362 



OSCAR W. RICHARDS 



ing material may consist of calcite prisms or a special grade of Polar- 

 oid. Objectives must be obtained that are free from strain. A rotat- 

 ing mechanical stage is desirable. 



EYEPlEa 



SPIRAL FCXUSING RING 

 FOR AMICI BERTRAND LENS 



COARSE FOCUSING ADJUSTMENT 



BODY ^E 



FOCUSING EYE LENS 



ENGRAVED 

 CROSS HAIR DISC 



fYEPIECE FIELD LENS 



AMICI BERTRAND LENS 



COMPENSATING LENS 



PROTErriNG PLATE 



AHRENS 

 ANALYZING PRISM 



Fig. 8. Polarizing microscope showing parts 

 and the path of light through the instrument. 



The above minimum equipment may be added quite readily to 

 an ordinary compound microscope for polarization study. For criti- 

 cal and analytical work a standard polarizing microscope (Fig. 8) is 

 preferable. In addition to a Bertrand lens the latter has provision 

 for the insertion of retardation plates, also a rotating stage with cali- 

 brated scales. 



