(fig. 22). This suggests that the islands are located in a region bounded 

 by intermediate water masses from a different source and supports the 

 schematic figure 202 in Sverdrup et al. (1942:717). 



Also interesting to note is the shape of the T-S curve at the 

 salinity minimum. There are a number of stations such as station 29 

 (fig. 22), where the salinity remains essentially constant between the 

 extremes of sigma-t mentioned above, which might suggest mixing of 

 the two types of water. 



To illustrate these observations, figure 23 has been prepared 

 showing schematically two types of water at the salinity minimum which 

 were separated arbitrarily at 26. 5 sigma-t. Cross-hatched zones in- 

 clude the stations of constant salinity throughout the sigma-t rajige. The 

 lack of a more definite flow pattern on this diagram is in agreement with 

 the averaged dynamic heights for the lower intermediate flow, which show 

 only a weak net circulation. 



Bathythermograph Data 



Bathythermograph data are again included as a record only in 

 vertical sections on figure 24. 



Summary of Cruise 



Cruise 20 of the Hugh M. Smith took place during oceanic winter 

 conditions with trade wind weather. 



The hydrographic data showed considerable complexity extending 

 down through the salinity minimum layer with four major vortices which 

 obscured any mean flow pattern. Average dynamic heights at 300 m. 

 relative to 1, 000 m, indicated a southwesterly drift through the main 

 survey region. Those at the surface relative to the 300-m. level re- 

 vealed a slightly stronger easterly drift. These two systems combined 

 to give a net easterly flow along the island chain and no net current in 

 the northern section of the survey region. 



The large number of vortices show that the survey region is one 

 of dissipation of energy with little or no net transport. The absence of 

 any "streams" impinging on the island chain either at surface or inter- 

 mediate depths suggests the existence of mechanisms for vortex genera- 

 tion other thaji those associated with current shears. 



17 



