Spectroscopic Eye-pieces. 
Spectroscopic Eye-piece. Eye-pieco with slit mechanism 
between the lenses. The upper achromatic lens adjustable to 
focus on the slit. Amici prism to place over the eye-piece. The 
whole connected with the body by a clamping screw .... 
^Spectroscopic Eye-piece (Micro-spectroscope) after 
Abbe, Achromatic upper lens adjustable to focus on the slit as 
above. Mechanism between the lenses for contracting and ex- 
panding the slit by symmetrical movement of the laminae (after 
Merz) by means of the screw F; these may be sufficiently widely 
separated so as to open the whole visual field. The screw H 
serves to reduce the length of the slit to such an extent, that, 
the comparison prism being inserted, the image of the object 
under investigation completely fills the slit. Comparison prism 
with lateral frame and clips to hold the object and the mirror. 
All these parts in a drum combined with the eye-piece. 
Above the eye-piece, an Amici prism of great dispersion, 
which may be turned aside about the pivot {K) 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 mount of the prism ; the divisions of the scale indicate in 
decimals of a micron the wave-lengths of the section of the 
spectrum superposed by them. The screw P is for adjusting the 
scale relative to the spectrum. 
