ON MICROSCOPICAL EXAMINATION. xxvii 



the object on the stage under the objective, and carefully 

 lower the body with a screwing motion till the objective is 

 about a quarter of an inch from the cover-glass ; then look 

 through the eye-piece, and gradually raise the body till the 

 object becomes distinctly visible. Focus accurately with the 

 fine adjustment screw. With the high power, begin with the 

 objective close to the cover-glass, and then proceed as before. 



2. Never examine an object with the high power unless it 

 is protected by a cover-glass. Take extreme care never to let 

 the objective touch the cover-glass, and never to touch the 

 face of the objective or allow any dirt to get on it. The face 

 of an objective cannot be cleaned without doing harm to it. 



3. Keep both eyes open when looking through the micro- 

 scope. Also get into the habit of using either eye. 



4. When examining an object, keep one hand on the fine 

 adjustment, and keep screwing it up and down slightly. In 

 this way parts of the object at different depths are brought 

 into focus, and a much clearer idea of the object is obtained. 



5. With a high power, use a small diaphragm : the amount 

 of light will be somewhat diminished, but the clearness and 

 definition much increased. 



6. See that the body of the microscope slides smoothly in 

 its tube. If it does not, remove it, and clean it by rubbing 

 with a few drops of olive oil ; wipe off the oil before replacing 

 in the tube. Clean the inside of the tube in the same way. 



7. The object may appear indistinct from dirt in any of 

 the following places, i.e. on the eye-piece, the objective, or the 

 cover-glass. If it be on the cover-glass, the dimness varies 

 when the slide is moved ; if on the eye-piece, it varies when 

 this is rotated ; if not on either of these, it must be on or in 

 the objective. 



The eye-piece and the lower surface of the objective may 

 be cleaned with chamois-leather or silk. If the objective is 

 smeared with glycerin, wash it carefully, then dry with a 

 soft Jbandkerchief. Canada balsam, which sometimes gets on 

 the objective, may be removed with a drop of benzol on a 

 handkerchief. It is, however, safer to leave this to an optician 

 or to the demonstrator, as a very small quantity of benzol 



