332 ARTIFICIAL INCUBATION 



and spoiling the eggs. A strongly built copper tank, with proper 

 care, should last many years, but a thin copper or tin tank can- 

 not be expected to last longer than two or three seasons. Sedi- 

 ment soon forms in the bottom of the tank, especially if hard 

 water be used. The tank is hard to clean, and this sediment 

 accumulates in different parts of the circuit and causes uneven radi- 

 ation, with variation in the temperature of the different parts of the 

 machine. Hot-water machines will hold the heat longer than the 

 hot-air type; they have the advantage that when, for any reason, 

 the lamp goes out in the night, there is less danger of an incubator 

 cooling down to a dangerous degree before it is discovered. 



FIG. 158. Modern mammoth incubators. A, Phantom view showing arrangement 

 of pipes and circulation of water; B, another make of incubator with brooders below. (Pho- 

 tos, A, Hall Mammoth Incubator Co.; B, Candee Incubator Co.) 



The hot-air incubators seem to be the most popular, no doubt 

 because they require less attention, are cheaper, less complicated, 

 and less liable to get out of repair. There are a number of excellent 

 hot-water incubators on the market, but, all things considered, 

 the hot-air type is the safest and best. 



Incubators, according to their size and type, are also classified 

 as individual, or small, and mammoth incubators. The small 

 ones are composed of single compartments for the eggs, with 

 capacities of fifty to five hundred, each unit being a separate 

 machine heated by its own lamp. The mammoth incubator con- 

 sists of multiple units a number of egg chambers the entire 

 machine having a capacity of from two thousand to fifteen or 

 twenty thousand eggs, heat being generated in a central heating 

 plant or boiler, and conveyed to all the compartments by means 

 of hot-water pipes extending above the egg trays (Fig. 158). 



