346 ARTIFICIAL INCUBATION 
the sand tray or other device for moisture should be removed, and 
the nursery tray placed in proper position. The wire in front of 
the egg trays should be opened, and the tray placed with this 
opening in front, so that, when the chicks are attracted to the 
front by the light, they will fall down into the nursery. In most 
machines it is well to cover the glass with a cloth or burlap during 
the hatching. This keeps the chicks more contented and prevents 
crowding, and when the burlap or cloth is removed they are 
stronger and better able to protect themselves. 
If the hatch has been properly conducted, it should start about 
the nineteenth or twentieth day after the eggs were placed in the 
machine, and all chicks which are to hatch will probably be out 
at the beginning of the twenty-first or twenty-second day. This, 
however, will vary somewhat with the temperature at which the 
machine has been operated and with the character or type of eggs 
set. The higher the temperature the earlier the hatch will start; 
large brown-shelled eggs from the heavy breeds require from one- 
half day to a day longer than the thinner-shelled eggs from the 
lighter breeds. The one important thing at this time is that the 
hatch should be uniform and complete soon after the first pipping. 
A prolonged hatch is rarely a successful one. If a hatch does 
not turn out properly, it is well for the operator to look over the 
records and see if he is at fault. The chicks should be left in the 
machine from twenty-four to thirty-six hours after all are hatched. 
As soon as the hatch is complete, the egg tray should be removed, 
and a little fine grit and oatmeal be thrown into the nursery; this 
will stimulate the digestive system of the chicks and teach them 
_ to pick up feed. It is rarely of any use to remove from the shell 
chicks which are incapable of getting out themselves. 
Poor hatches may be due to various causes, such as poor eggs, 
faulty condition of the breeding stock, or want of care previous 
to putting in incubator. Given good eggs at the start, disappoint- 
ment is most often the result of inexperience and poor management 
of the machine, especially shown by irregularity in attendance 
and imperfect regulation of the ventilation and humidity. To 
operate an incubator successfully the attendant must make up his 
mind to put considerable thought and effort into the work and to 
perform the duties methodically. 
Another factor in low hatching is a poor thermometer. To 
prevent this, the accuracy of the thermometers should be tested 
at the beginning of each season by comparing them with a clinical 
