8 DISCOVERY REPORTS 



a submarine ridge between Clarence and Joinville Islands, with the saddle-depth a short 

 distance south of the former island. Many more soundings in this area are necessary 

 before the bottom contours at the northern end of the strait can be drawn accurately. 

 For a more detailed description of the soundings in the Bransfield Strait reference 

 should be made to the paper on soundings by H. F. P. Herdman (1932). 



Thus the Bransfield Strait consists of two basins enclosed by shelves of the South 

 Shetland Islands, Elephant and Clarence Islands, Graham Land and Trinity Peninsula 

 and by submarine ridges at either end of the strait. The effect of these ridges is to 

 restrict the horizontal circulation of the water masses which lie below the depth of the 

 confining ridges. 



Fig. 3. Temperature-salinity diagrams for Sts. WS 400, WS 384 and WS 385. 



Before discussing the hydrology of the Bransfield Strait and the manner in which 

 it is influenced by the topography of the sea-bottom, the following comparison of con- 

 ditions inside and outside the strait will be of service. For this purpose three stations 

 from February 1929 have been selected: St. WS 400 situated in 62 07' S, 62 33' W, 

 i.e. in the Drake Passage just north of the Bransfield Strait, and Sts. WS 384 and 

 WS 385, situated both at the north-east end of the strait in 62 25' 40" S, 58 06' 10" W 

 and 62 32' S, 57 55' W respectively. The temperature and salinity data from these 

 stations have been plotted in Fig. 3 as temperature-salinity diagrams. The figures on 

 the curves represent the depths in metres of the observations. 



In the Antarctic Zone of the South Atlantic Ocean the water masses may be divided 

 into three layers. The uppermost consists of Antarctic surface water, the middle layer 



