The points for the salinity (0 D 2 °/oo isopleth interval) 

 were taken from the T/S curves, and those for phosphate (0 o 2 ugat/1 

 isopleth interval) and oxygen (0. 5 ml/1 isopleth interval) were read 

 from the station curves and plotted,, In each case the observed values 

 were also plotted,, Finally, the section plots for each of the three 

 fields, -salinity, phosphate, and oxygen, were in turn placed over the 

 sigma-t profile and isopleths drawn allowing them to run smoothly 

 and as nearly parallel with those of the sigma-t surfaces as possible 

 without violating the observed points (figs,, 8-10)„ Each of the fields 

 was plotted only to a depth of 500 meters, thus permitting greater 

 detail within the transition layer,, 



The principal feature of the sigma-t profile (fig„ 7), as 

 with the previously described temperature sections, is the well 

 developed gradient which lies at a minimum depth at the northern 

 boundary of the Countercurrent (10 N Q ), deepening to the south, 

 with the maximum depth at the southern boundary of the Counter - 

 current (5° N„)„ North of 10° N„ „ i„e. , in the North Equatorial 

 Current, the distribution of the sigma-t surfaces with depth results 

 in a less well defined density gradient,, At the Equator, the equato- 

 rial divergence is reflected in a slight "doming" of the sigma-t surfaces. 



The salinity maximum at about 150 meters, 2° to 5 S. 

 (fig„ 8), corresponds with that shown by Cromwell (1951, figs e 12 

 and 13), Cromwell (1954, figs c 8, 18, and 30) and by Mao and Yoshida 

 (1953, figc 15)„ In Cromwell's 1954 report, a tongue of high salinity 

 (34.8 °/oo) is continuous from the northern to the southern limits of 

 the sections; in the 1951 report, the bridge is continuous on the sec- 

 tion along 172° W„ longitude but interrupted between about 15° N. and 

 9° N,, on along the 158th meridian,, Similarly, although the situation 

 is less well defined, in figure 8 of the present report the tongue of 

 high salinity is interrupted between 13° N„ and 8 N The deep tongue 

 of low salinity water (34„ 2 °/oo) centered at about 300 m„ , 19 N„ , 

 is rather characteristic of this area in equatorial Pacific. The same 

 may be said for the low salinity waters at the surface between 5° N„ 

 and 12° N„ , the zone of the Equatorial Countercurrent and the high 

 rainfall belt c 



The values for surface phosphates along the section 

 (figc 9) are somewhat irregular, but there is evident enrichment of 

 the surface layers immediately south of the Equator (0 o 6 to o 8 ugat/1), 

 with a decrease to 0„ 2 |xg at/1 in the northern half» At about 8 - 9 N„ , 

 the boundary zone between the North Equatorial Current and the Equa- 

 torial Countercurrent, the cooler, nutrient-enriched waters are to be 

 found slightly above 100 meters, but do not reach the surface 



