A rtificial Incubation. 1 7 7 



eggs are laid by the lion all that is needed, if they are fertile, 

 is to give the same amount of heat, air, and moisture as if 

 brooded by the mother, and the chickens must come. This 

 has not, however, been found so very easy in practice. In 

 the first place, the heat must be kept regular, like that of 

 the hen ; and, in order to obtain this, most elaborate and 

 ingenious machines have at various times been devised, the 

 object being, of course, to regulate the supply of heat, so 

 that the temperature to which the eggs are subjected might 

 be maintained as evenly as possible. Many of these worked 

 splendidly, so long as the mechanism did not get out of 

 order ; but this mechanism was necessarily so intricate, that 

 very little upset it, and, in addition to this, the cost was so 

 great that only the wealthy could afford to risk so much money 

 over a doubtful experiment. In other machines, where the 

 regulating power was not so susceptible, all went well so long 

 as the outer atmosphere was moderately even, but, as soon 

 as a sudden change came, the calculations were upset, 

 and the eggs chilled or roasted. A hen's body is always 

 about the same in heat, and she sits closely or lightly, in 

 accordance with the weather ; but, as a machine can never 

 be made to think, and cannot be endowed with instinct, pre- 

 parations are necessary to meet all conditions, and these 

 preparations, in many instances, meant complexity and expen- 

 siveness. The accounts of the egg ovens of Egypt, China, 

 and Siam, where artificial egg hatching has existed for 

 centuries, led many to attempt reaching the' same end here, 

 and the records of the Patent Office, show the large numbej 

 of attempts made to find success, many of which exhibited 

 very great skill and scientific knowledge. It was forgotten, 

 however, that what was possible and easy in the countries 

 we have named, where the temperature is high and very even, 

 is most difficult in an erratic and cold climate. Even with 

 natural hatching, the difficulties in the way, are greater in 



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