ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
237 
Klein’s large universal apparatus (fig. 34) serves not only to deter- 
mine the extinctions of the different faces of a zone and to ascertain the 
directions of the optic axes, but also to measure the axial angle. The 
Microscope is placed in the horizontal position. At right angles to 
the base-plate G rises the holder T, with the divided circle K, which is 
fixed by the screw S. The rod P can be displaced in the direction of 
the axis and fixed by the screw Y. The lower end of the rod P carries 
the two arcs L and b l for the adjustment of the crystal. 
Fedorow’s universal stage for observation in parallel polarised light 
(Type I.), as made by Fuess, is represented with the neighbouring parts 
of the Microscope in fig. 35. 
The base-plate of the apparatus carries an upright with the axis of the 
divided circle T. On the inner surface of this the plate A is fastened ; 
at right angles to this rests the support for the movable axis of the 
divided circle T, at right angles to the first. On the side of this turned 
Fig. 37 . Fig. 38 . 
towards the Microscope is the sliding-piece, adjustable by the screw s, 
which carries the object-stage 0. 
For investigations in strongly refracting liquids the apparatus has 
the arrangement shown in fig. 36. In place of the object-stage O the 
holder W is attached by the screw a. The vessel containing the liquid 
is carried by the support S. When filled it can be brought into position 
from below and clamped by the screw m. 
Fedorow’s universal stage (Type II.) is shown in fig. 37. From a 
base-plate which can be firmly clamped to the stage rises the upright 
carrying the vertical divided circle. On the inner surface of this is 
• attached the sliding-piece (as in Type I.) which supports the holder of 
the horizontal circle. 
Of special eye-pieces, the one shown in fig. 38 is provided with a 
Calderon calcite plate or the Bertrand quartz plate, and is used for the 
determination of the directions of extinction in weakly doubly refracting 
substances. In order to enable the observer to look exactly at right 
angles to the stauroscopie plate, a diaphragm d is placed over the 
