2CO 



SCIOPTICON MANUAL. 



sections of quartz, cut in different relation to the axis 

 of the crystal, producing most splendid tints; unan- 

 nealed glass, quill, Iceland spar, and, indeed, almost 

 any matter the particles of which are in a state of 

 tension. Specimens may be seen, and lists of the various 

 designs are obtainable, from opticians supplying the 

 apparatus. 



In Fig. 57, the polarizer consists of a bundle of glass 

 plates, (7, with the Nicol's prism, P, to analyze the 

 polarized, reflected rays. 



Fig. 58. 



The polariscope here represented (Fig. 58) consists of 

 a Foucault prism, of 36 millimetres in diameter, as 

 polarizer, and a Nicol's prism, of 20 millimetres in 

 diameter, as analyzer. 



