To make the relations between the different fields more readily apparent, selected 

 isopleths of sigma-t have been plotted as dashed lines directly on the vertical sections of 

 salinity and phosphate and on the section of computed currents. The two shallower isopleths 

 roughly define the upper and lower boundaries of the strong density gradient in the thermocline. 



Comparison of the temperature sections from Smith cruise 14 and Manning cruise 1 1 

 indicates that changes in the minor features of the various distributions may be quite rapid; this 

 has been verified by the results of a subsequent cruise (Smith cruise 15, Austin MS. ). For this 

 reason no attempt has been made to plot any form of horizontal distribution over the area 

 covered by Smith cruise 14. 



It should be noted that the winds, atypically, were predominantly north of east over 

 the entire area during the period of the cruise (wind data are listed for each station in the 

 tabulated data). 



Computed currents--As indicated above, only the stations along 155 W. longitude 

 were of sufficient depth to permit computation of geostrophic currents relative to a 1, 000-meter 

 level of no motion (except for three stations on 180° longitude, see below). The smoothed 

 dynamic topographies of selected isobaric surfaces with respect to the 1 , 000-decibar surface 

 are shown in figure 3; the computed dynamic heights at each station are carried as dots. Owing 

 to equipment malfunctions the observations at 0°54'N. latitude and 3°00'S. latitude were too 

 shallow to permit computation relative to this surface. From these smoothed topographies the 

 currents shown in figure 4 were computed. The computation of currents becomes highly un- 

 certain, and is not attempted, within 3 of the Equator. 



In the surface layer, the Equatorial Countercurrent is found from the northernmost 

 station at 8° N. latitude to the southern boundary at 4° N. latitude; the Smith temperature section 

 on this longitude (see below) indicates the northern boundary at approximately 9 30'N. latitude. 

 The westerly South Equatorial Current is found south of 4° N. latitude. 



The three southernmost stations of the 180 longitude line reached 1,000 meters, 

 and computation of dynamic heights of isobaric surfaces relative to this level have been carried 

 out; these are carried in the tabulated data but not in a figure, and no currents have been 

 computed. Examination of the data indicates that the currents in the surface layer were variable 

 and perhaps partly easterly. 



Temperature— Temperature sections from the BT data appear in figures 5, 8, 12, 

 and 16. As mentioned above, in order to reveal detail these sections were constructed with 

 greater vertical exaggeration than those of the other variables. The BT casts from which the 

 Smith sections were drawn were taken every 10 miles between stations, and every 30 miles 

 along 155° W. longitude north of 8 N. latitude. Two casts were taken at each station; the one 

 nearest in time to the hydrographic cast was plotted in each case. The Manning sections are 

 drawn from casts made on the fishing stations only. The Manning fished one station per day; 

 the date of the first station on each line is given in the figure caption. 



On each section the downward slope of the thermocline away from the Equator to 

 north and south (as distinguished from the pronounced arching of the shallower isotherms at 

 the Equator) is evidence of the distribution of mass associated with the South Equatorial Current, 

 and the northward rise starting a few degrees north of the Equator is associated with the easterly 

 flow of the Equatorial Countercurrent. Only the Smith section along 155 W. longitude extends 

 beyond this into the North Equatorial Current, indicated by a second northward deepening. The 

 southward rise of the isotherms at the southern end of the 180 longitude line is reflected in the 

 weakening of the westerly flow indicated here by the computed dynamic heights of isobaric 

 surfaces. These gross "topographic" features, associated primarily with zonal currents, are 

 reflected in the distributions of each of the variables. In the surface layer, lower temperatures 

 at the Equator are evidence of the addition of water from somewhat greater depths. 



