SOUNDED AND UNSOUNDED AREAS 



Plates 19, 20, 21, 22, 23 



The accompanying charts showing the sounded 

 and unsounded areas of sea bottom are based upon 

 charts prepared by the United States Hydrographic 

 Office. Several years ago that office published five 

 charts, one each for the north and south Atlantic, 

 one each for the north and south Pacific, and one 

 for the Indian Ocean, on which were shown the 

 sounded and unsounded areas in the three oceans. 

 These charts were intended to guide United States 

 Naval vessels, equipped with sonic-sounding ap- 

 paratus, in compljdng with instructions that when 

 practicable their courses be laid across unsounded 

 areas, so as gradually to complete surveys of the 

 ocean bottom for bottom configuration. The sup- 

 plemental information, much of it not yet published, 

 that had been assembled in connection with this 

 report has been added to the charts already drawn. 

 It is hoped that these charts represent with fair 

 accuracy what has been done in ascertaining the 

 configuration of the sea bottom, and that they may 

 serve to guide ves.sels of other countries, as well as 

 those of the United States, to these areas on which 

 there is inadequate information. 



It is pertinent here to refer to the article. "The 

 bathymetric soundings of the oceans," by Lt. Com. 

 H. Bencker, published by the International Hydro- 

 graphic Bureau, June 1930, and presented at the 

 meeting in Stockholm of the Section of Physical 

 Oceanography, International Union of Geodesy and 

 Geophysics, August 1930. This paper, in addition 

 to a general account of the growth of knowledge 

 of the bathymetry of the oceans, contains five 

 appendices, one of which is "Chronological list of 

 oceanic explorations from the year 1800," and 

 another is "List arranged by oceans, of principal 

 oceanic deeps." 



Mention may be made of converting the sound 

 intervals of echo soundings into true depths. Data 

 on subsurface temperatures and salinities in the 

 oceans are now becoming so extensive that the time 

 is ripe for a revised edition of the British Admiralty's 

 "Tables of the velocity of sound in pure water and 

 sea water for use in echo-sounding and sound-rang- 

 ing," published in 1927. Tho.se institutions that 



have acquired pertinent data would render meri- 

 torious service to oceanography by cooperating with 

 the British Admiralty in perfecting that valuable 

 publication. It should be practicable to deduce 

 almost instantaneously the true depth from the 

 echo time-interval. 



A glance at the accompanying charts shows that 

 for the more general features the north Atlantic and 

 the north Pacific have been mostly, but not entirely, 

 covered. Recently, largely because of the activities 

 of the Meteor and Discovery II, knowledge 

 of the south Atlantic has been greatly increased, but 

 the lines of soundings north of latitude 50°S. are 

 still so far apart that only the outlines of the grosser 

 features may be surely recognized. Exploration of 

 Antarctic waters has been intensely prosecuted 

 since 1925 by the Discovery II and William 

 ScoRESBY, and, beginning somewhat later, by Dis- 

 covery I and NoRWEGiA. So many additional lines 

 have been run that it should now be possible to 

 construct a new bathymetric chart for the seas 

 around Antarctica, south of about 50°S. latitude. 

 There are also lines from Antarctica to southern 

 Africa, .southern Australia, New Zealand, and 

 southern South America. The Mabahiss has 

 recently, 1933, greatly added to knowledge of the 

 northwestern Indian Ocean, as shown in an article 

 by Wiseman and Sewell.' Other important recent 

 work on the bathymetry of the Pacific comprises 

 new bathymetric charts of the South China Sea by 

 the Institut Oceanographique de ITndochine, of the 

 seas adjacent to Japan by the Hydrographic De- 

 partment of Imperial Japanese Navy, of Philippine 

 waters by the Philippine Coast and Geodetic Survey, 

 and of the Netherlands East Indies by the Snellius 

 Expedition. The last mentioned charts constitute 

 one of the finest publications on bottom topography 

 ever is.sued.'- Plate 1, composed of two sheets, is a 

 colored bathymetric chart of the eastern part of the 



' Wiseman, J. H. D., and Sewell, R. B. S., The floor of the 

 Arabian Sea: Geolog. Mag., vol, 74, pp. 219-230, pi. 11, 

 May, 1937. 



2 van Riel, P. M., Bottom configuration in relation to the 

 flow of the bottom water: Snellius Expedition, vol. 2, 

 Oceanographic Results, part 2, chapter 2, pp. 63, 6 pis., 16 

 detailed charts, 1934. 



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