ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



459 



apparatus above and below the stage. The stage is covered with 

 vulcanite and measures 4 by 4 in. The analyser and polariser are 

 simultaneously rotated by means of cogwheels connected by a shaft H, 

 so placed that it does not interfere with the use of the stage : there is 

 a distance of 2 in. from the centre of the stage and the edge of the 

 slow-motion pedestal, and the cogwheel shaft is 1*8 in. from the centre 

 of the stage. The analyser K is carried on a swinging bracket L, and 

 is usually supplied on a sliding dovetail M, so that its height can be 

 adjusted to the eye-point of the Microscope, and the slide is provided 

 with a clamp to fix the analyser in any position. 



Within the I ody-tube is a slot P, through which an inner tube 

 carrying a Bertrand lens can be slid up and down. Below the Bertrand 

 lens is an iris diaphragm S. 



Two kinds of condensers are supplied, the simpler form (fig. G6) 



Fig. G7. 



consisting of a couple of lenses placed above the polariser. The more 

 complete form (fig. 67) consists of an achromatic and aplanatic con- 

 denser 1*0 N.A., or semi-apochromatic condenser i'2 N.A., and has a 

 pivoted top lens which can be swung out of the optic axis by means of 

 a handle below the stage. An iris diaphragm is affixed to the condenser 

 to reduce the aperture when necessary. 



The top lenses of the eye-pieces have a special adjustment to enable 

 either the micrometer or the cobwebs to be focussed. The principal 

 cobweb of the crossed pair is marked by a V. 



Zeiss' Rotary Projection Slide Carrier.* — E. Richter describes 

 this apparatus, whose general nature is that of a square rotary drum 

 with its axis transversely in the axis of the optical lantern. It is 

 placed between the illuminating apparatus and the objective. When 



* Zeits"lir. wise. Mikr., xx. (1903) pp. 132-7 (2 figs.). 



