156 MICRO-SPECTROSCOPE AND POLARISCOPE [ CH. VI 



FIG. 134 Abbe's Micro-spectroscope. FIG. 135. 



Longitudinal Section of Slit Mechanism separately, 



the whole instrument. (Plan view, Full size. ) 



(Y 2 Full size.) 



" The eye lens is adjustable so as to accurately focus on the slit situated be- 

 tween the lenses. The mechanism for contracting and expanding the slit is 

 actuated by the screw F and causes the laminae to move symmetrically (Merz's 

 movement) . The slit may be made sufficiently wide so as to include the whole 

 . visual field. The screw H serves to limit the length of the slit so as to com- 

 pletely fill the latter with the image of the object under investigation when the 

 comparison prism is inserted. The comparison prism is provided with a 

 lateral frame and clips to hold the object and the illuminating mirror. All 

 these parts are encased in a drum on the ocular," 



"Above the eye-piece is placed an Amid prism of great dispersion which 

 may be turned aside about the pivot A', so as to allow of the adjustment of the 

 object. The prism is retained in its axial position by the spring catch L. A 

 scale is projected on the spectrum by means of a scale tube and mirror attached 

 to the prism casing. The divisions of the scale indicate in decimals of a micron 

 the wave length of the respective section of the spectrum. The screw P serves 

 to adjust the scale relative to the spectrum." 



" The instrument is inserted in the lube in place of the ordinary eye-piece 

 and is clamped to the former by means of the screw M in such a position that 

 the mirrors A and O, ivhich respectively serve to illuminate the comparison 

 prism and the scale of wave lengths are simultaneously illuminated. 1 ' 1 (From 

 Zeiss' Catalog.) 



