34 %* Machine as a Mother. 



warmed, and either afford a copious supply of moisture, or pro- 

 vide the air with what they suppose to be the proper amount 

 of moisture, which they endeavor to regulate with water-pans, 

 the humidity being indicated by a moisture-gauge; but it is a 

 matter for discussion whether air and moisture are required at 

 all times, and whether these apparent essentials depend upon 

 the seasons and the humidity of the atmosphere the location 

 of the incubator more or less affecting the result. 



Artificial incubation has 6een but an attempt to imitate 

 the hen. We know that a temperature of 103 degrees Fahren. 

 heit is required for the period of three weeks, and we know 

 that the hen changes the position of her eggs, and in so doing 

 she turns them, but we know nothing of how she supplies air 

 and moisture, if, in fact, she supplies either. That all the 

 eggs are not kept at a temperature of 103 degrees the whole of 

 the time is known by the hen exposing them, in rotation, to a 

 less warmth than when they are in the center of the nest ; but 

 she never voluntarily cools them unless driven off the nest by 

 the animal heat of the chicks in the eggs, or in order to feed. 



At all periods of incubation the hen carefully guards the 

 eggs against currents of air. No draughts flow constantly 

 across them, and she never imparts moisture at any time. 

 The eggs are provided with a sufficiency of moisture natur- 

 ally. Experiments made with eggs from the hen and the 

 duck, in a comparison and test with eggs of both, in incuba- 

 tors and under hens, show that the first process in the disposal 

 of moisture is not to secure it but to get rid of it by evapora- 

 tion ; the air sacs at the large ends of the eggs enlarging more 

 rapidly under hens than in the incubators, and the eggs of 

 the duck evaporating their contents of moisture more rapidly 

 than the eggs of the hen. These facts lead us to suppose that, 

 as the air in the nest of a sitting hen is still (not circulating 

 in currents) and the nest is dry, there is no room for thought in 

 the matter of supplying eggs with currents of air, laden with 

 moisture, in incubators. Too much moisture and warmth not 

 only prevents the creation of space in the egg for the growth 



