162 MICRO-SPECTROSCOPE AND POLARISCOPE \_CH. VI 



Fig. 138 



Pig. 139 



Fig. 140 



Fig. 138. (1). Section of the tube and stage of the microscope with the 

 spectral ocular or micro-spectroscope in position. 



Amid Prism (g 210).— 7^ direct vision prism of Amid in which the cen- 

 tral shaded prism of flint glass gives the dispersion or separation into colors, 

 while the end prisms of crown glass cause the rays to emerge approximately 

 parallel with the axis of the microscope. A single ray is represented as enter- 

 ing the prism and this is divided into three groups (Red, Yellow, Blue) , which 



