CH. VI] MICRO-SPECTROSCOPE AND POLARISCOPE 



135 



readily seen that if the eye is placed at E, close to the prism, the different colored 

 rays appear in the direction from which they reach the eye and consequently 

 are crossed in being projected into the field of vision and the real position is in- 

 verted. The same is true in looking into the micro-spectroscope. The actual 



Abbe's Micro-spectroscope. 



FIG. 120. 



Slit Mechanism separately. 

 (Plan view, Full size.} 



FIG. 119. 



Longitudinal Section of 

 the whole instrument. 

 ( y z Full size. ) 



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

 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 completely 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 K, 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 tube 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, which respectively serve to illuminate the comparison prism and the 

 scale of wave lengths are simultaneously illuminated.' 1 ' 1 (Cut loaned by Wm. 

 Krafft, N. Y. ) 



