152 



DISCOVERY REPORTS 



geneity is shown in both temperature and saUnity in the upper 200 m. at these four 

 localities (compare Figs. 32 and 36-38 with Figs. 44 and 46-48), and is probably 

 attributable to progressive vertical mixture resulting from increased current off northern 

 Peru. Thus the Peru Coastal Current gains immensely in breadth towards its northern 



end. 



As the latitude of this section of the coast is lower than those previously examined, 

 there is a natural rise in the general level of the surface temperature and salinity. 

 A surface temperature of i6-oo° C, that off Salaverry, is the lowest inshore temperature 

 recorded in this region: in the wedge of warm water the temperature reaches 20-60° C. 



Fig. 35. Changes in wind and in the distribution of surface isotherms off the Guaiiape Islands in the period 

 July 9-1 1, 1931. Symbols as in Fig. 28. Station positions may be identified by collation with Fig. 13. The 

 dotted lines show the shift of the isotherms of 18, 19 and 20° C. (see Table IV). 



The region of the Guanape Islands and Salaverry was examined in two states of the 

 wind within a very short time (Fig. 35). In the evening of July 9, St. WS 674 was worked 

 at 56 miles from land in winds of S 35" E with force 1-3 to 5-8 m.p.h. From this position 

 the ship ran to Salaverry during the night, taking a record of surface temperature as she 

 went (Table IV and Fig. 30). On the following night the ship worked a line of stations 

 outwards from the Guafiape Islands back towards the position of St. WS 674. In the 

 meantime the wind direction had changed from south-south-east to south-south-west 

 with force 1-2 m.p.h., and all isotherms at 20 miles to sea and upwards were now found 

 closer inshore. The greatest displacement was over the middle of the shelf some 30 miles 



