296 AX EGG FARM. 



side of incubator, the gas is not, and portions of the poi- 

 son will at once begin to move from the inside to the 

 outside and their places will be taken by constituents of 

 the air which will move from the outside to the inside, 

 even in the absence of any draft whatever such as differ- 

 ence in temperature creates, and this process will go on 

 until the air inside holds exactly the same per cent of 

 poison as the air in the cellar. We are supposing, of 

 course, that no more of the poison was formed within 

 the eggs and exhaled meanwhile. 



The above illustration shows what is meant by the 

 miscibility of gases, If the carbon dioxide keeps com- 

 ing from the embryo, as it will, then nature will keep 

 removing it, independent of air circulation created by 

 heat, if there are exits. The poison from the eggs under 

 the hen is bound to escape through the millions of inter- 

 stices in the downy portions of her feathers, no matter 

 if these enfold her nest so closely in cold weather that 

 the frictional resistance keeps the air from passing 

 through. This wonderful law of diffusion sets inertia, 

 gravity and friction at defiance, being more potent than 

 they. 



Manufacturers of the best modern incubators take a 

 leaf out of nature's book, and, avoiding upward ventila- 

 tion, make the egg chamber perfectly air-tight at top and 

 sides. The purchaser should correct shrinkage of mate- 

 rial at door and doorway, if any occur after the heat has 

 had time to take effect, so that the door shall shut 

 closely. The manufacturer also bores a set 01 small 

 holes through the bottom of the egg chamber, these 

 being furnished with buttons which may be turned over 

 them as desired. These holes permit the escape of the 

 poisonous carbon dioxide. This escape will be slow, but 

 constant, and the excessive drying out of the e^rgs, 

 which a current of air would cause, is avoided. For an 

 incubator of this sort, perfectly air-tight at top and sides, 



