Fig. 24.—Micrometer Eye-Piece
MICROMETER EYE-PIECES
Micrometer eye-pieces (Figs. 23 and 24) may be used in making measurements. These eye-pieces with micrometer combinations are preferred by some workers, but the ocular micrometer will meet the needs of the average worker.
MECHANICAL STAGES
Moving objects by hand is tiresome and unsatisfactory, first, because of the possibility of losing sight of the object under observation, and secondly, because the field cannot be covered so systematically as when a mechanical stage is used for moving slides.
The mechanical stage (Fig. 25) is fastened to the stage by a screw. The slide is held by two clamps. There is a rack and pinion for moving the slide to left or right, and another rack and pinion for moving the slide forward and backward.
Fig. 25. Mechanical Stage Fig. 26.—Camera Lucida
CAMERA LUCIDA
The camera lucida is an optical mechanical device for aiding the worker in making drawings of microscopic objects. The instrument is particularly necessary in research work where it is desirable to reproduce an object in all its details. In fact, all reproductions illustrating original work should be made by means of the camera lucida or by microphotography.