65 MICRO-SPECTROSCOPE AND POLAR/SCOPE: 



will traverse the analyzer, hence such crystals will appear as if self 

 luminous in a dark field. The experiment with these crystals from the 

 frog succeeds well with a 2 mm. homogeneous immersion. 



As further illustrations of anisotropic objects, mount some cotton 

 fibers in. balsam (Ch. V), also some of the Japanese paper (§ 72). 

 These furnish excellent examples of vegetable fibers. 



Striated muscular fibers are also very well adapted for polarizing ob- 

 jects. 



As examples of biaxial crystals, crystallize some borax, or carbonate 

 of lead on a slide as directed for the common salt, and use the crystals 

 as object. As all these objects restore the light with crossed Nicols, 

 they are sometimes called depolarizing. 



(C) Pleochromism. — This is the exhibition of different tints as the 

 analyzer is rotated. An excellent subject for this will be found in 

 blood crystals (See Part II.). 



(D) For the aid given by the polariscope in micro -chemistry, see 

 Ch. V. 



(E) See works on petrology and mineralogy for the application of 

 the micro-polarizer in those subjects. 



(F) For the production of gorgeous colors a plate of selenite giving 

 blue and yellow colors is placed between the polarizer and the object. 

 If properly mounted, the selenite is very conveniently placed on the 

 diaphragm carrier of the Abbe illuminator, just above the polarizer. 



It is very instructive and interesting to examine organic and inor- 

 ganic substances with a micro-polarizer. If the objects enumerated in 

 § 96 were all examined with polarized light an additional means of de- 

 tecting them would be found. 



REFERENCES TO THE POLARISCOPE AND TO THE USE OF POLARIZED 



LIGHT. 



Anthony & Brackett ; Behrens, 133 ; Behrens, Kossel und Schiefferdecker ; Car- 

 noy, 61 ; Carpenter, 131, 839 ; Daniell, 494 ; v. Ebener ; Gaingee ; Halliburton, 36, 

 272 ; Hogg, 133, 729 ; Lehmann ; M'Kendrick ; Nageli und Schwendener, 299 ; 

 Quekett ; Suffolk, 125 ; Valentin. 



