THE USE OF THE MICROSCOPE. 5 



(2) With high powers the objective has to be brought so 

 close to the object that a more dehcate method of adjustment 

 is necessary. This ^flne adjust7nent is effected by a screw with a 

 milled head placed at the top of the vertical pillar forming the 

 stand. By turning the head from right to left, in the direction 

 of the hands of a watch, the body of the microscope is lowered 

 and the objective brought nearer to the object : by turning in 

 the reverse direction the objective is raised. 



In using the microscope attend to the following rules : — 



1. Always examine an object first with the low power. Having 

 adjusted the eyepiece and objective, direct the hght up the tube 

 of the microscope by means of the mirror, and then place the 

 object on the stage. Twist down the body until the objective 

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

 the microscope, and gradually twist the body up until the 

 object becomes visible. Focus accurately by means of the fine 

 adjustment screw. 



2. When using a high power begin with the objective close to 

 the cover-glass, and then focus with the fine adjustment. It 

 will facilitate the process if, while focussing with the right hand, 

 you move the object about slightly with the left hand. 



3. Take extreme care never to let the objective touch the 

 cover-glass; and never to touch or allow any dirt to get on the 

 face of the objective. The face of an objective cannot be cleaned 

 without doing harm to it. 



4. Should by any chance a drop of glycerine get on the face 

 of the objective, wash it carefully with water from a wash- 

 bottle, and wipe it gently with a silk handkerchief or piece of 

 chamois leather. Should Canada balsam be allowed to get on 

 the objective, do not attempt to clean it yourself, but hand it at 

 once to the assistant. 



5. 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 the body 

 in the tube. 



6. Keep both eyes open when looking through the microscope : 

 a very little practice will enable you to do this, and it will save 

 you much fatigue. Also get into the habit of using either eye. 



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

 of light will be somewhat diminished, but the clearness and 

 definition of the object much increased. 



