DEPTH (m) 



050 100 150 200 250 300 350 400 450 500 550 ii>^ 



2: 



UJ 



50 100 150 200 250 300 350 400 450 500 550 Ji'^. 



Fig. 17. A sequence of sunset observations showing scattering as a function of depth and 

 frequency. Contours of equal sovmd level are two decibels apart, with lightest areas 

 denoting highest levels. Time of day of each observation is indicated in large numerals 

 above the upper right-hand corner of each record. The observations were made in 

 area A of Fig. 14; the low-frequency part of the 1906 record appears, with an ex- 

 panded frequency scale, in Fig. 16. 



18— s. I 



