84 DISCOVERY REPORTS 



MARION AND PRINCE EDWARD ISLANDS 



(Marion Island, 46° 49' S, 37° 49' E; 



Prince Edward Island, 46° 36' S, 37° 57' E) 



In April 1935, the 'Discovery II' visited Marion and Prince Edward Islands, and during a partial 

 examination of the group continuous soundings were taken over a period of 10 hr., representing 

 a distance over the bottom of approximately 65 miles. The track of the ship during this work is shown 

 in Text-fig. 3^/, p. 46. 



The islands appear to lie on a submarine plateau and are steep-to, with considerable slopes from 

 seawards at certain points; the maximum depth recorded over the distance of 12 miles between the 

 two islands was 142 fm. (260 m.). South of the south-west corner of Marion Island the sounding was 

 896 fm. (1639 '^O ^^ ^ distance of 3-5 miles from land, which is equivalent, approximately, to a slope 

 of 14°. From this position, on a course almost parallel to the south coast of the island, soundings 

 shoaled steadily to a depth of 174 fm. (318 m.) in a position 3 miles south of the south-east corner of 

 the island. This coastal shelf appears to extend for at least 3 miles east of Marion Island, but its full 

 extent was not determined. 



East of Prince Edward Island the bottom is irregular and there are some very steep slopes. At one 

 point, parallel to the coast at East Cape, the depth increased from 19 to 197 fm. (35 to 360 m.) in 

 0-5 miles, which is equivalent to an average slope of I9|°; the major portion of this slope, however, 

 was at an angle of 28°. 



BOUVET ISLAND 

 (54° 26' S, 3° 24' E) 



During a series of cruises from Cape Town in 1938-9 further soundings were obtained at Bouvet 

 Island on two occasions. Altogether, continuous soundings totalled lof hr. and covered about 80 miles 

 of the sea bed. As we had already suspected from the soundings taken here in October 1930 during 

 a running survey and the search for Thompson Island (Herdman, 1932), the bottom was found to be 

 very confused and irregular at depths less than 1300 fm. (2377 m.). There is a sharp rise (in one instance 

 at an angle of approximately 20°) to a narrow submarine shelf of about 2 miles in width, from which 

 the island itself rises fairly steeply. A section of the continuous sounding record taken in 1938, when 

 approaching the island from the north, is shown in PI. XXIX, fig. i, and provides ample proof of the 

 varied bottom in this neighbourhood. 



MAGELLAN STRAIT 



Between November 193 1 and November 1934, the 'Discovery II' made eight passages through 

 Magellan Strait, but only on three occasions was the passage by way of the main channel throughout. 

 The Cockburn Channel entrance to the western part of the main strait was used three times (October 

 1932, March and November 1934) and the entrance by Otway Bay and Sea Shell or Abra Channel 

 once (December 1933). In October 1934 another route from the main strait to the Cockburn Channel 

 was examined ; this was by way of Pedro Sound, the Ackwalisnan Canal and Dynely Sound. 



In December 1933 the 'Acadia' recorder unfortunately was out of action, but a full series of 

 soundings was obtained at intervals of about 4 min. with the ' listening' sets, through Otway Bay and 

 Sea Shell or Abra Channel. In March 1934 we were still without the recorder, but a good series of 

 depths was determined over the whole length of the Cockburn Channel and into the main strait. In 

 October of the same year the ' Acadia ' recorder was again in use and we were able to obtain a continuous 

 record over a period of io|- hr. during the passage from the main channel to sea via the Ackwalisnan 

 Canal. On our return a month later the recorder was used for a total of 14 hr. and continuous soundings 

 obtained from a position 55° 27' S, 73° 40' W to the main strait, via the Cockburn Channel. 



