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
Fig. 145. Typewriter, L. C. Smith.
256. Construction of Typewriter. The typewriter is a machine for printing letters (Fig. 145). The letters making the imprint are attached to shafts which can each swing to one point. Care should be taken to strike one key at a time, as they are all made to reach the same point, and contact with each other may cause bent shafts. If a shaft becomes bent, the letter attached to it will not swing to the desired point, so will be out of alignment, or will fail to leave a mark, since the imprint is made on a roller and the letter hits only the nearest part of the surface. The shaft may have one, two or three letters on it. This is made possible by the use of the shift key which raises or lowers the framework to which the roller is attached, so that when the machine is in normal position, one set of type on the keys will be imprinted, and, upon the holding down of a shift key and simultaneously striking a letter, another set of type will make the imprint. On some typewriters there are two shift keys, allowing three sets of characters to be used. The motion of the keys turns a small wheel which shoves the roller from right to left, and, also, turns the spools of ribbons so that a new bit of ribbon comes under the letter each time a key is struck. If the ribbon did not move, the letters would soon cut a hole thru it. This ribbon carries the ink which reproduces the imprint of the letter. When the end of a ribbon is reached, most machines reverse its direction so that it again winds onto the spool from which it has just unwound. On other machines, it is necessary to release the bar which controls the spools to reverse the winding of the ribbon.