CHAPTEE V. 



ON VIEWING MICROSCOPIC OBJECTS BY 

 POLARIZED LIGHT.* 



"The addition of a polarizing apparatus to a microscope 

 will be ere long" considered as an indispensable accompa- 

 niment to that instrument, whether we consider its 

 peculiar properties or the brilliant colours it gives to all 

 bodies affected by it. The apparatus which I have 

 contrived for this purpose is extremely simple, and may 

 readily be attached to, or removed from, the microscope 

 without either disturbing it or the object under considera- 

 tion. It consists of two small tubes, containing single- 

 image calcareous prisms, or plates of tourmaline ; one of 

 which is placed under the stage of the instrument, and 

 used in the same manner as Goring' s illuminator or 

 plain diaphragms. — (See ' Microscopic Illustrations,' new 

 edition, p. 111.) 



" An intense light is to be directed through it, and the 

 instrument adjusted to the object in the usual way. The 

 object wiU present the same appearance as without the 

 polarized or lower prism. If, however, a second tube 



* Prit chard's List, page 19. 



