148 



INSTRUMENTATION 



contrast accessories for their incident-illumination microscope. The 

 phase objectives are a series of achromatic objectives which carry in 

 the mount a beam splitter and a diffraction plate located above the 



Fig. III. 10. The phase contrast microscope available from Cooke, Troughton and 



Simms, Ltd., for vertical incident illumination. The aperture through which Hght 



is incident on the beam spHtter is more easily seen in the mount of the objectives 



beside the stand. Courtesy of Cooke, Troughton and Simms, Ltd. (1949). 



beam splitter (cf. Taylor, 1949) and which have been corrected for 

 zero cover-glass thickness. The illuminator tube carries a single di- 

 aphragm with an annular aperture. Means are provided to move the 

 condenser diaphragm in and out of action and to center it. The power 



