44 MICROSCOPY FOR BEGINNERS. 



The beginner will not need one, but ho may desire to 

 know how to use it. Place the micrometer on the 

 stage, turn the microscope horizontal with the reflector 

 referred to above, fitted to the eye -piece. "With the 

 low-power objective focus the lines that are yfg- inch 

 apart, and draw them on the paper. Do the same with 

 every objective, drawing the y^ inch spaces with the 

 or lenses. These drawings will form the scale for 

 measuring the drawings of the magnified objects. Thus, 

 if the magnified object, when drawn, occupies two spaces 

 of your paper scale made from the y^-g- inch micrometer 

 spaces, the object will measureyl-j, or -^ inch in length ; 

 if five spaces of your scale, then it will measure yjj-^, or 

 g 1 ^ inch long ; if only one-half a space of your scale, 

 then it will measure one-half of y^- of an inch ; if one- 

 fourth of your scale space, then its actual length will be 

 j-J-5- inch. If the or -^ objective is used in making 

 your scale from the 10 * 00 inch micrometer spaces, then 

 each division on the paper will represent 10 * 00 inch, and 

 if the drawing of the object measures two of these 

 spaces on your scale, the real length of the object will 

 be y^j- inch, or T fj-. It is perceived that the stage 

 micrometer cannot be used for measuring objects direct- 

 ly, but only by applying the drawing of the magnified 

 micrometer spaces to the drawing of the magnified ob- 

 ject. 



The micrometer can also be used to ascertain the 

 power of the microscope. If each of the y^-g- inch spaces 

 measures, when drawn on the paper, T ^ inch, that com- 



