80 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
between the rubber and the metal. This form of stage will never warp, 
as plates applied with screws will do, and retains its finish indefinitely. 
Figs. 5 and 6 show how an iris diaphragm is used in the plane of the 
stage, either with or without the condenser, so as to give any desired 
size of aperture, even sufficient for the condenser to be used through it 
in oil-immersion contact with the slide if desired. The advantage, of 
such a diaphragm is apparent, as it is thus in the only position at which 
the volume of light entering the objective can be varied without chang- 
ing the aperture of the illuminating cone. Two forms have been 
Fig. 4. 
adopted: for some stands, a shallow mounting which screws to the 
underside of the stage and forms a part of it (fig. 6) ; and for all in- 
struments provided with the complete substage, a deeper detachable 
form (fig. 7), A being the ring by which the diaphragm is operated. 
Microscope with a New Mechanical Stage. — The accompanying 
figure (fig. 8) represents a Microscope made by Messrs. Watson and 
Sons, having a new form of mechanical stage designed by Mr. E. M. 
Nelson. The mechanism of the stage has been described in this Journal, 
1888, p. 477, 1893, p. 236, and 1897, p. 185, with working drawings ; but 
as yet no woodcut of the Microscope itself has appeared. 
