84 
brought to it by a reflecting prism arranged above it and a 
lateral tube d with collimator lens, diaphragm carrier n and 
mirror S (or incandescent lamp). 
In the upper opening of the box A either an eye-piece may 
be inserted and, by means of a sliding sleeve, made to accurately 
focus on the slit, or, instead of this (after proper adjustment of 
the image of the specimen to focus on the objective slit), the 
spectroscopic apparatus a'A'BC may be adapted and fixed in 
the proper azimuth by a click mechanism. This apparatus consists 
of the casing A' which on one side, the upper end of a', contains 
a collimator lens I, which serves to parallel the cone of rays 
proceeding from the objective before they enter a Rutherford 
prism P of great dispersion. By the lens I' on the other 
side, at the lower end of B, the parallel rays proceeding from 
the prism are again brought to a focus ; and this real spectrum 
is observed through an eye-piece L. By 2 slit mechanisms mounted 
at right angles to one another and actuated by the screws t t', 
u u' in the focal plane of the eye-piece, the visual field can be 
limited at pleasure after Vierordt's manner. 
By means of two lenses shown at (7, an image of a wave- 
length scale is projected on the spectrum by reflexion from the 
end-surface of the Amici prism, which is illuminated by the 
mirror S' and put out of action by closing the shutter d'. Ad- 
justment of this scale is made by inclining the whole scale-tube C 
by means of the screw w with its counter spring v (Figs. 41 
and 42) (vide Zeitschr. f. wiss. Mikroskopie V, p. 289, 1889) . 
