616 
SUMMARY OF CURRENT RESEARCHES. 
Messrs. It. and J. Beck’s Large “Continental” Model Microscope. 
— This instrument (fig. 55) is on the model of the Continental Microscope, 
the special feature being the improved slow motion, which, Messrs. Beck 
claim, is extremely delicate, and being made without adjusting pieces 
cannot become deranged. The instrument has a rack and pinion and 
centering substage carrying condenser with iris diaphragm. The draw- 
tube is nickel-plated and graduated in millimetres. The whole instru- 
ment is heavy, rigid, and compact. 
Koristka’s Microscopes.* — The large model I a (fig. 56) is provided 
with a movable stage having two rectangular movements besides the 
movement of rotation about the optic axis. Each of the rectangular 
movements is of the extent of 20 mm., so that a space of more than 
400 sq. mm., can be explored. A vernier for each movement allows of 
readings to 1/10 mm. The movements are sufficiently rapid, and at the 
same time of absolute precision. By means of the verniers and scales 
any given point of a preparation can be quickly found again. The stage 
is specially intended to hold the ordinary glass slide, but allows of the 
adaptation of slides of any dimensions. 
The small model IX. (fig. 57) has the base and column of nickeled 
cast iron. The stage has dimensions 75 by 70 mm., and the body-tube 
has a fixed length of 16 cm. The rack-and-pinion movement is of 
special construction, so that the smallest displacements can be made, 
and it is possible to focus for magnifications of more than 300 diameters. 
The instrument is provided with a concave mirror with lateral adjust- 
ment, and with diaphragms cut in a disc applied to the under surface of 
the stage, so that it can be rotated and the central position of each 
aperture marked by a catch. 
This stand is specially intended for small schools, as an instrument 
of instruction for boys. 
Koristka Mineralogical Microscope.-j- — The model C (fig. 58) for 
mineralogical work, has coarse-adjustment by rack and pinion, and fine- 
adjustment by micrometer-screw with head divided into 5/1000 mm. 
The rotating stage has a diameter of 100 mm. and is divided in 
degrees with a vernier reading to 10'. There are divisions on the 
stage for the orientation of the preparation. The arrangements for 
polarized light, and for passing from convergent polarized light to 
parallel polarized light, are very simple and rapid. The double mirror 
is adjustable laterally and in height. The polarizing nicol has a large 
field. The analyser has a circle divided in degrees, and allows of the 
use of any eye-piece and also of the introduction of other accessories 
between the eye-piece and the analyser. There is a slide-piece for 
the reception of Klein’s plate or other accessory. A large opening in 
the body-tube allows of the introduction of a second analysing nicol be- 
tween the objective and the eye-piece. The nicol is so adjusted as to 
produce no displacement of the image, and is united to a lens which 
maintains the constancy of the focal length of the system of objective and 
eye-piece. This nicol, which is of the Glan-Thompson construction, 
does not greatly restrict the field of view. 
F. Koristka, Catalogo Illustrato Descrittivo, N. 7, Milan, 1894. f Op. cit. 
