CH. VI.1 MICRO SPECTROSCOPE AND POLAR/SCOPE. 



121 



Abbe's Mia o spectroscope. Fig. ir4. 



Slit Mechanism separately. 

 [Plan view, Full size.) 



Fig. 113. 

 Longitudinal Section of 

 the whole instrument. 

 (X 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 moz-e 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 ob- 

 ject and the illuminating mirror. All these parts together with the eyepiece are 

 encased in a drum. 



Above the eye-piece is placed an Amici prism of great dispersion which may be 

 turned aside about the pivot R~, so as to allow of the adjustment of the object being 

 controlled, the prism being 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. 'J he 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 prisms and the 

 scale of wave lengths, are simultaneously illuminated." (Zeiss Catalog, No. 30.) 



will 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 inverted. 

 The same is true in looking into the micro spectroscope. The actual position of 

 the different colors may be determined by placing some ground glass or some of 

 the lens-paper near the prism and observing with the eye at the distance of distinct 

 vision.* 



*The author wishes to acknowledge the aid rendered by Professor E. I*. Nichols 

 in giving the explanation offered in this section. 



