312 



PRITCIIARD'S WEDGE PHOTOMETER. 



It is 



f 



admitted that if 



gh 



any 



unit 



am 



absorbent solid there pass 



a homogeneous ray 



of which n pai 



of a homogeneous 

 a are transmitted 



through the second equal stratum n 2 parts will be transmitted, and through 



such 



1.0 in 



2.0 in. 



3.0 in. 



4.0 in. 



5.0 in. 



6.0 in 



Fig. 5. 



follow with any ray if there be not 



strata n n parts, and that the same result will 

 selective absorption. 



As the result of these measures, we have then, we repeat, both in the tables for 

 each day and in the final values, numbers in a and b which should — if the wedge be 



