Ol 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



tube from 35-50 mm. long, and having an outside measurement of 

 about 15 mm. (fig. (J:!) which is inserted for a distance of about 5 mm. 

 into a piece of rubber tubing 20-25 mm. long, and just wide enough to 

 grip the objective firmly. The parts are fitted together as follows : — 

 Screw the objective on to the Microscope barrel, push up the tube, 

 reverse the barrel, fill the tube slowly with water, put a cover-glass or 

 piece of paper on the top, and then insert the barrel in the stand. As 

 soon as the free end of the tube is immersed in the vessel, the cover- 

 glass or paper falls off. By shifting the rubber tubing on the 

 objective, the operator can adapt the apparatus to the height of the 

 water in the vessel and the objects therein. A depth of 10 mm. is 



Fig. 63. 



Fig. 64. 



sufficient, but if the objects are thick, or at a distance from the bottom,, 

 more water is necessary. 



If the operator prefers to work with a closed tube, the rubber tubing 

 must have a small perforation (fig. 64) to allow water to escape when 

 the objective is pushed down. 



The cover-glass forming the bottom of the tube may be stuck on 

 with marine glue or with Mendelejeff's cement. An advantage of this 

 method is that the objective may be surrounded with distilled water. 

 The cover-glass does not in any way interfere with the sharpness of the 



image. 



Simple form of Index Ocular.* — CI. C. van Walsem, after descanting 

 on the usefulness of the index ocular for demonstration purposes, point- 

 out that a simple and effective index eye-piece can be made by merely 



Zeitschr. wiss. Mikrosk. xxi. (1904) pp. 174-7 (1 fig.). 



