12 



Oliver H. Gish 



point on gradually increases to a value of about .6. Its transmis- 

 sion region extends from 442 to 358 /a/x with a maximum at about 

 415 /x/x. The degree of transmission was between that of doppel- 

 griin and glass. Here the minimum phase change falls near the 

 upper end of the transmission region. 



TABLE 2 

 Doppel-Griin 



Cyanin. — The transmission for cj^anin extended from 450 to 

 370 ix-ix, with a maximum at about 430 /xju, where it appeared to be 

 as transparent as the glass. The minimum phase change (Tables, 

 Fig. 4) is not so near the maximum of transmission as in the case 

 of the other substances tested. Considerable difficulty in obtaining 

 a coating of cyanin was had and the film here used was more 

 granular in appearance than was the case with the other substances. 



Eosin. — The film of eosin used showed but little transmission 

 for the portion of the spectrum recorded photographically except 

 very slightly in the red above 530 /a/a. 



Aniline-Orange. — Absorption for this substance becomes evi- 

 dent at about 430 /xyu, when it increases rather abruptly, being 



178 



