Figure 12. Comparison with the deviations from the linear surface (Figure 
10) shows that the area of relatively high positive deviations again 
delineates the general area of maximum mean particle size that occurs in 
the observed map of Figure 8. 
The deviations from the quadratic surface for mean size contain 
100.0 - 47.7 = 52.3 percent of the total map variability. Inasmuch as the 
deviation map still carries geologically identifiable patterns, it was 
decided to fit the cubic surface to the mean size data. The cubic surface 
map is shown in Figure 13, and the deviations from it are shown in Figure 
14. 
The cubic surface is noteworthy in that it shows a bulge of coarse 
mean sizes associated with the inlet mouth, but this bulge is somewhat 
skewed to the northeast, and in a broad way it is aligned with the path of 
the outward-flowing current shown in Figure 6. The deviations on the cubic 
surface show clearly that the alignment of the major trend of larger 
diameter grains is centered on the zone of inlet outflow. The trend of the 
zero-deviation contour in the region of inlet outflow suggests a weak 
effect of the outflow current on mean size all the way to the pier in the 
northeast corner of the map. This was suggested in a previous study of the 
same data (Harrison and Morales-Alamo, 1964) that employed conventional con- 
touring techniques. The inference from Figure 14 is that a weak effect of 
the inlet current on grain size in the vicinity of the pier may indeed 
have existed. That is, the trend surface technique constitutes a sensitive 
and objective method for examining the influence of the inlet on grain size 
both over the full inlet area and over the smaller zone of the dominant 
current. 
Patches of the deviation map of Figure 14 that are outlined by 
negative contours (-0.05) reveal weak secondary trends toward finer sizes 
roughly parallel to the "ridge" of coarse sizes. At least two hypotheses 
can be advanced for this pattern: (1) the tendency of the finest particles 
to lie on the flanks of the "ridge" is merely a reflection of the magnitude 
of the discrepancy between coarse grains (associated with outflow from the 
inlet), and the finer grains already present in the inlet prior to initia- 
tion of the outflow; or, (2) the tendency toward finer sizes on the flanks 
of the ridge reflects an actual realm of sedimentation dynamics in which 
successively finer grained particles are progressively deposited over 
areas of continuously decreasing current velocity. 
Examination of Figure 14 suggests that the latter hypothesis is 
probably the more satisfactory one. The weak trend of slightly coarse- 
grained materials associated with the breaker zone at the pier is not 
present on the north side of the "ridge" of higher values. This suggests 
deposition of finer particles on coarse ones that would ordinarily be 
present in the breaker zone. If the observed ridge pattern is due to the 
