The three groups of five figures corresponding to the 

 different frequency modes are arranged in the same order. 

 The first graph in each group is a scatter diagram of attenu- 

 ation versus relative oxygen content (as per cent saturation). 

 The remaining four graphs in each group show the attenua- 

 tion versus particle count for the following particle types: 

 Gonyaulax, Peridinium, broken cells (with chlorophyll) and 

 all particles collectively. As noted earlier, the attenuation 

 is given in terms of excess relative to that of the cavity 

 for the first group only (mode 1-1-1). The total attenuation 

 is given in the second two groups in view of the somewhat 

 uncertain behavior of the cavity attenuation for the modes 

 2-1-1 and 1-2-1. 



The most striking thing one observes in these results 

 is the large scatter of value of attenuation, a feature which 

 seems to be inherent in respect to a complex fluid mixture 

 like sea water - whose properties cannot be uniquely de- 

 fined in terms of temperature, salinity, and pressure alone. 

 The graphs indicate that even oxygen content and particle 

 count are insufficient as additional degrees of freedom for 

 establishing a reproducible relation for attenuation. It is 

 evident that one is confronted with the problem of a random 

 variable in dealing with attenuation in sea water. However, 

 it is tempting to anticipate that the statistical behavior of 

 the attenuation bears some definite relation to the statistics 

 of the particulate matter, oxygen content, etc. There is 

 some evidence for this in the graphs shown here, particu- 

 larly those indicating attenuation versus per cent saturation 

 with oxygen. However, in view of the rather limited sample 

 of data, there has been no attempt to carry through a de- 

 tailed statistical analysis. 



Some of the scatter in the present measurements may 

 be related to the method of sampling, effects of stirring, 

 and other factors characterizing the experimental procedure. 

 These possibilities are discussed below. 



76 



