ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
383 
or the cylinder diaphragm. The iris diaphragm which is attached to 
the same piece gives an aperture of from 1 to 32 mm. 
The central illumination is marked by the snapping of a spring. 
Oblique illumination is effected by turning the screw-head t'. The 
whole illuminating apparatus is attached to the prism P in such a way 
that it can be easily raised and lowered by means of the screw-head T, 
while the pin b serves as a guide for the exact centering 
For the introduction of blue glass, polarizer, &c., the iris diaphragm 
holder can be separated from the condenser and displaced from its 
central position to one side in the direction of the arrow t'. 
Reichert Movable Object-stage. — The latest form of this stage is 
represented in two-thirds its natural size in fig. 43. The screw-head 
and pinion by means of which the displacement of the objects in two 
Fig. 43. 
rectangular directions is effected are placed side by side. Both slides 
are provided with scales and verniers, and the circumference of the stage 
with a divided circle. 
For the reception of culture-plates the object-holder e e can be 
removed by raising the screw /. 
This stage is only used on Reichert stands No. 1 a and 1 b. 
Optical Projection.* — Sir David Salomons, in a lecture before the 
Royal Institution, gave a general survey of the subject of Optical 
Projection. The apparatus employed was a modified form of that of 
Mr. Lewis Wright, and was constructed by Messrs. Newton, of Fleet 
* Proc. Roy. Inst., xiii. (1893) pp. 534-9. 
