74 DISCOVERY REPORTS 



current — can on the average be traced as far south as 49° S. A close examination of the 

 data shows, however, that the terminal region of the current is one of very irregular 

 movements; the current changes with the wind, and streams of subtropical water 

 alternate, in varying positions, with areas of sub-Antarctic water. Under such con- 

 ditions there is no fixed boundary between the two waters; their limits appear to be 

 capable of rapid variation, and there are also areas of mixed water. The mean tempera- 

 ture chart shows that water with the temperature which is usually found on the 

 northern side of the subtropical convergence, where it is well defined, reaches an average 

 latitude of 43-44 S. 



The subtropical water from the southern end of the Brazil current and the sub- 

 Antarctic water which flows round Cape Horn from the Pacific Ocean, flow together 

 first towards the north-east and then eastwards across the Atlantic Ocean. In spite of 

 the fact that they flow in almost the same direction, the two waters retain to a large 

 extent their distinctive properties, and the rather scanty data available points to the 

 existence of a sharp convergence between them (see pp. 57, 59). 



The majority of the Atlantic current charts, probably beginning with that of Peter- 

 mann (1865), show that the easterly current turns sharply northwards in the eastern 

 half of the ocean, and the Benguela current — the northward current along the west 

 coast of Africa — is represented as a northward branch of the West Wind Drift. The same 

 view was taken in the previous year by Miihry (1864, pp. 34-5), who regarded the low 

 temperature of the water off the west coast of Africa as evidence of the existence of a 

 northward current similar to that which had previously been found off the west coast of 

 South America. The most recent investigation of the surface currents of the Atlantic 

 Ocean made by Meyer (1923) shows very clearly, however, that the Benguela current is 

 not a continuation of the West Wind Drift, but is separated from it by a well-marked 

 convergence. Meyer's chart shows that although the sub-Antarctic part of the eastward 

 current bends towards the north in the eastern half of the ocean, it reaches no farther 

 than 28 S. The temperature and salinity distribution in this part of the ocean (Figs. 8, 

 1 1 , and Schott, 1926, pi. x) suggests that the northward movement is even less, and there 

 are sufficient data to show that the sub-Antarctic water has a well-defined boundary 

 which does not extend north of 37 S (Fig. 4). The fact that there is a continuous belt 

 of subtropical water across this region, curving southwards from the subtropical region 

 of the Atlantic Ocean to join with that of the Indian Ocean, shows that the older current 

 charts in particular have exaggerated the northward movement of the West Wind Drift. 



The temperature and salinity distribution also suggests that some of the subtropical 

 water which flows eastwards across the Atlantic Ocean is possibly deflected southwards 

 near the Cape of Good Hope to mix with the water which turns back from the Agulhas 

 current in an easterly movement across the Indian Ocean. This suggestion finds no 

 support from the current charts of Michaelis (1923) and Meyer (1923), but it is in agree- 

 ment with the very early chart made by Rennell in 1832. Both Michaelis and Meyer 

 agree, however, with the conclusion first reached by Rennell that some of the water 

 from the Agulhas current flows westwards round Cape Point into the Atlantic Ocean. 



