208 THE USE OF THE MICROSCOPE 



Half -silvered Cube. — The li;ili'-silvered cube (Swan cube) 

 is fitted for vertical illumination, as well as for use in the 

 Abbe camera. (It has been so employed by the Spencer 

 Lens Company.) It shows the pencil point clearly, in the 

 camera lucida. 



Dark Field. — Promising for further research is the use 

 of the dark field with water-immersion objectives of 1.2 

 or 1.25, on objects in watery fluids in their natural state 

 or fixed. It is perhaps possible that the modern study 

 of stained balsam preparations may be widely supple- 

 mented by the study of unstained objects, as was done in 

 the early days of the water-immersion objective. 



Source Diaphragm. — The removal of glare by the use 

 of a sufficiently small diaphragm on the source of light 

 seems to the writer one of the important points for future 

 microscopy, both in routine and research work. 



