508 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
action more sensitive without introducing unsteadiness. The result 
attained was undoubtedly an improvement on the whole system, though 
the cost would probably limit the application to the few instruments 
required for very special and difficult investigations in microscopy. For 
high-class photomicrographic work, or where preparations had to be 
retained under observation for long periods of time, the new mechanism 
should be particularly useful, for the greater solidity of the general 
construction clearly pointed to greater precision of action and increased 
stability. 
Messrs. Bausch & Bomb’s Condenser Mounting.* — We give a figure 
of a condenser mounting with iris diaphragm recently designed by 
Messrs. Bausch and Lomb. This mounting provides a movement for the 
Fig. 55- 
diaphragm by rack and pinion. It has in addition a recess for receiving 
central stops and blue glass. 
It can be attached to an adjustable substage or to a substage fixed to 
the stage, and may be used with the high and low angled Abbe 
condenser. 
New Stage Micrometers. — At the May meeting of the Society, 
Mr. E. M. Nelson called attention to a new stage micrometer, produced 
by Messrs. Powell and Lealand, and so excellently ruled as to be worthy of 
remark: — “It comprises lOOths and lOOOths of an inch, and lOths and 
lOOths of a mm., there being 10 divisions of each set ; the finer 
divisions of *001 in. and -01 mm. being placed in the centre, the *01 
in. being on the one side, and the • 1 mm. on the other, respectively, a 
guiding line being ruled at right angles to them. The lines are fine, 
1/30,000 in., and are blackened in, and mounted in balsam. The lines 
are straight, and evenly ruled. With regard to the spacing, I have made 
exhaustive comparisons with fine micrometers by Rogers and Zeiss, and 
some others not quite so perfect. Upwards of 240 screw micrometer 
* Amer. Mon. Micr. Journ., xi. (1890) pp. 25-6. 
