Figure 2. 1953 concept of equatorial circulation . By 

 the broad arrows shown on the surface we indicate the long known 

 South Equatorial Current on the left, the North Equatorial Current 

 on the right, and the Equatorial Countercurrent between them. 

 The small arrows indicating the transverse movement are based 

 on isenstropic concepts applied during this past year (Townsend 

 Cromwell, in press). The easterly flowing sub-surface current 

 underlying the Equator was discovered by use of a drift drag 

 technique during SMITH cruise l6 {Townsend Cromwell, R. B, 

 Montgomery, and E, D, Stroup, in press). By this technique 

 there was also confirmed the northerly transverse movement 

 near the surface between the Equator and countercurrent and the 

 complete lack of transverse movement in the countercurrent 

 itself. 



Figure 3. Surface temperature and phosphate. The 

 data for this diagram were drawn from SMITH cruise 8 and con- 

 sist of thermograph records of surface temperature and inorganic 

 phosphate determinations of water samples from 10-meter levels. 

 The data are lacking for the middle lower portion of this figure 

 and the course of the isopleths as drawn may differ somewhat 

 from the exact conditions existing at the time of survey. Owing 

 to suspected deterioration of one of the reagents used in the 

 chemical analysis there is some doubt as to the absolute values 

 of phosphate concentrations. We believe the error, if it exists, 

 is consistent throughout the determinations giving consistent 

 relative values and hence a reliable pattern of isopleths. 



Figure 4. Zooplankton abundance by latitude . As an 

 indicator of relative productivity we have used the volume of zoo- 

 plankton taken in hauls of a standard type described by King and 

 Demond (1953), which sample the larger niembers of the zooplank- 

 ton community in the upper 200-meter stratum of water. Daytime 

 hauls caught less, on the average, than nighttime hauls. The 

 volumes were adjusted for this variability by a method to be des- 

 cribed by King and Hida (ms. in preparation). Thus the volumes 

 represent the standing crop rather than the production, but owing 

 to uniformity of the zooplankton composition and of the temipera- 

 ture in the waters with which we are concerned, the rate of turn- 

 over probably is fairly uniform and the standing crop proportional 

 to the production. The summary of zooplankton abundance in the 

 upper panel includes all of the hauls of HUGH M. SMITH cruises 



37 



