114 DISCOVERY REPORTS 



shown that the surface water close against the South American coast is hydrologically 

 different from water which may also share northerly movement hundreds of miles out 

 to sea, and consequently provides a distinct biological environment. There is, however, 

 no sharp boundary between the two waters, the one merging gradually into the other. 

 Moreover, from the dynamic standpoint it appears that the movement of both waters 

 is actuated by similar principles, only in the one the presence of the coast induces 

 upwelling and other modifications. In view of the emphatic differences in the character 

 of the inshore and offshore components, it is desirable to draw a distinction between the 

 two. The cool surface water close against the South American coast will be termed the 

 Peru Coastal Current : and for contrast, the adjacent oceanic drift which, lying to the west 

 of this, also seems to share northerly movement, the name Peru Oceanic Current is sug- 

 gested. As, however, both currents compose the eastern limb of the anticyclonic 

 circulation, and as no sharp boundary exists between them, they may jointly be referred 

 to by the name Peru Current. Such definition of the Peru Current would not be in- 

 consistent with the Peru Current of Schott and the Peruvian Current of Sverdrup. 



The Peru Coastal Current has great variability, and counter-currents involving 

 southerly and easterly drift have sometimes been reported within its boundaries: not, 

 however, as a permanent feature, and with the exception of the Mentor Current of 

 Berghaus and of El Nino, they have not been given names. Grounds are adduced in a 

 subsequent section for believing that such counter-currents may form a permanent 

 system of inshore and offshore eddies. 



THE WORK OF THE 'CARNEGIE' 



The cruises of the ' Carnegie ', extending in many directions across the eastern South 

 Pacific, form a valuable supplement to our own observations, which had of necessity to 

 be near the coast. They cover the area westwards of the South American coast to the 

 meridian of 115° W, and from the equator to the 40th parallel south, and give for the 

 first time a modern account of the water layers at and below the surface from which it is 

 possible to determine the bathymetric limits of the Peru Oceanic Current. Thus the 

 ' Carnegie's ' observations, though made in 1928-9, two years before those of the ' William 

 Scoresby ', give a picture of the general oceanic conditions without which a study of the 

 coastal current by itself would lack perspective. 



Sverdrup (1931) illustrates with salinity sections the relation between the Peru 

 Current and the intermediate Antarctic current (Antarctic intermediate water), which 

 he shows to be characteristic of the entire southern Pacific. The intermediate Antarctic 

 current is shown to be a layer of low salinity at about 600-1000 m., which gains in depth 

 and gains in salinity as it flows towards the north. The Peru Current, on the other hand, 

 is shown to be a surface current whose depth does not exceed 300 m., and whose flow 

 represents the eastern limb of an anticyclonic movement which is illustrated schemati- 

 cally by a figure taken from Johnstone (1923). 



Sverdrup observes that three of the sections, from Sts. 40-45, 70-80, and 60-50, run 



