222 
SUMMARY OF CURRENT RESEARCHES RELATING- TO 
all of the most stable construction, so that there is perfect rigidity and 
accuracy of centering throughout. The vertical adjustment of this sec- 
tion of the substage permits the condenser to be brought in immersion 
contact with the object-slide, or to be placed in any other position desired 
without reference to the position of the upper iris diaphragm. The 
Fig. •* '. 
lower section of the substage carries the large iris which is used below 
the condenser. This diaphragm may be swung from under the conden- 
ser to the right of the instrument. It is so mounted that it may be 
rotated upon its own axis, and is laterally movable by rack-and-pinion 
when oblique illumination is desired. 
Bausch and Lomb’s Revolving Mechanical Stage.— The entire 
stage (fig. 55) rotates on its axis, the circumference being divided into 
360 degrees, and provided with vernier reading to tenths of a degree. 
The rectangular movements and object-carriers are the same in con 
struction as those of the C£ Attachable Mechanical Stage.’ The gradua- 
