230 DISCOVERY REPORTS 



Lucas soundings by the 'Discovery', 'William Scoresby', 'Pourquoi PasP'^ and 

 ' Antarctic ' .- The positions of soundings taken by the vessels of the Discovery Committee 

 are shown in black — those of other vessels as circles. The combined results give a good 

 general idea of the bottom relief of this area. 



When considering the contours of the bathymetric chart (Plate XLVII) in detail, it will 

 be seen that there are two separate depressions, a small one with a maximum depth of 

 1371 m. lying south of Snow Island, and the main depression which stretches from 

 Deception Island almost to Clarence Island. The eastern end of the latter has a consider- 

 able area with a depth of over 2000 m., the maximum found by the ' Discovery II ' being 

 2879 m., but the western end is on the whole much shallower. Here there is only one 

 small area over 2000 m., with a maximum of 2085 m. found by the ' William Scoresby' 

 in February 1 929. The remainder of the depression has an average depth of 1 500-1 600 m. 



The slope on the northern side of the main depression is fairly steep along the whole 

 length, but on the northern side of the South Shetlands and the Shetlands — Elephant 

 Island ridge the bottom falls away quite gently. This may be compared with the South 

 Sandwich Islands ridge and the Deep beyond it, which has already been described, though 

 the drop from the South Shetlands to the Bransfield depression is not so sharp and the 

 depression not nearly so deep. Geologically, however, it would appear that both may 

 have been formed in the same manner. Three lines of our echo soundings and one of the 

 'Meteor's' place the average distance of the 1000 in. contour about 40 miles from the 

 centre line of the South Shetlands on the northern side and 10 miles on the southern. 



More soundings are required in the depression in the neighbourhood of Bridgman 

 Island in order to determine the position of the 1000 m. contour. Bridgman Island is 

 certainly volcanic and is regarded by Holtedahl ^ as " the remains of a much larger volcanic 

 mass which has been to a large extent planed down by marine abrasion". It seems 

 probable, therefore, that it was once part of the South Shetlands and that there is 

 comparatively shallow water between it and King George Island. There is only one 

 sounding in the vicinity, 620 m., taken by the ' Pourquoi Pas? ', and on this and on the 

 geological evidence we think it probable that the 1000 m. contour lies to the south of the 

 island. The position of Bridgman Island appears to be rather similar to that of Deception 

 Island, between which and Livingston Island a submarine plateau exists. 



Unfortunately there are only two lines of echo soundings running north and south 

 between King George and Elephant Islands, but these, together with a Lucas sounding 

 midway between them, show the probable existence of a ridge. Ferguson, who was 

 unable to land on Elephant Island, has suggested* that some of the darker stratified rocks 

 may be bedded lavas. This would appear to be an error, and Wordie,^ who collected 



' Deux. Exped. Fran. (1908-10), Cartes, No. xi (1912). 

 " Swed. Sild-Pol. Exped. (1901-3), i, Lief 2, Karte (1917). 

 ^ Holtedahl, loc. cit., supra, pp. 97-8. 

 * Ferguson, Trans. Roy. Soc. Edin., Liii, p. 35 (1925). 



'' Wordie, Shackleton Antarctic Expedition, 1914-17, Geological Observations in the Weddell Sea Area, 

 Trans. Roy. Soc. Edin., liii, p. 27 (1925). 



