66 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



MICROSCOPY. 



A. Instruments, Accessories, etc.* 

 (1) Stands. 



Small Comparator.! — This instrument (fig. 2), made by the Cam- 

 bridge Scientific Instrument Co., consists of a cylindrical steel tube about 

 .")()( i mm. long which is supported in geometric bearings on a rigid 

 frame, and can be fed backwards and forwards by means of a micrometer 

 screw of 1 mm. pitch. The micrometer head is divided in 100 parts 

 and readings can be estimated to 0"001 mm. The screw has a pitch of 



Pig. 2. 



1 mm. and is free from backlash. Two Microscopes with achromatic 

 objectives are clamped to the steel tube. They are fitted with the Lucas 

 slow motion focusing mechanism which gives a very smooth movement 

 and is also free from backlash. The scale under observation is sup- 

 ported on the base of the instruments and scales of any length may be 

 checked. 



* This subdivision contains (1) Stands : (2) Eye-pieces and Objectives ; (3) 

 Illuminating and other Apparatus ; (4) Photomicrography ; (5) Microscopical 

 Optics and Manipulation ; (6) Miscellaneous. 



t Cambridge Scientific Instrument Co., Ltd. 



