249. The Body of the Incubator. The box-like body of a good incubator is set on strong legs which raise it to a convenient height. The trays slide into the box on cleats about two or three inches from the bottom of the body. They fit so that a slit about two inches wide is left between for the chickens to drop down under the tray as they hatch. Usually this is near the door. If the door is furnished with a glass to admit light, the chickens are attracted toward light and fall thru the slit.
Fig. 140. Incubator.
The walls of the incubator are usually double so that air can be let in without making a draft. Dampers in the side of the machine regulate the admission of air. Ventilation both regulates the amount of air circulating in the incubator and the amount of moisture. Air from a damp room keeps the eggs moist. Air from a dry room dries them.
250. Incubators Heated by a Lamp. Choose a lamp which holds enough oil to last for twenty-four hours. Good lamps are usually made of metal and as plain as possible (Fig. 141).
Fig. 141. Incubator
lamp.
The burner furnished with them is an ordinary lamp burner carrying a straight, flat wick. Metal chimneys are used, there being enough mica in one side to permit the flame to be seen. The chimney extends into a metal chamber containing the hot-water pipes, or into a chamber thru which air is taken and heated by the chimney. The fumes from the burning oil pass out into the room and not into the incubator. The heated air passes thru ducts into the incubator. These are often constructed of wood.
251. The Wick. The wick most generally found practical is the cotton wick, such as is used in ordinary lamps. It should be kept clean and renewed often. The lamp should be kept filled regularly. The wick must always be kept trimmed even, to prevent smoking.
Incubators heated by electricity have the heating unit placed either above or below the trays of eggs. The current is controlled by a thermostat.