THE INCUBATION OF THE EGG 217 



there was an average difference in weight at July 1 of but 

 1.17 pounds. The younger chicks were not able to make 

 proper gains until the cool weather of the fall came. At 

 three and a half months the late-hatched chicks did not 

 weigh as much as the early-hatched ones did at three months. 



Mairs^ also found that early-hatched chicks grew faster 

 than late-hatched ones, and suggested April 1 as a suitable 

 hatching date for Pennsylvania without making any differ- 

 ence for different classes of chickens. 



Where the falls are quite late, judgment must be used in 

 selecting the date of hatching. It is entirely possible to hatch 

 out pullets so early that they will go through a general molt 

 in the fall, precisely as do the hens, and quit laying until 

 along toward spring. 



Routine of Management. — ^The practical application of the 

 principles of incubation will vary under different conditions 

 and in different locations. The routine of management 

 suggested hereafter has been found satisfactory in three 

 west-central states lying in the heart of the heavy poultry 

 producing section. 



Levelling the Machine. — ^The incubator should be made 

 level so that there will be no high, hot corners. This may 

 be accomplished by the use of a carpenter's level, taking 

 care to see that it is level from front to back as well as from 

 side to side. 



Disinfection. — If the incubator has been used before, during 

 the same or previous season, the egg chamber and nursery 

 should be very thoroughly disinfected, including the trays, 

 thermometer, and moisture pans. Disease that did no special 

 harm among chicks of a previous hatch may assume the 

 proportions of an epidemic in a subsequent one. A 3 per 

 cent, solution of any of the standard coal-tar stock dips will 

 be found satisfactory for this purpose. It is not necessary 

 for the machine to be dried out before putting in the eggs, 

 provided the proper temperature has been reached. 



Preparing the Lamp. — ^The lamp should not be filled above 

 a point a half-inch from the top. In a lamp that is too full 



' Pennsylvania Bulletin No. 87. 



