13 

 By comparing Hulbert's work with that of Burt , it may be seen 



how very pure ocean water is. Burt measured extinction of light in 

 Chesapeake Bay caused by suspended particles. He concluded that particle 

 concentration ranges from 1 to 60 parts per million by volume and that 

 the average particle radius is 6x10"^ cm. Since coastal water is much 

 less absorbing than bay water, it may be concluded that it is very dust 

 free and contains much less than the 1 part per million of suspended 

 particles than was used in the example of the section, Absorption Pro- 

 cesses at Very High Frequencies. 



The best measurements of infrared absorption seem to be those of 



14 

 Plyler and Acquista whose results are graphed below. These authors 



used a Perkin-Elmer double beam spectrometer and three different sample 



thicknesses of water. 



100 

 80 

 60 

 40 

 20 





10. 



Liq H2O 



%T 



10 l4 18 22 26 30 34 38 42 |a 



The graphs plot the percentage transmission against wavelength in microns. 

 The numbers on the graphs give the sample thicknesses, a gives the ap- 

 proximate absorption coefficient at the specified wavelength in cm~l, 



15 

 Cartwright states that there is a gradual increase in T from 50 to 150 



microns. 



-12- 



