12 LABORATORY METHODS OF 



amined. The aperture is the circular opening in the 

 stage; its diameter can be varied according to the 

 amount of light required to see the object distinctly by 

 the use of the diaphragm, which is the circular disk 

 placed under and attached to the platform. The body is 

 the cylindrical attachment attached to the arm in front 

 and supporting the coarse adjustment, draw tube and 

 objectives. The eyepiece and the objectives are the 

 main parts of the instrument. Since the eyepiece and 

 objectives are the essential parts of the instru- 

 ment, it is very important that we know enough 

 about them to use them intelligently. The eye- 

 piece consists of a field glass and an eyeglass, 

 which are placed in the positions indicated by 

 their names. The coarse adjustment is placed on 

 the rear of the arm, at the point where the arm and 

 body meet. Its use is to obtain a focus. The fine ad- 

 justment is placed on the top of the arm and is used to 

 complete the focus obtained by the use of the coarse 

 adjustment. The draw tube is placed in the body of 

 the instrument and is used to increase its magnifying: 

 power. 



Exercise No. i. Study of the Microscope. 



Make a study of the microscope at your locker and 

 learn to use all the parts. Take the material given you 

 and find a focus of the same. Your focus is the point 



