OOll 



500 

 Uc3i^e- length m. jx 



Fig. 4. — Showing the average values of vertical extinction coefficients of sea-water 



Fig. 4, which gives the average vertical extinction coefficients of sea- 

 water for all classes of For ell's scale. In this figure the results of 

 Professors C. L. Utterback and W. Jorgensen for deep sea-waters and the 

 absorption coefficient for distilled water by W. R. Sawyer are also 

 reproduced (line (2) and (1) respectively). 



Looking through the figure we noticed that the most transparent 

 wave-length moves towards the side of long wave as the colour of sea 

 becomes yellowish. The change of wave-length is, however, more 

 remarkable for bluish transparent sea-water. The minimum vertical 

 extinction coefficients and the wave-lengths for them are shown in table 2. 



Table 2 — Minimum Vertical Extinction Coefficients 



The Colour 

 of Sea. 



Minimum of 



Vertical 

 Extinction 

 Coefficient. 



Wave-length for 



Minimum Vertical 



Extinction 



Coefficient. 



Transparency. 



Mean of Stations 

 of Observation. 



Average of 

 Near Japan. 



302 



