258 THE LIFE OF A BIRD. 



most successfully carried on. It was kept a great 

 secret, not only from strangers, but even from the 

 residents in other parts of the same country. The 

 buildings in which this process was carried on 

 were open to the inspection of observers ; but the 

 secret lay in the regulation of their temperature, 

 a point, the ignorance of which could only lead 

 any experimenter on a similar method to certain 

 failure. Their plan was as follows : 



An oven of bricks was constructed about nine 

 feet high. The middle is formed into a gallery 

 about three feet wide and eight feet high, extend- 

 ing from one end of the building to the other. 

 This gallery forms the entrance to the oven, and 

 commands its whole extent, facilitating the various 

 operations indispensable for keeping the eggs at a 

 proper degree of warmth. On each side of this 

 gallery there is a double row of rooms, every room 

 on the ground-floor having one over it of precisely 

 the same dimensions. These have a round hole for 

 an entrance of about a foot and a half in diameter, 

 wide enough for a man to creep through ; and into 

 each are put four or five thousand eggs. The 

 building is adapted for hatching from forty to 

 eighty thousand eggs, which are laid upon a mat 



