iv CONTENTS 



Page 

 y. Description of standardized apparatus and method for the study of 



color perception 4G 



1. General description of the optical system 47 



2. Description of the mounting of the apparatus 51 



a. Operation of tlie system 



3. Description of color spacing and reversing device GO 



a. Double-slit mechanism and calibration 



b. The episcotister table 



4. Description and cost of parts of apparatus 70 



a. Sources and their control 



Sunlight and heliostats 

 Arc lamp 

 Nernst lamp 

 Slits 



b. Lenses 



Condenser 

 Collimator 

 Objective 

 Small projection 



c. Prisms 



Refracting 



Total reflection ^ 



Double image 



d. Episcotisters and motor; iris diaphragm 



e. Mirrors 



f. Instruments for measuring wave-length and intensity 



Selenium cell and auxiliary apparatus 



S]3ectrophotometers 



Flicker photometer 



Spectrometers 



g. Experiment box 



VI. Conclusions and summary of recommendations 87 



