

HEAT AT THE TOP. 275 



the egg, to which the very construction of the 

 egg seems to indicate that its quickening influ- 

 ence must be applied. In effecting this end the 

 waterproof cloth with its warm contents, or the 

 harder surface of glass, is the representative 

 of the mother's breast ; and by the construction of 

 the machine the egg derives its first supply of 

 heat exclusively from above, just as in nature, 

 some time necessarily elapsing before the warmth 

 is conducted to the lower part of the egg, and the 

 warmest part being always at the top nearest the 

 warm water. There can be no question that by 

 this means a smaller amount of evaporation takes 

 place from the egg, than would be the case under 

 other circumstances, and particularly than is the 

 case in other systems of artificial incubation in 

 which the whole surface of the egg is exposed 

 to the action of heat. 



The temperature employed in the " top-contact" 

 incubation is considerably higher than is usual in 

 artificial incubation upon other plans. The tem- 

 perature of the water is about 109 Fahrenheit, 

 which ensures a temperature of about 106 to the 

 surface of the eggs, This temperature has been 

 found to be nearly that of the blood-heat of the 



