The reason for such fluctuation in the moisture may need some explanation. During the first stages of incubation it is necessary to prevent the escape of the water which is part of the egg, as it is needed to keep the albumen in the right condition for the development of the germ. After the tenth day, when the embryo is formed, the water should be gradually allowed to evaporate, so that the amount of air inside the shell increases, as it is needed to aid the circulation of the blood and permit the growth of the chick. Increasing the moisture again on the nineteenth day is simply done to soften the inside skin of the egg and make it easy for the chick to break through. When extra moisture is to be supplied, place a pan of wet sand or a damp sponge in the bottom of the incubator. If the machine is standing in a very damp cellar, the difficulty is often to keep down the moisture rather than to increase it. In this case, keep the trays out of the machine for a greater length of time when you turn the eggs each day, and open the ventilators. Probably the safest and simplest way to learn how to gauge this important point of moisture, is to set a hen at the same time that you start the incubator, and then compare the development of the air-cell in the egg every few days. If the development is too slow, open the ventilators at the side of the incubator wider, and air the eggs a little longer each day when you have the trays out to turn the eggs. Reverse affairs if the development is too quick. It is better to run the machine a degree or two above the given temperature than below it, especially during the last few days. After the morning of the twentieth day don’t open the incubator until the hatch is over, or until late on the twenty-second day, and don’t get nervous if the temperature runs to one hundred and four or even to one hundred and five; it is caused by the animal heat of the chicks, and will do them no harm. Turning down the lamp slightly will of course reduce the heat; but be very careful not to let it run below one hundred and three during the last twenty-four hours. Low temperature prolongs the hatch, weakens the chickens and makes them susceptible to all sorts of ailments.