TEMPERATURE 141 



stations in such a turbulent neighbourhood. Streams of water may have been rising or 

 falUng across the plane of the section and may have been the cause of repeated fouling 

 of the wires used with hydrological instruments. Two of these wires are used simul- 

 taneously on one side of the ship, one forward and the other aft, for working the deep- 

 and shallow-water bottles, and they are well weighted with sinkers : the wires rarely 

 fouled one another, but on this line at St. WS 616, they were continually becoming 

 twisted round one another until eventually it was found impossible to have them both 

 working at the same time. 



Table II. Comparison of temperature, salinity and density off Colder a, June 5-6 



25-18° S: ANTOFAGASTA AND ARICA 



The hydrology of this stretch of the coast bears a resemblance to the preceding, 

 in that surface temperature was uniformly high except at Antofagasta where low tem- 

 peratures were conspicuous. The general uniformity of surface temperature may be 

 traced to warmth in the southern part of the region resulting from the northerly winds 

 already noted between the parallels of 26-30° S, and in the north to marked upwelling 

 resulting from strong inshore current. Upwelling at Antofagasta seemed in a more 

 active phase than at Caldera, since the upper layers of the highly saline return 

 current were found at the surface. In other respects temperature sections from both 

 localities agree in showing that the upwelling water was drawn mainly from the less 

 saline sub-Antarctic water; compare Figs. 22 and 23 with 24-27. 



Conditions at Antofagasta were also very changeable. After the ship had worked her 

 outward line of eight stations (Sts. WS 622-629, Figs. 24 and 26), it was necessary to 

 repeat a second line of observations (Sts. WS 630-635) on the return shorewards, this 

 time a little farther to the north owing to the drift of the ship ; for within the short 

 interval of 30 hours, the temperature, salinity and phosphate distribution had changed 

 considerably. 



On the outward journey the surface temperature inshore was about 14^ C. and did 

 not show the usual rise for some 10 miles when it suddenly jumped up 3F in 21 miles 



5-2 



