PARTS OF A COMPOUND MICROSCOPE. Ill 



tached to a fine screw. When it is turned in the di- 

 rection of the hands of a clock the body is lowered 

 very slowly. By turning in the opposite direction 

 the magnifying parts are raised. 



M. Stage. This is the part on which the slide 

 with the object is placed for examination. It is at- 

 tached to the arm. 



N. Clips. Two springs which are attached to the 

 upper surface of the stage and which serve to hold 

 the slide in place. 



O. Mirror. The mirror is used for reflecting the 

 light upon the object. The flat surface is called the 

 plane mirror. The hollow surface is the concave 

 mirror. The latter not only reflects but also con- 

 centrates light upon the object. 



P. Mirror Bar. This bar carries the mirror. It 

 can be turned so as to throw light upon the object 

 from any direction. 



Q. Substage. An arrangement below the stage 

 to receive various extra devices for increasing or 

 regulating the amount of light. 



S. Iris Diaphragm. This device enables one to 

 shut off or increase the amount of light that falls 

 upon the object. When the small lever beneath the 

 stage is moved toward the right the hole through the 

 stage is diminished in size. 



