The case of the incubator should be built double, or triple-walled, to withstand variation in the outside temperature.  The doors should fit neatly and be made of double glass.  The lamp should be made of the best material, and the wick of sufficient width that the temperature may be maintained with a low blaze.  The most satisfactory place for the lamp is at the end of the machine, outside the case.

Regulators composed of two metals, such as aluminum and steel, are best.  Wafers filled with ether or similar liquid are more sensitive but weaker in action.  Hard-rubber bars are frequently used.

The most practical system of controlling evaporation is a system of forced ventilation, in which the air is heated around the lamp-flue and passes through the egg-chamber at a rate determined by ventilators in the bottom of the machine.  With the outside air cold and dry only slight current is required, but as the outer air becomes warmer or damper more circulation is needed.

Turning the egg is not the work that many imagine it to be.  It is not necessary that the egg be turned with absolute precision and regularity.  An elaborate device for this work is useless.  The trays will need frequently to be removed and turned around or shifted, and the eggs can be turned at this time by lifting out a few on one side of the tray and rolling the others over.

Two other points to be considered in the incubator are:  A suitable nursery or place for the newly hatched chick, and a good thermometer.

Rearing Chicks.

If it is very early in the spring, and the ground is damp, it is best to put the hen and her brood in some building.  During the most of the season the best thing is an outdoor coop.  The first consideration in making a chicken-coop is to see that it is rain-proof and rat-tight.  The next thing to look for is that the coop is not air-tight.  Let the front be of rat-tight netting or heavy screen.  The same general plan may be used for small coops for hens, or for larger coops to be used as colony-houses for growing chickens.  The essentials are:  A movable floor raided on cleats, a sliding front covered with rat-tight netting, and a hood over the front to keep the rain from beating in.  If used late in the fall or early in the spring a piece of cloth should be tacked on the sliding front.

The chicken-coops should not be bunched up, but scattered out over as much ground as is convenient.  Neither should they remain long in one spot, but should be shifted a few feet each day.  At first water should be provided at each coop, but as the chickens grow older they may be required to come to a few central water pans.

As before suggested, rearing chicks with hens is the only suitable method for general farm practice.  The brooder on the farm is an expensive nuisance.