two 

 kinds of eggs together in an incubator. 



