648 EIGHTH PACIFIC SCIENCE CONGRESS 



Formulation of Structure 



This experience indicates that the vakie (P) of a property at a 

 depth (z) in the sea may be expressed by 



P = /i log 2 + c (1) 



where k and c are constants within the limits (Zj and Zo) of a particular 

 zone. However, there is some variation in the data and other curves 

 of similar form were examined to determine if as good a fit could be 

 obtained. Curves of the forms 



P = ^ log (z^ - z,) -\- c 

 log P c= kz -\- c 



log P = ^ log 2 -j- C 



log P = k (log Z2 - log Zi) -f c 



log P - k (Z2 - Z:,) -\- C 



log P ==. A log (Z. - z,) -i^ C 



were examined. However, only Equation 1 provided a simple relation, 

 and subject to further discussion, it is accepted as the most plausible 

 expression of the facts. 



The slope of the gradient (k) may be evaluated from the data as 



^2 - ^1 



^ = ~ 17 (2) 



log ~ 



where the subscripts refer to the values at the ujjper and lower limits 

 of the zones. 



The constant (c) may be evaluated by setting z = 1 in Equation 1.. 

 whence 



c = P' (3) 



where P' is the abscissa of the gradient extrapolated to unit depth. 



Characteristics of the Log-Plot 

 It is important to realize that the log-plot is a technique for inter- 

 preting the sea water structure from serial observations. It is realistic 



