74 DISCOVERY REPORTS 



500 m. (273 fm.); the minimum sounding was 373 m. (204 fm.) in 60° 53' S, 37° 13' W. Continuing 

 to the north-east for a distance of about 35 miles the hne of soundings then crossed the bank found on 

 the northerly run earlier in the year. Agreement with the previous results was good and it was found 

 that the hitherto isolated depth of 543 m. (297 fm.) could be linked up with a larger area. Four depths 

 of less than 1000 m. (547 fm.) were determined on this north-east line and these included one of 

 488 m. (267 fm.), in 60° 17' S, 35° 48' W, roughly 9 miles east-by-north of the earlier sounding of less 

 than 500 m. 



From here the course still lay to the north-east, to the longitude of 35° 20' W, where it became 

 possible to turn east. Shortly after turning, and about 20 miles from the previous bank, another area 

 with depths less than 1000 m. (547 fm.) was located. In all, seventeen soundings were obtained here 

 and the minimum depth was 667 m. (365 fm.), in 62° 02-5' S, 34° 41' W. A number of these soundings 

 were taken in a small area at the extreme eastern end of this bank, but it has not been possible to show 

 all of them owing to the small scale of our bathymetric chart. 



Not much farther to the east more shallow soundings were met with. Here ten depths of less than 

 1000 m. (547 fm.) were obtained over a distance of about 40 miles, the least being 602 m. (329 fm.), 

 in 60'' 00-5' S, 32° 30' W. 



Between these last two shallow areas there exists a small gap, to which we have already referred in 

 our general discussion on the Scotia Arc. Only one sounding of more than 3000 m. was obtained here 

 (3807 m. (2082 fm.)), in 60° 03-5' S, 33° 33' W; the three remaining depths in the gap were approxi- 

 mately 1000 m. less. 



The traverse of the ridge continued east from the 40-mile bank for about 30 miles. Unfortunately, 

 the ice began to trend in a northerly direction here and we were thus prevented from obtaining 

 soundings over the remaining distance of no miles to Southern Thule. The line now was directed in 

 general to the north-east, towards Montagu Island, but the soundings obtained were of considerable 

 value in the determination of the 3000 m. contour. 



There still remains a wide area east of the South Orkney shelf where, so far as we are aware, no 

 soundings have yet been obtained, > and there is also the gap to the west of Southern Thule. However, 

 despite the lack of evidence from soundings in these areas, there can now be little doubt that the banks 

 discovered in 1932 form part of a well-marked connexion between the South Sandwich Islands and 

 the South Orkneys. Further evidence is provided by the indications of considerable folding at the 

 western end of the portion of the ridge just described. Here, between the meridians 36'' W and 

 38° W, is a complicated bottom of varying depths, such as is a common feature in other parts of the 

 Arc. Steep slopes are prevalent and we have one instance, in approximately 61° 10' S, 35° 03' W, 

 where a slope of 13° occurred between two soundings nearly 7 miles apart. 



SOUTH ORKNEYS TO CLARENCE ISLAND AND THE SOUTH SHETLANDS 

 In our earlier report we stated that from the geological evidence then available the South Orkney 

 Islands did not appear to form an integral part of the Scotia Arc, although soundings indicated that 

 they were almost certainly a link in the chain. In January 1933 the 'Discovery II' made a running 

 survey of the islands, and in the course of the work rock samples were collected from seven localities 

 (Sts. 1089-1095) widely distributed among the group. These specimens were examined by Tilley 

 (1935), who reported that in their general relationships they bear a striking similarity to rocks from the 

 South Shetlands. 



1 Three soundings of less than 2000 m. (1094 fm.) were obtained by the 'Walter Rau' between 60° 15' and 60° 25' S, and 

 in 39° to 39° 30' W, which suggest that the 2000 m. (1094 fm.) contour on the northern side of the ridge should lie considerably 

 north of the tentative line we have proposed in PI. XXOL The depths concerned are given as 1700, 1700 and 1800 m. (930, 

 930 and 985 fm.). 



