430 



THE ESSENTIALS OF AGRICULTURE 



568. Incubating. The germ spot on the yolk of an egg is 

 always at the uppermost point. If an egg is turned, the yolk 

 will slowly rotate inside the shell until the germ comes to the 

 highest point. This serves to bring the germ, which develops 

 into a living chick, near to the warm body of the sitting hen. 



A fertile egg will develop into a chick in twenty to twenty- 

 one days if the temperature at the level of the top of the egg is 



kept at 103 degrees F. 

 The temperature of the 

 hen's body is usually 

 1 06 degrees F., and the 

 top of the egg will gen- 

 erally be found to be 

 about 103 degrees F. 



It has been found that 

 by furnishing the same 

 temperature by artificial 

 means, eggs may be 

 successfully hatched. 



^fjp^' Boxes (called incuba- 



tors), heated by an oil 

 lamp with an automatic 

 damper that opens to 

 FIG. 221. Black Orpington hen allow the escape of heat 



A popular representative of the English class if it is tOO high, Or closes 



to hold more heat in the 

 box when it is too low, are used very successfully for hatching eggs. 



569. Managing an incubator. The incubator should be kept 

 in a room where the temperature is fairly uniform. For this 

 reason a cellar is often used, being found more satisfactory than 

 a living room, which is likely to be too cool at night. Care 

 must be taken to see that the top of the incubator is level, so 

 that the heat will be evenly distributed. 



After the lamp has been lighted, the regulator should be 

 adjusted until an even temperature of 102 degrees F. or 103 

 degrees F. is maintained at the level of the top of the eggs. 



