Start the incubator with a good, clear, high flame in the lamp, so that it can be turned lower as the germs in the eggs begin to grow and generate heat. Start the incubator at 100 degrees Fahrenheit, and by the second day, it will reach the temperature of 102 degrees. [Illustration: FIG. 143. Egg tester.] Violent fluctuations of temperature in the incubator are dangerous and should be avoided. Accuracy in reading temperatures and in adjusting the thermostat and ventilators is essential. Fill the lamp and turn the eggs regularly. Cleanliness is important. Disinfect the incubator between hatches, and air it well. Cresol soap and water make a good disinfectant for incubators. Turn and handle eggs with clean hands. To know whether the incubator has the proper amount of moisture supplied, weigh the trays before filling, weigh after filling. At the end of the fifth day, weigh tray and eggs again, subtract the tray weight, which is constant, from the weight of the whole, and note the difference between this weight and the original weight of the eggs. If 100 eggs have lost 8.38 ounces, or 4.17 per cent of their weight, the moisture is correct. [Illustration: FIG. 144. Appearance of eggs when put in egg tester.] If they have lost too much weight, give more moisture or less ventilation, but, remember, that pure air is essential to incubators, so do not shut off ventilation entirely. If not enough weight is lost, open the ventilators, and, if necessary, for the next hatch, place the incubator in a drier place. =255. Egg Tester.= An egg tester is a device for looking thru eggs to ascertain whether or not they are good. It consists of some device to keep all bright light away from the eyes except a few bright rays shining thru the egg. The hole should be about an inch long and three-fourths of an inch wide. A metal chimney with one such opening in the side used in a darkened room serves as an egg tester. A large piece of cardboard tacked over a sunny basement window is sometimes used, the hole being cut in the cardboard (Fig. 143). Hold the egg between the finger and thumb before the opening. Look at the egg as the light shines thru it. Fig. 144 shows how good and bad eggs look when viewed in egg tester. CHAPTER XXXVI TYPEWRITERS [Illustration: FIG. 145. Typewriter, L. C. Smith.]