236 DISCOVERY REPORTS 



Seiche action 



The question of distinguishing between upwelling and subsidence on the one hand, 

 and seiche action on the other, is considered. Definite evidence of the existence of 

 seiches in the Pacific has not been found, but the possibiUty that our results may lend 

 themselves to this interpretation is pointed out (p. 212). 



Latitude 



No disparity of upwelling was noted between the Chilean and Peruvian coasts, although 

 the surface layers are more homogeneous, and the current is stronger off Peru. An agent 

 equalizing these factors is possibly the diff'erential eflFect of latitude (p. 211). Neither 

 sea-bottom contour nor coast-line trend appeared to have any effect (pp. 202-4). 



Sinking of newly mixed water 



The essential differences between the sinking of water by this mechanism and by 

 subsidence are considered (p. 214). The process seemed to have been in progress off 

 Caldera on the outer edge of the upwelling zone, and to have been brought on by 

 recent northerly wind (p. 140). It is presumed to have far-reaching importance in the 

 mixing of upper and lower layers and to occur most frequently in the neighbourhood 

 of the subtropical convergence. 



DISTRIBUTION OF WATER MASSES 



Surface 



The convergence of sub-Antarctic and subtropical water which lies along the 30- 

 32° S parallels in 95-105° W, curves northwards on approaching the Chilean coast and 

 was found as far north as 24-26° S, in 70-71° W (Table V and Fig. 42, pp. 160 and 161). 

 As both these water-masses participate in its northward flow, the Peru Coastal Current 

 crosses a convergence. 



Beneath the surface 



At this convergence, the sub-Antarctic water sinks and is shown to send an arm north- 

 wards for some 10° of latitude beneath the subtropical layer (p. 1 61 and Fig. 42) ; and was 

 welling up to the surface at three localities (Figs. 20, 22 and 43). At a deeper level, a 

 more saline and comparatively warm return current of subtropical water (poor in 

 oxygen) was drawn southwards, and was welling up to the surface at San Juan, 

 Antofagasta, and possibly Cape Carranza, centres of exceptional activity (pp. 162-3, 

 Figs. 18, 24 and 45). 



HORIZONTAL SURFACE CURRENTS 



Highly saline tropical water (> 36-00 °l^^) was not met within the limits of the 

 Coastal Current, but a highly saline wedge of warm water lay at some distance off the 

 coast both off southern and northern Peru (Figs. 16 and 63). Continuity in a counter- 

 current just here is not easily explained : the depth of its maximum salinity is shown to 



