CHAPTER VI 



MICRO-SPECTROSCOPE AND POLARISCOPE, 



MICRO-CHEMISTRY, MICRO-MATALXOGRAPHY 



TEXTILE FIBERS 



APPARATUS AND MATERIAL REQUIRED FOR THIS CHAPTER 



Compound microscope ; Micro-spectroscope (2 iSS) ; Watch-glasses and small 

 vials, slides and covers ( ',. 207) ; Various substances for examination (as blood and 

 ammonium sulphide, permanganate of potash, chloropbj-11, some colored fruit, 

 etc., [\ 20S-217); Alicro-polarizer (% 21S); Selenite plate (<S 227); Various doubly 

 refracting objects, as crystals, textile fibers, starch, section of bone ; Various 

 chemicals, metals, etc. 



MICRO-SPECTROSCOPE 



'i 1S8. A Micro-Spectroscope, Spectroscopic or Spectral Ocular, is a direct 

 vision spectroscope in connection with a microscope ocular. The one devised by 

 Abbe and made by Zeiss consists of a direct vision spectroscope prism of the Amici 

 pattern, and of considerable dispersion, placed over the ocular of the microscope. 

 This direct vision or Amici prism consists of a single triangular prism of heavy 

 flint glass in the middle and one of crown glass on each side, the edge of the 

 crown glass prisms pointing toward the base of the flint glass prism, i. c, the edge 

 of the crown and flint glass prisms point in opposite directions. The flint glass 

 prism serves to give the dispersion or separation into colors, while the crown glass 

 prisms serve to make the emergent rays approximately parallel with the incident 

 rays, so that one looks directly into the prism along the axis of the microscope. 



The Amici prism is in a special tube which is hinged to the ocular and held in 

 position by a spring. It may be swung free of the ocular. In connection with' 

 the ocular is the slit mechanism and a prism for reflecting horizontal rays verti- 

 cally for the purpose of obtaining a comparison spectrum {'i 201). Finally near 

 the top is a lateral tube with mirror for the purpose of projecting an Angstrom 

 scale of wave lengths upon the spectrum (i- 202, Figs. 1 19-120. ) 



\ 1S9. Apparent Reversal of the Position of the Colors in a Direct Vision 

 Spectroscope. — In accordance with the statements in \ iSS the dispersion or sepa- 

 ration into colors is given by the flint glass prism or prisms and in accordance 

 with the general law that the waves of shortest length, blue, etc., will be bent 

 most, the colors have the position indicated in the top of Fig. 123, also above 

 Fig. 119. But if one looks into the direct vision spectroscope or holds the eye 

 close to the single prism (Fig. 124), the colors will appear reversed as if the red 

 were more bent. The explanation of this is shown in Fig. [24, where it can be 



