312 



peitchard's wedge photometer. 



It is of course admitted thcat if through any unit stratum of a homogeneous 

 absorbent solid there pass a homogeneous ray of which n parts are transmitted, 

 through the second equal stratum «^ parts will be transmitted, and through n such 



% 



95 



90 

 85 



80 

 75 

 70 

 65 

 60 

 55 

 50 

 45 



40 



35 



30 



25 

 20 



IS 



10 



5 



in. 1.0 in. 2.0 in. 3.0 in. 4.0 in. 5.0 in. 6.0 in. 



Fig. 5. 



strata ?i" parts, and that the same result will follow with any ray if there be not 

 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 



