58 ELEMENTARY CHEMICAL MICROSCOPY 



supported by the substage the plate may lie upon the work 

 table, its angle of inclination being obtained by means of a pro- 

 tractor and the plate held in place by means of plasticine for a 

 temporary mounting. A very simple arrangement of the 

 Cheshire plate may then be as indicated in the diagram, Fig. 24, 



FIG. 24. Obtaining Polarized Light by Reflection. 



the support being an ordinary object slide, while the polarizing 

 plate consists of a half -slide, ground upon its lower surface by 

 rubbing upon a piece of glass carrying very fine emery and tur- 

 pentine. After cleaning off the abrasive, the ground surface 

 is blackened. A small mass of plasticine is placed upon the 

 slide and the polarizing plate is pressed down until the proper 

 inclination is obtained as indicated in the diagram. Thus pre- 

 pared, this polarizer is pushed into the opening in the horse- 

 shoe base of the microscope until the center of the plate falls in 

 the optic axis of the microscope, the mirror of the instrument 

 having been removed or swung aside. Light thrown upon the 

 plate will be polarized and reflected in the line of the optic axis 

 of instrument. 



