Incubation and Incubators 191 



most or toward the outer side of the nest. This 

 is probably due to the form of the nest and the 

 fact that the small end of the egg is heavier in 

 proportion to its size than the large end; that 

 is, the center of gravity approaches the small 

 end, which is, as incubation progresses, due to 

 the development of the air-chamber in the large 

 end. The fact that the eggs are arranged with 

 the large end uppermost, has led some persons 

 to place the eggs in the incubator trays in a 

 similar position. Without doubt, the position of 

 the eggs does not have any particular influence 

 on the hatching. 



Many tests have been made to determine the 

 actual temperature of eggs when natural incu- 

 bation is taking place. These tests show a con- 

 siderable variation until the ninth or tenth day. 

 Until this time the eggs seldom reach 100.* 

 Although the temperature of the fowl is usually 

 above 106, yet the temperature of the eggs is 

 seldom raised above 103, owing to the fact that 

 heat is applied only on one side. 



Selection of an incubator. An inexperienced 

 person should exercise the same care and judg- 

 ment in selecting an incubator that would be 

 exercised when purchasing a mowing machine or 

 other expensive implement. It is no longer 

 thought that one particular kind of mowing 



*" Incubation and Its Natural Laws," Cyphers. 



