SOUNDINGS TAKEN DURING THE DISCOVERY INVESTIGATIONS, 1932-1939 71 



'congruous with the whole assemblage of rock types found in the Scotia Arc'. They are, in fact, very 

 similar to specimens from Tierra del Fuego and Clarence Island. 



Recent work close around South Georgia itself has caused only minor alterations in our previous 

 delineation of the contours of the shelf surrounding the island. On the other hand, offshore soundings 

 beyond this shelf have been of some interest, especially in a north-easterly direction. Here we have 

 found a considerable area, probably of not less than 2500 sq. miles, which is centred about 180 miles 

 from land and where a number of soundings of less than 2000 m. (1094 fm.) have been obtained. The 

 minimum depth determined here so far is 887 fm. (1622 m.), in approximately 53" 04' S, 33" 27 .1' W. 

 Altogether, eleven soundings of less than 2000 m. were obtained from two lines across this bank, 

 which for convenience of identification we shall refer to as the North-Eastern Bank. 



Directly north of Cape Crewe is another but considerably smaller area of less than 2000 m. in depth, 

 which was shown on our original chart. Recent soundings here do not materially alter the position of 

 the contours, and the connexion of this bank with the shelf around the island remains almost as 

 originally shown. 



The American bathymetric chart previously mentioned is in near agreement with our conception of 

 the connexion of this latter bank with South Georgia, but the North-Eastern Bank is shown as a major 

 feature in a ridge termed the ' South Sandwich Swell ', stretching away from South Georgia in a north- 

 easterly direction for some 700 miles. We have not, as yet, been able closely to examine all our oceanic 

 soundings in this area, but it does not appear likely that this ridge exists as shown in the American 

 chart, and the North-Eastern Bank is certainly not connected to South Georgia at a depth less than 

 1500 fm. (2743 m.); our many soundings between this bank and the island show that depths of more 

 than 3000 m. (1641 fm.) are found here over a wide area. It seems much more probable that the 

 North-Eastern Bank is part of a ridge concentric with the loop of the Scotia Arc, a ridge which also 

 includes the small area of depths less than 3000 m. (1641 fm.) immediately to the east of the bank, 

 together with another recently discovered bank in a position centred approximately on 52° 45' S, 

 24° 30' W. This latter bank was only crossed once (October 1936) and the minimum sounding was 

 1012 fm. (1851 m.) in 54° 41' 48" S, 24° 09' 54" W. It is possible that this ridge is continued to the 

 south and east, linking up with the depths of less than 4000 m. (2187 fm.) shown there in approximately 

 the latitude of 55° S; and it may even connect with the shallower area far to the south again, in a 

 position centred approximately on 60° S, 20° W. We have drawn the 4000 m. and 3000 m. contours 

 to conform with this suggestion in so far as the banks to the north-east of South Georgia are concerned 

 but, in the absence of intermediate soundings between the various banks, this interpretation must 

 remain largely hypothetical. 



If our theory is correct then, in view of the known structure of the Arc in general, and especially of 

 the prevalence of folds parallel to the main line, it appears that the shallower depths farther again to 

 the north-east (in approximately 50° S, 33° W, and from thence to approximately 47^° S, 37° W) will 

 not be connected to the North-Eastern Bank but form a further small fold also concentric with the 

 Arc proper. Much more work will be necessary before this point can be settled, but there remams 

 no doubt that the main line of the Arc lies as we originally suggested, and not through a parallel ridge 

 either north or south of South Georgia. 



SOUTH GEORGIA TO THE SOUTH SANDWICH ISLANDS 



The link between South Georgia and the Clerke Rocks was firmly established by our soundings 



prior to 1932, but the evidence in support of a connexion between the Rocks and the South Sandwich 



Group was not entirely satisfactory. Unfortunately our recent work does not provide much additional 



information. It can be seen in PI. XXIII that although several new lines of soundings were taken in 



