24 THE MICROSCOPE 



Rules for" Focusing 



1. Revolve the nosepiece until the shorter objective is in a direct 

 line with the tube. A click will be heard when this is accomplished. 



2. Place your prepared slide on the stage so that the specimen is in 

 the center of the opening of the stage. 



3. Turn the mirror toward the nearest source of light. Manipulate 

 it until a bright area appears on the slide. 



4. While looking at the microscope from one side, turn the coarse 

 screws clockwise until the low-power objective is one eighth of an inch 

 from the slide. 



5. Then look through the eyepiece and turn the coarse adjustment 

 screws toward you (counterclockwise) until the specimen is clearly 

 seen. If you wish to see more of the specimen than is shown in the 

 field of vision, take hold of the slide with your thumbs and slowly 

 move it in different directions. 



6. Turn on your high-power objective. Listen for a click. 



7. Use your fine adjustment screws. Turn them carefully (clock- 

 wise) until the object is clearly seen. The fine screws should be used 

 constantly in focusing with high power in order to see all that can be 

 seen. 



Problem. How does an object appear when seen through the micro- 

 scope f 



Material : Compound microscope, slide, cover slip, piece of printed paper 

 with very small type. 



Method : Place a drop of water on the slide. Place a small piece of 

 printed paper in the water and cover with a cover slip. The piece of paper 

 is now mounted. 



Lay the prepared slide on the stage, with the object as near as possible to the 

 center of the hole in the stage. Follow your rules for focusing under low power, 

 then under high power. 



I. Look through the microscope at the printed letter. 



II. Describe the texture of the paper as revealed. 



III. Draw the single letter, preferably the letter " i," exactly as it appears 

 under the low power. Note any apparent change in position. 



IV. By means of a ruler measure your drawing; then measure the letter 

 unmagnified. How many times does the low power appear to magnify ? 



