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INSTRUMENTATION 



Fig. III. 5.1. (a) Cell and diaphragm for Spencer single-unit substage condenser 

 mount, (b) Substage condenser in Spencer single-unit mount, (c) Spencer con- 

 denser for phase microscopy with diaphragm turret mount, (d) Spencer phase 

 microscope equipped with turret mount for diaphiagms and condenser. Courtesy 



of American Optical Co. (1949, 1950). 



