SOUNDINGS TAKEN DURING THE DISCOVERY INVESTIGATIONS, 1932-1939 63 



will be noticed that at the southern end it narrows considerably. The distance between the 7000 m. 

 contours at the northern end varies between 17 and 30 miles, whereas south of latitude 57° S the 

 Trench gradually narrows from 15 to 4 miles in width between the same contours. It would have 

 been of the greatest interest if continuous soundings could have been taken across the Trench with 

 the recorder, but on no occasion was this possible. Four lines of soundings were run across it after 

 the recorder had been fitted (in 1934 (2), 1936 and 1937), but on the two earlier crossings (a zigzag, or 

 double crossing in April 1934, between the latitudes of 58° S and 59° 31' S) the instrument was out 

 of action, and on the later crossings, at the extreme northern and southern ends, bad weather precluded 

 records from such great depths. 



50 



60 



70 



60 



50 



40 



30 



20 



Fig. II. Key chart showing positions of profiles in Fig. 12. 



Another interesting feature of the soundings since 1932 is the discovery that the Burdwood Bank is 

 separated from the main Falkland-Patagonian shelf by much deeper water than was formerly supposed. 

 Eight additional lines of soundings were taken between the Burdwood Bank and the Falkland Islands 

 and these have resulted in a marked change in the contours of this area (see p. 68). 



It is now possible to construct four new profiles of the bottom in the area comprising the Scotia 

 Sea and Arc (Text-fig. 11). Two of these cross the Scotia Sea from north to south and the remaining 

 two run in east-south-easterly and south-easterly directions respectively from South Georgia. One of 

 these (Text-fig. 12a), in approximately 45° W, extends for 620 miles and comprises 160 soundings. 

 It crosses the well-defined ridge west of the Shag Rocks, illustrates the extensive folding on the 

 northern side of the South Orkney Islands and shows the southward continuation of the South Orkney 

 shelf to approximately 62° S. It should also be noted that the bottom just south of the Burdwood 

 Bank-Shag Rocks ridge is likewise an area of considerable folding. The second cross-section (Text- 

 fig. 12 d), which is based on 107 soundings, runs from Cape Pembroke, Falkland Islands, to a position 

 in line with, but slightly east of, Clarence Island, a distance of 575 miles. It shows some similar 

 characteristics in that an area of considerable folding exists south of the Burdwood Bank — more 



