To be sure that the incubator fixtures are plumb, use a spirit level, the only safe guide. After starting the machine, practise running it for a few days before putting in the eggs. When the heat reaches one hundred and two and one-half degrees, with the escape dial hanging the width of a match from the opening, put in the trays, which, being cold, will lower the heat, and should close the dial until the trays become warm, and the thermometer in the machine again registers one hundred and two and one-half, when the dial should once more be dangling the match width above the opening. Should the closing and opening not take place as the heat varies, the machine is not properly adjusted, and you must practise until it will bear the test before putting in the eggs. The thermometers are supposed to have been tested before they are shipped, but it is well to buy an extra one and compare them; or get your doctor, who is sure to have an accurate thermometer, to do it for you. The egg tester comes with the incubator. It is a tin, funnel-like chimney that fits over the lamp, and has a projecting opening, bordered with black, before which to hold the eggs. The first test should be made on the seventh day; the second on the fifteenth day. Hold the egg, large end uppermost, in front of the opening. If it looks perfectly clear it is infertile and can be used to feed young chicks. If it shows a dark-red spot with spidery legs it is fertile, and must be returned to the incubator. Dead germs are rarely discernible at the first testing, except to the expert eye. By the fifteenth, the veriest amateur will be able to detect them. Successful incubation depends principally on being able to maintain the amount of heat and moisture necessary at the different stages of development. A thermometer is furnished with most incubators, but as yet hygrometers are not, so it is advisable to buy one. For as they only cost $1.50 each, it would be pennywise and pound-foolish to do without one. Having these two little instruments to tell exactly the amount of heat and moisture present in the machine, simplifies the work wonderfully. Personally, I like to have the thermometer register 102 degrees, and the hygrometer 75, when I first put the eggs in the incubator. The second week, the heat is increased to 102½, and the moisture lowered to 70 degrees. The third week, heat from 102½ to 103; moisture not over 45 until the nineteenth day, when the moisture is again increased to 55 or 60 degrees.