88 DISCOVERY REPORTS 



The facts do not, however, justify this conclusion ; the sudden decrease in the tem- 

 perature and salinity of the current is probably due to the fact that it climbs steeply 

 towards the surface over the colder and less saline Antarctic bottom water ; with such a 

 sudden variation of its path the properties of the current are certain to be affected to a 

 marked degree by vertical mixing. It is also not safe to assume that the movement of 

 the deep water will be directed exactly along the line of the contours of the isobaric 

 surface ; there is such a close relation where the currents are horizontal and steady, but 

 in the region under discussion, where the vertical movements are pronounced, and the 

 currents are not free from acceleration, the existence of a component of movement 

 towards the south across the contours is not unlikely. 



The distribution of temperature, salinity, and oxygen content in sections 4 a and 4 

 (Plates V, VI), north of South Georgia and north-west of the South Sandwich Islands, 

 indicates that the North Atlantic deep current flows at least as far south as South Georgia. 

 The high temperature, salinity, and oxygen content of the deep water at Sts. 1054-6 in 

 50 S are typical of the North Atlantic current, and water with such a high salinity could 

 have no other origin. The sections also show that the change in the properties of the 

 deep layer between 50 S and South Georgia is no greater than that which may 

 reasonably be regarded as caused by the climbing of the layer, and although some of 

 the deep water may belong to a current from the west, the temperature and salinity dis- 

 tributions give no clear indication of it ; there seems to be no water whose properties 

 are appreciably different from those of the Atlantic water. The slope of the isotherms 

 and isohalines downwards to the north is some indication of a current towards the 

 east, but it may, however, be largely the result of the climbing of the deep water to the 

 south and the sinking of the cold surface and bottom waters towards the north. In 

 the neighbourhood of the continental slope north of South Georgia there is a small slope 

 of the isotherms and isohalines downwards to the south which suggests the existence 

 of a small movement towards the west. 



The observations in section 4, north-west of the South Sandwich Islands, indicate 

 that the North Atlantic deep current climbs towards the south as far as 52-53 S without 

 interruption ; its last traces may reach a still higher latitude, but the rapid decrease of 

 temperature, increase of oxygen content and the changes of salinity south of 53 S 

 suggest that the deep water belongs chiefly to a current from another source. The pro- 

 perties of this water are such as might result from the mixing of the North Atlantic 

 water with Antarctic bottom water, but the charts in Figs. 19-22 suggest that it belongs 

 to a current flowing from the southern and eastern parts of the Scotia Sea. 



The temperature and salinity distribution in the deep layer in the western part of the 

 Scotia Sea shows that the current flows mainly east and south, but in the eastern part 

 the deep water appears to follow the curve of the Scotia Arc, turning towards the north 

 to flow out of the sea as a cold deep current. The temperature and salinity distribution 

 in sections 4 and 4 a shows that some of it sinks into the bottom layer below the North 

 Atlantic current, but the charts in Figs. 19-22 indicate that it also turns towards the east 

 round the northern end of the South Sandwich group. It then eddies back to the south 



