In =placing the high-power objective in position=, it is first necessary to raise the body by the coarse adjustment; then open the iris diaphragm, and lower the body until the objective is within about one-eighth of an inch of the slide. Now raise the tube by the fine adjustment until the object is in focus, then gradually close the iris diaphragm until a clear definition of the object is obtained. Now proceed to make an accurate sketch of the object or objects being studied. In =using the water or oil-immersion objectives= it is first necessary to place a drop of distilled water or oil, as the case may be, immediately over the specimen, then lower the body by the coarse adjustment until the lens of the objective touches the water or the oil. Raise the tube, regulate the light by the iris diaphragm, and proceed as if the high-power objectives were in position. The water or oil should be removed from the objectives and from the slide when not in use. After the higher-powered objective has been used, the body should be raised, and the low-power objective placed in position. If the draw-tube has been drawn out during the examination of the object, replace it, but be sure to hold one hand on the nose-piece so as to prevent scratching the objective and Abbé condenser by their coming in forceful contact. Lastly, clean the mirror with a soft piece of linen. In returning the microscope to its case, or to the shelf, grasp the limb, or the pillar, firmly and carry as nearly vertical as possible in order not to dislodge the eye-piece. ILLUMINATION The illumination for microscopic work may be from natural or artificial sources. [Illustration: FIG. 30.--Micro Lamp]