496 A STUDY OF FARM ANIMALS 



determine the temperature at which the incubator should 

 be operated. The thermometer may be arranged so that 

 the bulb is in contact with the eggs or it may be hung above 

 the eggs so that the bulb does not touch the top of the eggs. 

 These two methods would each require a different reading 

 to produce the correct temperature of the contents of the 

 egg. When the bulb of the thermometer is in contact with 

 one or two eggs and is on a level with the upper one fourth 

 of the egg, the temperature should be 102 the first week, 

 103 the second week, and 104 the third week. If the 

 thermometer is hung so that the bottom of the bulb rests on 

 the top of the egg, the readings should be 103 the first week, 

 104 the second week, and 104^ the third week. With 

 the thermometer suspended just above the eggs so that the 

 tray can be removed without striking the thermometer, the 

 temperature should be 103 the first week, 104 the second 

 week and 105 the third week. 



The incubator thermometer should be tested at the be- 

 ginning of each season by comparing the readings with those 

 of a certified standard thermometer in warm water at 102, 

 103, 104 and 105 F, and careful note made of all variations. 



Moisture and ventilation in the incubator are so closely 

 associated that they can not be considered separately. 

 Nearly all incubators have some provision for supplying 

 moisture during incubation. The use of moisture permits 

 greater ventilation during incubation without excessive evap- 

 oration of the egg contents. The amount of ventilation will 

 have a decided influence upon the quality and number of 

 chicks hatched. The greatest amount of oxygen is needed 

 from the 7th to the 20th day of incubation. The air in the 

 incubator should always smell sweet. If it has any per- 

 ceptible odor, there is not sufficient ventilation, and the eggs 

 will not hatch as they should. The safest method of supply- 

 ing moisture is by means of moisture pans located under 

 the egg trays. The question of ventilation is automatically 



