SOUNDINGS TAKEN DURING THE DISCOVERY INVESTIGATIONS, 1932-1939 95 



On the extreme eastern side of the main ridge, south of latitude 55^8 there appears to be a fairly 

 well-defined narrow crest at depths less than 1000 fm. (1829 m.), and from the information now available 

 it seems likely that this crest extends from a position a few miles south of Heard Island to the latitude 

 of 58° S, following the line of the eastern side of the main ridge. At the extreme south-eastern end of 

 the Kerguelen-Gaussberg ridge there is another well-marked shallow area, the Gribb bank (discovered 

 by the whale-catcher 'Gribb' in 1937), which appears to rise sharply in approximately 62° S, 88"" E; 

 but owing to lack of soundings on the eastern side of the ridge, between this bank and the crest 

 mentioned above, we cannot state whether Gribb bank is an isolated feature or whether it is part of 

 a possible continuation of the crest south of latitude 58° S. It seems probable, however, that Gribb 

 bank will be found to be connected with the crest and that it forms part of a shallower portion of the 

 main ridge extending from Kerguelen to the latitude of 62° S. 



The ' Discovery II ' crossed the Kerguelen-Gaussberg ridge while skirting the pack-ice from west 

 to east in April 1932, November 1935 and December 1937. Unfortunately the northern limit of the 

 ice differed only slightly on each occasion and all three crossings were consequently made within a few 

 miles of each other. In 1932 soundings were being obtained with the 'listening' type deep-water set, 

 at intervals of distance varying with the weather, but which were between 2-5 and 4-5 miles; the 

 minimum sounding was 956 fm. (1784 m.), in 56° 39-5' S, 78° 37' E. In 1935 continuous soundings 

 over a distance of 75 miles were obtained with the 'Acadia' recorder, between 57° 27-5' S, 74° 38-6' E 

 and 56° 55*2' S, 76" 46-7' E, and the minimum depth recorded was 1217 fm. (2226 m.) in 57° 047' S, 

 76° 08-7' E. Routine soundings at intervals of approximately 4 miles were then resumed, at a depth 

 of 1397 fm. (2555 m.), but the depth again shoaled and a sounding of 1044 fm. (1909 m.) was obtained 

 in 56° 32-8' S, 78° 24- 1 ' E. The deep water of the Australian-Antarctic basin was reached in 56° 59-5' S, 

 81° 23-6' E, at a depth of 2548 fm. (4660 m.). 



Continuous soundings for a distance of 275 miles were possible during the crossing of the Kerguelen- 

 Gaussberg ridge in 1937 and a zigzag course was followed between 57° 26-6' S, 74° o6-6' E and 

 56° 56-5' S, 80"^ 287' E (see Text-fig. 2c). Depths generally were less than 3000 m. (1641 fm.) over 

 the whole distance, and were under 2000 m. (1094 fm.) between 56° 53-2' S, 78° 01-2' E and 57° 18' S, 

 80° 13-2' E. The minimum sounding recorded was 910 fm. (1664 m.) in 57° 31' S, 79° 38-8' E. It will 

 be of interest, perhaps, to mention here that at the point where the 1937 line crossed the 1932 line of 

 soundings (in 56° 50' S, 77° 54-5' E) the sounding recorded in 1937 was 1164 fm. (2129 m.), which is 

 only 15 fm. (28 m.) less than the sounding of 1 179 fm. (2154 m.) obtained i-2 miles north-east of this 

 position in 1932. With the varied condition of the bottom prevailing here such agreement is gratifying. 



The recorder charts for 1935 and 1937, especially the latter, showed by the multiple echoes recorded 

 at many points that the bottom on the Kerguelen-Gaussberg ridge was extremely irregular at depths 

 greater than iioo fm. (2012 m.). At depths less than this conditions were the exact opposite; there 

 was a completely regular bottom and no signs of any multiple echoes. 



APPENDIX I 



DEEP-WATER ECHO-SOUNDING SET 

 In 1933 an ' Acadia ' type recorder was fitted to the deep-water echo-sounding set in the ' Discover)' II '. 

 This recorder, the scale of which was graduated in fathoms from 0-250, had an unlimited range, with 

 phasing by 100 fathom steps: i.e. it was possible to ' step-back ' or 'step-on' the transmissions so that 

 the echo would always appear on the record. The principle of this recorder was quite simple: a trans- 

 mission was sent out by the hammer normally at every complete revolution of the phasing switch. 



