SUMMARY 237 



increase towards the south as it would if its origin lay at the surface westwards of the 

 region surveyed (p. 161, Table V). Convergence of this warm wedge with the coast at 

 two points (Callao and Arica) becomes significant when correlated with circumstantial 

 evidence. 



Evidence of anticyclotiic swirls 



(i) Northerly coastal drift was of most account at two localities, off San Juan and off 

 northern Peru; i.e. where the wedge was farthest from the shore (Table I). (2) Surface 

 temperatures depressed over a wide area round these points showed them to be up- 

 welling centres (Fig. 16). (3) Here also southerly drift was noted offshore (Table I and 

 Fig. 14). (4) Off northern Peru, westerly set was marked. The probable existence off the 

 Peruvian coast of two large anticyclonic swirls is thereby demonstrated (pp. 191-2 and 

 Fig. 63), and receives confirmation from temperature and current relationship of the 

 wedges at San Juan and Callao (p. 192, Figs, on pp. 149 and 165). The warm wedges 

 converging with the coast to the south of their respective upwelling centres appear 

 thus to be oceanic currents of compensation. 



Permmience of anticyclonic swirls 



Data of earlier observers are analysed. The agreement between (i) Schott's up- 

 welling centres and variations in volume of upwelling already noted; (2) our records of 

 drift and those, notably, of Garcia, Ray, Dinklage and Somerville; and (3) the dual 

 convergence of warm water with the coast and the counter-currents reported by the 

 'Mentor', Lavalle, and Stiglich; indicate that the anticyclonic whirls are either 

 permanent or recurrent. 



Cyclonic eddies 



Inshore counter-currents, apparently making a series of small-scale coastal eddies, 

 were frequently recorded (p. 191). At Caldera and Bahia Herradura eddies are presumed 

 to have resulted from a southward flow inshore of water deflected east, flowing in 

 compensation for a local deflection of the offshore water west. At Caldera an eddy-like 

 appearance beneath the surface was given by sinking water (Figs. 8 and 23). 



HORIZONTAL SUBSURFACE CURRENTS 



Below the surface the two layers already noted — the arm of sub-Antarctic above, and 

 the subtropical return current below — are shown to have a coastal nature which is 

 emphasized with special reference to conditions in mid-Pacific and mid-Atlantic 

 (pp. 161 , 194 and 200). The modifications they introduce into the arrangement of coastal 

 water-masses shows them to be subsurface currents compensatory for water drawn to 

 the surface by upwelling. 



SURFACE SALINITY OF THE COASTAL CURRENT 

 The fact that upwelled water has a higher salinity than the surface of the adjacent 

 ocean in the south of the region, but is less saline than the adjacent ocean in the rest of 

 the region, is attributed to these subsurface currents of compensation (pp. 162-3). 



17-2 



