120 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
sliding eye-lens combined with a collective system consisting of two 
single lenses, the lower one of which may, by means of a sliding tube, 
be focused with respect to the upper focal plane of the objective. 
Fig. 14. 
Czapski’s Ocular Iris-Diaphragm with Eye-piece.* — This apparatus, 
for the accurate examination of the axial images of small crystals, con- 
sists, as seen in fig. 15, of a small iiis-diaphragm fitting in the upper 
Fig. 15. 
Fig. 16. 
end of the tube, with a sleeve attached, in which slides a Bamsden 
eye-piece. In the figure, A shows the longitudinal section, and B the 
iris-diaphragm seen from above. 
Microscope for Opaque Objects, f — M. C. Fremont describes the 
method of illumination which he uses for opaque objects under the 
Microscope. The method is somewhat similar to that adopted in the 
Zeiss vertical illuminator, but instead of the reflecting prism the author 
uses a mirror. The pencil of light L (fig. 16) reflected from the mirror 
D, passes through the opening E E into the body-tube A of the Micro- 
scope, where it meets the concave mirror C. This mirror is movable, 
* Zeiss’ Catalogue, No. 30, 1895, p. 87. 
f Comptes Rendus, exxi. (1895) pp. 321-3.. 
