DESCRIPTION OF THE ISLANDS 343 



it was not until 1909 that Suess^ suggested that the lines of folding lay along the path 

 of this island chain which, by analogy with a similar structure in the northern hemi- 

 sphere, later writers have called the South Antillean Arc, a name recently superseded 

 by the more appropriate if less familiar one of the Scotia Arc.^ Suess's theory was 

 contested on the grounds that the Andean aifinities exhibited by the igneous rocks of 

 Graham Land and the western portion of the South Shetlands were entirely lacking 

 throughout the rest of the chain, and that no continuous submarine connection existed 

 to link up the several islands which compose it ; but the controversy that arose, although 

 based on careful geological observation in many parts of the arc, was insufficiently 

 supported by soundings, so that the argument on both sides was inconclusive. By 

 the use of echo sounding machines, however, many further soundings have now been 

 obtained, first by the 'Meteor' in 1925-6, and later, between 1930 and 1932, by the 

 R.R.S. 'Discovery II'. As a result of these soundings, particularly those of the 

 ' Discovery II ' which ran to many thousands, Herdman was able to show that whatever 

 their geological significance ridges exist throughout all the sectors of the arc and link 

 up the land fragments of which it is composed. 



The submarine connection varies greatly in accentuation. It is least definite along the 

 northern arm of the island loop in the big oceanic gaps which separate the South Sand- 

 wich Islands from the Gierke Rocks, and the Shag Rocks from the Burdwood Bank. 

 Along the southern arm a much more pronounced ridging has been demonstrated, 

 most marked as far as we are at present aware between the South Orkneys and 

 Glarence Island, where at certain points the sea-floor rises to within 500 m.^ of the 

 surface. Between the South Orkneys and the South Sandwich Islands there is 

 evidence that the connecting ridge is also a pronounced one, but here, perhaps more 

 than in any other sector of the arc, many more soundings are needed before the exact 

 nature of the connection can be adequately understood. The earliest evidence of any 

 connection is from the soundings taken by the 'Scotia'* between 1903 and 1904, 

 when Bruce demonstrated that the coastal shelf of the South Orkneys extended 

 for seventy-five miles east by south of Laurie Island, and farther eastward obtained 

 soundings of slightly over 1000 m. in about 32° W, west by south of Southern Thule 

 in the South Sandwich Islands. More convincing evidence was produced in 191 1, 

 when the ' Deutschland ' found a substantial rise in 37° W about midway between 

 the shallow soundings of the 'Scotia'. Owing to the northerly out-thrusting of the 

 Weddell Sea ice between the South Orkneys and the South Sandwich group the 

 ' Discovery II ' was unable to obtain soundings in this sector of the arc until her return 

 from the Weddell Sea in January 1932, when she found a very pronounced ridge in 

 36° W and between 60° and 61° S with a minimum sounding of only 543 m. From the 



1 Suess, E., 1909, Das Ajttlitz der Erde, ui, 2, p. 558. 



^ A name proposed by Mr J. M. Wordie and employed by Herdman in 1932. 

 ^ Herdman, H. F. P., 1932, loc. cit., pp. 227-9. 



* See Bruce, W. S., 1905, Bathymetric Survey of the South Atlantic Ocean and Weddell Sea, Scott. Geog. 

 Mag., XXI, No. VIII, pp. 404-8. 



