March 3. 1898] 



NATURE 



421 



It is not likely that any living land-fauna will be discovered 

 on the Antarctic continent away from the penguin rookeries. 

 Still, an Antarctic expedition will certainly throw much light on 

 many geological problems. Fossil finds in high latitudes are 

 always of special importance. The pieces of fossil wood from 

 Seymour Island can hardly be the only relics of plant life that 

 are likely to be met with in Tertiary and even older systems 

 within the Antarctic. Tertiary, Mesozoic, and Palaeozoic forms 

 are tolerably well developed in the Arctic regions, and the 

 occurrence of like forms in the Antarctic regions might be ex- 

 pected to suggest much as to former geographical changes, such 

 as the extension of the Antarctic continent towards the north, 

 and its connection with, or isolation from, the northern con- 

 tinents, and also as to former climatic changes, such as the 

 presence in pre-Tertiary times of a nearly uniform temperature 

 in the waters of the ocean all over the surface of the globe. 



Magnetic and Pendulum Observations, Geodetic Measure- 

 ments, Tides and Currents. 



In any Antarctic expedition magnetic observations would, of 

 course, form an essential part of the work to be undertaken, 

 and the importance of such observations has been frequently 

 dwelt upon by eminent physicists and navigators. Should a 

 party of competent observers be stationed at Cape Adare for 

 two years, pendulum observations could be carried out there and 

 at other points within the Antarctic, or even on icebergs and 

 on the interior ice-cap. It might be possible to measure a degree 

 on the Antarctic continent or ice-cap, which would be a most 

 useful thing to do. By watching the motions of the icebergs 

 and ice from land at Cape Adare, much would be learnt about 

 oceanic currents, and our knowledge of the tides would be in- 

 creased by a systematic series of tidal observations on the shores 

 of Antarctica, where we have at present no obsersations. The 

 series of scientific observations here mentioned, and others that 

 might be indicated, would fill up many gaps in our knowledge of 

 the physical conditions of these high southern latitudes. 



Depth of the Antarctic Ocean. 



In regard to the depth of the ocean immediately surrounding 

 the Antarctic continent we have at present very meagre inform- 

 ation, and one of the objects of an Antarctic expedition would 

 be to supplement our knowledge by an extensive series of 

 soundings in all directions throughout the Antarctic and 

 Southern Oceans. It <\ould in this way be possible, after a care- 

 ful consideration of the depths and marine deposits, to trace out 

 approximately the outlines of the Antarctic continent. At the 

 present time we know that Ross obtained depths of lOO to 500 

 fathoms all over the great bank extending to the east of Victoria 

 Land, and somewhat similar depths have been obtained extend- 

 ing for some distance to the east of Joinville Island. Wilkes 

 sounded in depths of 500 and 800 fathoms about twenty or 

 thirty miles off Adelie Land. The depths found by the Chal- 

 lenger in the neighbourhood of the Antarctic circle were from 

 130010 1800 fathoms, and further north the Challenger soxxndixx^^i 

 ranged from 1260 to 2600 fathoms. To the south-west of South 

 Georgia, Ross paid out 4000 fathoms of line without reaching 

 bottom. In the charts of depth which I have constructed, I 

 have always placed a deep sea in this position ; for it appears 

 to me that Ross, who knew very well how to take soundings, 

 was not likely to have been mistaken in work of this kind. 



The few indications which we thus possess of the depth of the 

 ocean in this part of the world seem to show that there is a 

 gradual shoaling of the ocean from very deep water towards 

 the Antarctic continent, and, so far as we yet know, either from 

 soundings or temperature observations, there are no basins cut 

 off from general oceanic circulation by barriers or ridges, similar 

 to those found towards the Arctic. 



Deposits of the Antarctic Ocean. 



The deposits which have been obtained close to the Antarctic 

 continent consist of blue mud, containing glauconite, made up 

 for the most part of detrital matters brought down from the land, 

 but containing a considerable admixture of the remains of pelagic 

 and other organisms. Further to the north there is a very pure 

 diatom ooze, containing a considerable quantity of detrital matter 

 from icebergs, and a few pelagic foraminifera. This deposit 

 appears to form a zone right round the earth in these latitudes. 

 Still further to the north the deposits pass in deep water, either 

 into a Globigerina ooze, or into a red clay with manganese 

 nodules, sharks' teeth, ear-bones of whales, and the other 



NO. [479, VOL. 57] 



materials characteristic of that deep-sea deposit. Since these 

 views, however, as to the distribution of deep-sea deposits 

 throughout these high southern latitudes, are founded upon re- 

 latively few samples, it cannot be doubted that further samples 

 from different depths in the unexplored regions would yield 

 most interesting information. 



Temperature of the Antarctic Ocean. 



The mean daily temperature of the surface waters of the Ant- 

 arctic, as recorded by Ross, to the south of latitude 63" S. in the 

 summer months, varies from 27*3° to 33*6°, and the mean of all 

 his observations is 29-85°. As already stated, his mean for the 

 air during the same period is somewhat lower, being 2874". In 

 fact, all observations seem to show that the surface water is 

 warmer than the air during the summer months. 



The Challenge! observations of temperature beneath the 

 surface indicate the presence of a stratum of colder water 

 wedged between warmer water at the surface, and warm water 

 at the bottom. This wedge- shaped stratum of cold water ex- 

 tends through about 12° of latitude, the thin end terminating 

 about latitude 53° S., its temperature varying from 28° at 

 the southern thick end to 32*5° at the northern thin end, 

 while the temperature of the overlying water ranges from 29" in 

 the south to 38° in the north, and that of the underlying water 

 from 32° to 35°. This must be regarded as the distribution of 

 temperature only during the summer, for it is improbable that 

 during the winter months there is a warmer surface layer. 



In the greater depths of the Antarctic, as far south as the 

 Antarctic circle, the temperature of the water varies between 

 32° and 35° F., and is not, therefore, very different from the 

 temperature of the deepest bottom water of the tropical regions 

 of the ocean. The presence of this relatively warm water 

 in the deeper parts of the Antarctic Ocean may be explained 

 by a consideration of general oceanic circulation. The warm 

 tropical waters which are driven southwards along the eastern 

 coasts of South America, Africa, and Australia into the great 

 all encircling Southern Ocean, there become cooled as they are 

 driven to the east by the strong westerly winds. These waters, 

 on account of their high salinity, can suffer much dilution with 

 Antarctic water, and still be denser than water from these higher 

 latitudes at the same temperature. Here the density observations 

 and the sea -watergases indicate that a large part of the cold water 

 found at the greater depths of the ocean probably leaves the sur- 

 face and sinks towards the bottom in the Southern Ocean, between 

 the latitudes of 45° and 56° S. These deeper, but not neces- 

 sarily bottom, layers are then drawn slowly northwards towards 

 the tropics, to supply the deficiencies there produced by evapor- 

 ation and southward-flowing surface currents, and these deeper 

 layers of relatively warm water appear likewise to be slowly 

 drawn southwards to the Antarctic area to supply the place of 

 the ice-cold currents of surface water drifted to the north. 

 This warm underlying water is evidently a potent factor in 

 the melting and destruction of the huge table topped icebergs 

 of the southern hemisphere. While these views as to circulation 

 of oceanic water appear to be well established, still a fuller ex- 

 amination is most desirable at different seasons of the year, with 

 improved thermometers and sounding machines. Indeed, all 

 deep-sea apparatus has been so much improved as a result of 

 the Challenger explorations, that the labour of taking salinity 

 and all other oceanographlcal observations has been very much 

 lessened. 



Pelagic Life of the Antaixtic Ocean. 



In the surface waters of the Antarctic there is a great abun- 

 dance of diatoms and other marine algae. These floating banks 

 or meadows form primarily not only the food of pelagic 

 animals, but also the food of the abundant deep sea life which 

 covers the floor of the ocean in these south polar regions. 

 Pelagic animals, such as copepods, amphipods, molluscs, and 

 other marine creatures, are also verj' abundant, although species 

 are fewer than in tropical waters. Some of these animals seem 

 to l)e nearly, if not quite, identical with those found in high 

 northern latitudes, and they have not been met with in the inter- 

 vening tropical zones. The numerous species of shelled 

 Pteropods, Foraminifera, Coccoliths, and Rhabdoliths, which 

 exist in the tropical surface waters, gradually disappear as we 

 approach the Antarctic circle, where the shelled Pteropods are 

 represented by a small Limacina, and the Foraminifera by only 

 two species of Globigerina, which are apparently identical with 

 those in the Arctic Ocean. A peculiarity of the tow-net gather- 

 ings made by the Challenger Expedition in high southern 



