SOME CHARACTERISTICS OP SEA WATER STRUCTURE 



645 



structure is between these limits and cannot be better defined from the 

 data. Structure D illustrates another indeterminate boundary that may 

 be interpreted as having two or one point. In structure E it is evident 

 that there is a boundary because of the discontinuity between the upper 

 and lower zones. However, since data in the zone are lacking, it may 

 be interpreted by any gradient between the limits of the dashed lines. 



The conventional interpretations are indicated by the solid boun- 

 dary zones in the figure, and the data are divided into two groups. The 

 first includes all zones such as A and C where the gradient is defined 

 by three or more points, and the probable error can be determined from 

 their scatter. The suitability of the concept of logarithmic gradients is 

 based on such data. Secondly, all zones defined by two points or less 

 are grouped together because the plot cannot be analyzed statistically, 

 and there is usually some doubt about the interpretation. These two- 

 point zones provide no proof of the validity of the concept. They may 

 be regarded as supporting evidence because they afford no contradic- 

 tions. 



Probable Error of the Log-Plot 



TABLE I 



Summary of the Experience of Fitting the Log-Plot to Serial 

 oceanographic data 



A summary of the general experience is shown in Table I. Blocks 

 of winter and summer data were taken from serial observations in the 

 ocean, well offshore, and from Georgia Strait, which is an enclosed sea 

 dominated by a large river. This analysis includes only a small part 

 of the data that have been studied by this log-plot method. 



