256 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
When using oblique light it is important that the diaphragm be 
placed on the side of the eye-piece nearest the mirror. For example, if 
the mirror is placed at the left of the stage, the screw F should be at 
Fig. 18. Fig. 16. 
A 
the left of the Microscope-tube. The eye-piece can be revolved to bring 
the diaphragm into the required position, and this revolving motion will 
also give a variety of beautiful effects. 
The diaphragm works equally well with all objectives which I have 
used, and will, I think, repay all workers with the Microscope for the 
practice necessary to become familiar with its use. 
Substage Condenser.* — Mr. Hyatt stated that the condenser which 
he exhibited to the New York Microscopical Society was constructed by 
himself on the principle announced some time since by Prof. Alfred M. 
Mayer — three plano-convex lenses, the largest one, of 2 in. focal 
distance, with a central stop, placed below, and two smaller lenses, 
paired, with their convex surfaces opposed to each other, and placed 
* Journ. New York Micr. Soc., vii. (1891) p. 54. 
