Polar Exploration/Chapter 7
CHAPTER VII
PHYSICS OF THE POLAR SEAS
The first step in marine biological investigations, whether in the Polar sea or elsewhere, is the study of the physical conditions under which the marine forms of animals and plants live, and correlation of these observations in various seas. Hence the study of the physics of the oceans as a whole is most important, and it becomes the duty of a Polar explorer to carry on that research in the Polar seas. The first essential in any form of oceanic research, after knowing one's position on the earth's surface, is to know the depth, and if this has not already been determined one must take a "sounding." To be able to sound accurately in all depths is the first accomplishment of the practical oceanographer. In the Arctic Regions bathymetrical survey has been of the most irregular and piecemeal character, although on the whole we have now a fairly complete knowledge of the conformation of the floor of the North Polar Basin and the seas adjacent. Most of these soundings have been secured in the course of ordinary navigation, but Sir John Ross and his nephew took a number of soundings in a thoroughly systematic way. During recent years we have a good line of soundings across the Polar Basin taken by Nansen and Sverdrup during the drift of the Fram. The author took a large number of soundings during 1896, 1897 and 1898, on board the Windward and on board Major Andrew Coats' yacht Blencathra in the Barents Sea, from the shores of Europe to Novaya Zemlya and Franz Josef Land, and between Hope Island and Spitsbergen almost up to Wiche Islands. The Prince of Monaco and the Duke of Orleans have made series of interesting and important soundings between Spitsbergen and Greenland as far as 81° N., while Baron Nordenskjold, Leigh Smith and Makarof have sounded to the north of Spitsbergen. Amundsen, Sverdrup and others have taken soundings in the straits and sounds of the islands of the Canadian Arctic Archipelago. The most important work done by Peary during his last expedition was a series of soundings along his route to the North Pole which indicated more or less the conformation of the Polar Basin according to ideas established largely by Nansen's soundings. But it is most unfortunate that in the most important of these soundings Peary did not actually touch bottom. It would have been of more interest than any other observation that this Polar enthusiast could have taken at the North Pole, had his lead touched bottom, and had he brought back a sample of the deposit at the bottom of the sea at the Pole itself.
In the Antarctic Regions there has been a much more systematic bathymetrical survey, because, with the exception of Ross, practically no soundings were taken until the Challenger sounded in the vicinity of the Antarctic Circle off Termination Land. Before Ross, the early South Sea voyagers had no conception of deep-sea soundings. Weddell sounded in 71° 25′ S. "The water again being discoloured," says Weddell (A Voyage towards the South Pole, 1827), "we sounded with 240 fathoms of line, but got no bottom, though I am of opinion it would have been obtained at a greater length of line; but as we had no more, nor a lead sufficiently heavy, we could not be so experimental as I wished." According to the Scotia soundings there was a depth here of about 2,000 fathoms, and no doubt Weddell little guessed how much "greater length of line" he would have required to touch bottom. All the recent Antarctic expeditions have taken soundings in Antarctic and subantarctic seas, but by far the most important series taken are those of the Scotia. Altogether the Scotia took seventy-five deep soundings in the South Atlantic Ocean, and Weddell and Biscoe Seas, besides nearly five hundred soundings in the neighbourhood of the South Orkneys in water of less than 100 fathoms. Twenty-six of the seventy-five deep-sea soundings were taken south of the Antarctic Circle, and fifty were taken whilst navigating actually in the pack ice; forty-three were taken in water exceeding 2,000 fathoms, twenty-three in water exceeding 2,500—ten of the last being south of the Antarctic Circle. The deepest sounding was 2,900 fathoms, or a depth of three miles and a quarter, in 39° 27′ S., 5° 17′ E., between Gough Island and Cape Town.
The Valdivia carried out an important bathymetrical survey to the south-east of South Africa and the Challenger and the Gauss farther to the eastward. The Belgica and Pourquoi-pas? took a number of soundings from Graham Land to 124° W. between 69° and 71° S., which are of great importance, most of them being between 200 and 300 fathoms and indicative of the presence of continental land not very far to the south in these longitudes. The great interest of the Scotia soundings, along with the discovery of Coats Land, was to give an entirely new idea of the southward extension of the Weddell Sea, and to alter previous ideas of the depths of that sea which were all based on a very deep sounding taken by Ross in 68° 32′ S., 12° 49′ W., which was believed by him to be "4,000 fathoms no bottom," but which was proved by the Scotia to be 2,660 fathoms, the Buchanan sounder bringing up "blue mud." Ross's error was due to the very primitive gear he had on board for so great a depth. Instead of working with a compact machine from the ship itself, and having the valuable assistance of steam, and instead of working with apparatus that has taken sixty years to bring to its present state of perfection, this old veteran and pioneer of deep-sea exploration did wonderful work with very rude apparatus and gave us much information about ocean depths in many parts of the world. Ross did all his sounding from boats lowered for the purpose, and his hemp line was laboriously hauled in by hand on large cumbersome drums by his crew. This example of patience and endurance deserves all praise, and it would be well if it were followed in these days. Ross's line evidently sagged, after the weights had touched the bottom—if they touched at all—the line being carried away by the strong currents that exist in that region, currents which prevented the Scotia trawl from reaching bottom on three occasions in spite of extra weights being attached and a large amount of extra cable being paid out.
A theory has been advanced by Dr. H. O. Forbes (Supplementary Papers, Royal Geographical Society, 1893) that there existed at one time a land connection between New Zealand and Eastern Australia by way of the Chatham Islands and Antarctica, and also that there had been a connection between Madagascar and South America and Antarctica. The soundings of the Scotia substantially support the latter part of Forbes' theory by showing the existence of a long ridge or "Rise" (a "rise" is a ridge rising up from the bottom of the ocean to within 2,000 fathoms of the surface), about 300 miles in breadth, extending in a curve from Madagascar to Bouvet Island, and from Bouvet Island to the Sandwich Group, where there is a forked connection through the South Orkneys to Graham Land, and through South Georgia to the Falkland Islands and the South American continent. Thus Antarctica, South America and Madagascar, and probably South Africa, become connected with one another in a most direct manner by this "rise." As Dr. Pirie has pointed out, the existence of sedimentary rocks in the South Orkneys, as well as in South Georgia, points to a much greater extension of land to the southeast of South America in former times. The Scottish Expedition made another great discovery, namely, that the "Mid-Atlantic Rise" extended 1,000 miles farther south than was previously supposed, and that in all probability it connected at its southern extremity with the rise between Bouvet Island and the South Orkneys and South Georgia. This extension of the Mid-Atlantic Rise is now known as the "Scotia Rise."
These investigations tend to show a separation between the "deeps" ("deeps" are those parts of the oceans which are deeper than 3,000 fathoms) discovered by the Valdivia lying to the south-east of Bouvet Island, which may be suitably known as the "Ross Deep," and the deep lying to the south-west of South Africa, as well as that deep lying to the north of South Georgia and to the east of Argentina; all these "deeps" are separated from one another by "rises" of less than 2,000 fathoms.
The work of the Challenger, Valdivia, Gauss and Scotia in the South Atlantic and South Indian Oceans has given us a clue to the possible connections between Africa, South America and Antarctica, and now it is of great interest and importance to get more soundings to the south of Australia and New Zealand, to show more exactly what the conformation of the floor of the ocean is in those longitudes. That is one of the most important investigations for future Antarctic exploring ships to carry out.
The bathymetry of the Arctic Ocean is simple compared with that of the Antarctic Ocean, and consists of a basin almost completely surrounded by land, which does not appear to be anywhere much deeper than 2,000 fathoms, the three deepest soundings taken by Nansen and Sverdrup being 2,195 fathoms, 2,102 fathoms, and 2,020 fathoms. Unfortunately, in the three soundings these explorers took between 15° E. and 70° E., including the farthest north one, they did not succeed in reaching the bottom, these three soundings being "1,638 fathoms no bottom." Within five geographical miles of the Pole Admiral Peary obtained a sounding of "1,500 fathoms no bottom." Where the North Polar Basin is not bounded by land, as at the Behring Straits and between Spitsbergen and Greenland, it is bounded by ridges of considerably less than 2,000 fathoms in depth. The researches of the Duke of Orleans and the Mylius Erichsen Danish Expedition tend to show that a ridge covered by quite a small depth of water exists between Spitsbergen and Greenland.
A proper conception of the bathymetry of Polar seas is necessary for an adequate discussion of physical problems connected with the temperature, salinity, specific gravity and circulation, and the effect of wind, air-temperature and other phenomena that affect these seas. The physical problems of ice-covered seas are much more complicated than in seas where there is no ice, because, as we have seen previously, when the surface of the sea is being frozen over, the salt in that part of the water which is changed into ice is thrown out and must therefore make the neighbouring water more saline; on the other hand, when that ice melts during the following summer it adds a considerable amount of fresh water to the sea in its neighbourhood.
The salter water would naturally have a higher specific gravity than the fresher water but it is not unlikely that the fresher water produced from melting ice may, by virtue of its being colder than the neighbouring more saline water, actually have a higher specific gravity. The presence of icebergs, which in the south are of enormous size and very numerous, and which even in the north are very numerous in certain districts, must produce an enormous amount of fresh water during the summer and quite sufficient to affect the salinity of the sea where they occur. One of the most interesting features of Arctic waters, especially between Greenland and Spitsbergen and to the north of Spitsbergen well into the Polar Basin, is the existence of an intermediate layer of comparatively warm water in the Arctic Ocean between the surface colder water and the colder water beneath. This was observed as far back as the beginning of the nineteenth century by Scoresby and subsequently by many other observers, among whom are Admiral Markham, Maury and Leigh Smith, and in more recent years by Nansen, the Prince of Monaco, the Duke of Orleans, the author, and many others. A century ago Scoresby said, "On my first trial, made in the summer of 1810, in latitude 76° 16′ N., longitude 9° E., the temperature at the depth of 1,380 feet (230 fathoms), was found to be 33.3° (by the water brought up), whilst at the surface it was 28.8°. In nearly twenty subsequent experiments, an increase of temperature was in like manner discovered on bringing water from below, or on sending down a register thermometer to a considerable depth. In one instance (the latitude being 79° N. and longitude 5° 40′ E.) there was an increase of 7° of temperature on descending 600 feet; and in another series of experiments, near the same place, an increase of 8° was found at the depth of 4,380 feet (730 fathoms)." Recent Scandinavian observers tend to claim this as a special discovery of their own, and have omitted any reference to the work of former explorers, and in the case of one man, Benjamin Leigh Smith, this is especially ungracious.
Leigh Smith was one of the first to carry out investigations on this intermediate warm layer in a systematic manner during his cruise in Spitsbergen seas in his 80-ton schooner Sampson in 1871. Leigh Smith's observations were some of the earliest, and were most important; but, owing to his modesty, they have not been taken sufficient notice of either in Britain or abroad; Scandinavian oceanographical investigators have been especially remiss in this direction. "Honour where honour is due!" so we wish here to honour this gallant Arctic explorer—the hero of five Arctic voyages, the discoverer and cartographer of the western half of Franz Josef Land, the most remarkable leader of a band of men, whose ship was crushed in the ice off Franz Josef Land and went down in a quarter of an hour. Leigh Smith, most ably supported by Dr. W. H. Neale, afterwards wintered with his twenty-five men in an improvised hut with practically no food but bear and walrus, and during the following summer effected his own relief by conducting those twenty-five men—loyal because of their trust in him and love for him—in open boats among the Polar pack to Novaya Zemlya over a distance of 500 miles during six weeks. And, let all Scandinavian ocean physicists especially remember, that Leigh Smith was the saviour of Baron Nordenskjold's expedition of 1872–73 from starvation and death in the north of Spitsbergen, and by his good mapping the able guide of Nansen and Johansen in the last lap of their remarkable journey across the Polar Basin. Let these Scandinavians remember what Nordenskjold, the greatest of Scandinavian explorers, afterwards wrote, when the Swedish expedition had separated from Leigh Smith, namely, that "it was he who was to render it (the Swedish expedition) so great a service, and bind its members to him for ever in the bond of gratitude and attachment"; and again, when Nordenskjold says, "May we be permitted publicly to express the deep gratitude of all of us to Mr. Leigh Smith for the costly and welcome gift, and to assure him that it will be long before the members of the Swedish Polar Expedition of 1872–73 forget the Diana's visit to Mussel Bay."
It is not creditable to Britain that this most worthy and modest Englishman has never received acknowledgment of his distinguished services in Polar exploration by the Government of his own country.
This intermediate warm layer of water, at least in the region of the Greenland Sea and to the north and east of it, appears to be due to the warm water of the Gulf Stream, which, having greater density due to its salinity, dips underneath the upper colder layer, forming a distinct intermediate stratum. With all due respect to certain scientific people who deny that the Gulf Stream reaches the shores of Britain and Spitsbergen, I consider it quibbling to deny its existence and call this well-known phenomenon by some other name. Surely the finding by Torell in Spitsbergen in 1861 of the West Indian Bean Entada gigalobinum is sufficient evidence alone—call it drift, current, stream, or what you will. To the Gulf Stream is largely due the open conditions of the seas on the west of Spitsbergen, and, under certain conditions, north-eastward even to the north of Novaya Zemlya and the shores of Franz Josef Land; it also influences to a considerable extent the climate of western Europe and Britain, keeping the Norwegian fiords free of ice throughout the winter.
Relative to investigations on the influence of the Gulf Stream on the Polar Basin, is work done in what one might call a subarctic region, namely in the Faeroe Channel, during the cruises of the Lightning and Porcupine in 1868 and 1869, where the flow of the Gulf Stream is north-eastward across the ridge, between the Faeroes and Iceland. In more recent years, the Scottish Fishery Board cruisers have made additional more detailed investigations as well as the Norwegian Fishery steamer Michael Sars. Many of the most important and interesting problems regarding the physics of Arctic seas circle round the influence of the Gulf Stream.
The intermediate warm layer of water is not peculiar to the Arctic Regions. "The common feature of Antarctic water found by all expeditions," says Mr. J. Y. Buchanan, "is the thick warm layer lying between a cold layer at the surface and another cold layer at the bottom."
The intermediate warm layer in glacial seas was found by the Challenger in her Antarctic cruise. Although she was furnished only with the "Millar-Casella" thermometer, a protected maximum and minimum thermometer of the Six type, by the skilful handling of this instrument her staff was able to make a perfect thermometrical survey of the water from the surface to the depth where the maximum temperature of the first warm layer was found, which was at 200 fathoms, and to fix the superior and inferior limits to the temperature of all the water below (Challenger Report-Narrative, vol. i, Part I, p. 419).
Buchanan points out that, "One of the striking features of the ocean discovered by the Challenger expedition was the extensive area of very cold water which occupies the bottom of the sea from the east coast of South America to the ridge which runs north and south in the meridian of the island of Ascension. Here the bottom temperature was found to be 32.5° F. The existence of this exceptionally cold bottom water was discovered on the outward voyage in soundings near the Brazilian coast, so that the expedition was prepared to take up the study of it on the way home. This was done very thoroughly on a line from the mouth of the River Plate along the parallel of 35° to the meridian of Ascension. The depth of water varied from 1,900 to 2,900 fathoms, and the distribution of temperature in the water was, roughly, a warm surface layer of perhaps 100 to 200 fathoms, then a thick layer of water of temperature about 36° F. down to 1,600 fathoms near the coast, and to 2,200 fathoms or thereabouts at sea. Here was a steep temperature gradient falling away rapidly from 35° to 33° F. and more slowly to 32.5° F. The occurrence of the steep gradient shows a renewal of the water and therefore a current. The observations of the Valdivia show a similar distribution in latitude 60° to 63° S., with this difference—that the surface layer is colder than the intermediate, being about 34° F. The bottom layer has as low a temperature as 31.5° F." Unfortunately at that time there were not enough determinations of temperature of the deeper layers to indicate the gradient which separate the cold bottom water from the comparatively warm intermediate water, but now the additional observations taken on board the Scotia, Gauss and Antarctic should help to fill up the gap. The results of the extensive observations by these three expeditions will be an undoubted aid towards the solution of the meaning of this very cold water at the bottom of the ocean off the east coast of South America northward toward the equator. The lowest bottom temperatures obtained by the Scotia were 28.9° F. in 2,550 fathoms in 63° 51′ S., 41° 50′ W.; 30.95° F. in 2,547 fathoms in 64° 24′ S., 48° 18′ W.; 31.0° F. in 1,775 fathoms in 62° 10′ S., 41° 20° W.
The bottom temperatures taken by the Scotia farther south are considerably higher, and in the vicinity of where Ross thought he had "4,000 fathoms no bottom," namely, in 68° 32′ S., 12° 49′ W., the Scotia obtained a bottom temperature in 2,485 fathoms of 31.5° F.
It is very tempting to suppose that, like the Gulf Stream in the north, there is a warm highly saline current pushing southward along the surface from the Atlantic, which dips under the colder but less saline water on the surface of the Antarctic seas, and that getting cooled, this water sinks whilst abutting against the Antarctic continent, and by the ever-flowing southward upper current is pushed northward underneath along the floor of the ocean, finding its way into the deeps to the east of South America. The Scotia salinity observations also seem to support this theory, especially the record in 159 fathoms two miles off Coats Land, But this hypothesis is here given with all caution, as the results of the observations of this and the other expeditions have not yet been fully investigated.
On board the Challenger Buchanan ascertained that this exceptionally cold bottom water near the coast of South America had a very high density, and this was confirmed by the observations of the Gazelle. "It is this density at constant temperature which decides whether a water can carry its surface temperature down to great depths, or whether it shall remain at the surface, and it is the annual range of temperature of such water which gives it its penetrating power" (Proc. Royal Society, 1875, vol. clvii).
I have specially referred to this cold water at the bottom of the deep waters of the Atlantic Ocean off the South American coast as an example of the intimate connection of Antarctic phenomena with those of other parts of the world, for here the interesting question arises, How far does this cold Antarctic water flowing northward at the bottom of the Atlantic Ocean (if the conclusion is correct on the evidence we have at our disposal) not only affect the temperature, salinity and oxygenation of the waters of the Atlantic Ocean, but also, how far does it bring with it forms of Antarctic animal life, which help to populate the deep waters of the Atlantic Ocean in the vicinity of the equator? The question is an intricate one, and its solution will be largely helped by such work as the writer wishes to undertake in a second Scottish Antarctic Expedition, when an investigation of those seas which lie between the chief field of work of the Scotia, namely, the Weddell Sea, and that of the Challenger south of 40° S., is suggested as an important part of the programme.
This idea of the spread of animal life from the Poles to the equator is not new. Professor J. Arthur Thomson points out that "The generally accepted view is that the deep sea did not become a possible home of life until perhaps Cretaceous times, until the Poles cooled and the cold water rich in oxygen sank to the great depths. The affinity between abyssal animals and those found in shallower water in boreal seas has often been pointed out, and it is probable that the deep sea was largely peopled from the poles, or in any case from the shores" (The International Geography, 1907, p. 92).
That there is a strong underflowing current south of 70° S. in the vicinity of Coats Land is certain, for on three occasions the Scotia's trawl was prevented from reaching the bottom, evidently having been swept by such a current. It is not unlikely that it is the cooled intermediate layer that has sunk to the bottom which is being swept northwards towards the equator into the deep abysses of the Atlantic Ocean to the east of the South American coasts. There are many other fascinating problems of oceanic circulation that can only be solved by more extensive deep-sea research in the South Polar Regions.
There is little doubt, for instance, that there is a strong inflow of warm water between longitudes 170° E. and 180° E. where no ship has ever had any difficulty in reaching almost 78° S. Every ship that has ever tried has always been able to reach the foot of Mount Erebus and Mount Terror between these longitudes with comparative ease. Ross took the Erebus and Terror, and since then the Antarctic, the Southern Cross, the Discovery, the Morning (twice), the Terra Nova and the Nimrod have had the same experience, and now Captain Scott, doubtless with equal ease, if he sails between these longitudes, will take the Terra Nova again to McMurdo Strait without encountering any formidable pack ice. Captain Armitage has told me that on board the Discovery during her voyage southward along this route he had no ice navigation, except for a day or so in the vicinity of Cape Adare, and even that could have been avoided had he kept the vessel farther off the land. In spite of so many expeditions choosing this, the easiest route to the far south in Antarctic seas, we have not many serial sea temperature observations in these longitudes; consequently there is a fine field of work for future explorers, who are in command of well-equipped oceanographical ships, and whose programme, differing from the plans of previous expeditions to this region, is the exploration of the sea rather than the land, for this land has become specially well known owing to the splendid efforts of Scott and Shackleton.
Just as there are evidently inflows of warm water and outflows of colder water in Antarctic seas, so are there similar phenomena in Arctic seas. Reference has already been made to the Gulf Stream. One of the most marked of the cold currents is the East Greenland current, which has been known for a long time. Scoresby in 1823 pointed out that this main current along the eastern coast of Greenland "sets to the south-westward." He also pointed out a periodical offset and inset that occurred. Leigh Smith says, "Down the east coast of Greenland there is an Arctic current about 200 miles broad, bearing on its surface a mighty floating glacier, which extends to Cape Farewell, a distance of 1,400 miles. The rate of this current is variously estimated from 5 to 15 miles a day." Captain David Gray in 1874, on board the Eclipse, records: "July 24th—Found by to-day's observations that we have driven forty-three miles S. by W. half W. true, in the past three days, and that in the face of fresh winds from S.W." The drift of the crew of the Hansa, 1869–70, also furnishes concrete proof of this current.
Thanks to this current flowing right across the North Polar Basin from east to west the Fram was able to drift across. It was owing to the same current that the relics of the Jeannette, wrecked to the north of the New Siberian Islands, were carried down the east coast of Greenland round Cape Farewell, and reached Julianshaab on the west coast of Greenland three years after the wreck of the Jeannette. The latest researches on this current were those made on board the Duke of Orleans's yacht, the Belgica. These observations add very materially to our exact knowledge of this interesting phenomenon.
A similar current runs south-eastward along the coast of Labrador and brings the Polar pack down to Newfoundland considerably south of the latitude of the south of Britain. This is an excellent example of the economic importance of having an accurate understanding of the laws of oceanic circulation in the Arctic Regions and their relationship with neighbouring seas and coasts.
Antarctic deep-sea deposits (Scotia Deep-Sea Deposits, by Dr. J. H. H. Pirie, Scot. Geog. Mag., Aug. 1905) furnish very strong evidence of the existence of a large continental land-mass around the South Pole. The chief research in this direction has been done by the Challenger, the Valdivia, the Belgica, the Gauss, the Antarctic, and the Scotia, and recently by the Pourquoi-pas?. From the results of these expeditions we find that between 40° S. and 55° S. there is a broad band of globigerina ooze, with patches here and there in deeper water, far from the land, of red clay. To the south of this band there is a band of diatom ooze to which reference is made in another place. This band forms a complete circle, generally speaking, between 55° S. and 60° S. We notice, however, that the band becomes very narrow in the Drake Strait, halfway between South America and Graham Land, where it stretches only between 58° and 60° S. On the other hand, it widens out very much to the south of South Africa, where the band stretches from about 44° S. to 60° S. To the east of this it appears to dip southward in the neighbourhood of Enderby Land, but otherwise the distribution is much as has been already described. It would be of immense interest to dwell at length upon this remarkable deep-sea deposit, which is the most characteristic deposit of the Antarctic and subantarctic Regions, and which does not occur in other parts of the world except to a quite insignificant extent in certain places. To the south of this belt or band of diatom ooze we have a continuous ring south of 60° S., which is a deep-sea deposit of blue mud. In the Weddell and Biscoe Seas we have a small patch in the blue mud region which seems to be a sort of mixture of blue mud and red clay, and which is associated with the area of deep water mapped out by the Valdivia and the Scotia. A special point of interest in this blue mud deposit is found on examining maps of deposits in different parts of the world, when it is found that this deposit is always associated with continental lands. It occurs round the whole of the coasts of South and North America; round the coasts of Europe, Asia, and Africa. There is, in fact, no continental coast which is not bounded by blue mud. The natural inference, therefore, is that when we find blue mud surrounding an area of land about the South Pole that it is there in association with a great mass of continental land. It may here be mentioned that this blue mud has one character which is not common to other regions where that deposit occurs, for during the cruise of the Scotia there were taken up with the trawl many tons of subangular rocks, some of them weighing fully two to three cwts. The distribution, in the Weddell and Biscoe Seas of these great boulders, which show glacial erosion in having had their corners ground off, indicates that they have doubtless been carried out to the deep water of the Weddell Sea at the bottom of great icebergs that once formed part of, and have been calved from the great ice-sheet that probably flows northward from the South Pole over the Antarctic continent and finally break off at ice-faces bounding the Weddell and Biscoe Seas. Nothing would be more tempting than to discuss at greater length these deep-sea deposits, but that must be done at another time and in another place. Meantime the important feature to remember is the diatom ooze at the bottom of the Antarctic and subantarctic seas and the blue muds in the vicinity of all known Antarctic lands, indicating a greater extension of those lands and the existence of a great Antarctic Continent, further proof of which has already been given.