ARTIFICIAL HATCHING 123 



in size from those with a capacity of 60 eggs to those as high 

 as 460 eggs. They are generally heated by kerosene lamps, 

 but, when available, gas is more profitable. The small 60- 

 egg incubator is especially adapted to the use of the poultry- 

 man who hatches only from one to two himdred eggs, and 

 also to the pupil who must begin in a small way, and get 

 his experience before trying any of the larger types. Mam- 



Fia. 68. — An individual incubator which has a capacity of 240 eggs and ia heated 

 by a kerosene lamp. 



moth incubators have come on the market but recently. 

 They are intended for use on large farms where thousands 

 of eggs are hatched every spring, and range in size from 1,500 

 to 30,000 egg capacity. Heat is generated either by coal or 

 gas. Burning coal heats hot water which circulates in pipes 

 above the eggs. In most of these mammoth machines, the 

 heat is regulated by the expansion and contraction of the 

 water in the heating system. Slight variations in tempera- 

 ture are met by raising or lowering the egg trays, or by 

 allowing the hot air to escape through a perfectly controlled 

 regulator or ventilator. 



In selecting an incubator for home use, the individual 

 machine will probably be the best, and the one selected 

 should bear a good reputation, and be well built and durable, 

 with an egg capacity of from 60 to 220 eggs. In choosing 

 a particular make of machine it is safe to purchase one of 



