become available it is impossible to speak definitely as to the normal distribution of monthly temperature throughout the year, for even at the same station in consecutive years the months vary greatly Thus at Snow Hill (65° S.) the mean temperature of August 1903 was 13·5° higher than that of August 1902, though June had been 7° colder, and at the “Discovery’s” winter quarters July 1903 was 13° colder than July 1902 though June was 2° warmer, August having exactly the same mean temperature in each year. The mean temperature of the year is evidently higher in the position of the “Belgica’s” drift than in Victoria Land at the same latitude; but it is noticeable that on the west side of Graham Land, where Charcot wintered, the average mean temperature was (taking the average of his two wintering) 15° higher than on the east side, where Noidenskjold wintered in nearly the same latitude. The observations, however, were not synchronous, and it may not be right to compare them. We may perhaps say that along the whole of the known Antarctic coasts the temperature in the two midsummer months is within a degree or two of 32° F., and varies little from place to place or from year to year; but in the winter months the temperature is lower as the latitude increases and is subject to great variations from place to place and from year to year. It seems quite possible that at no place in the Antarctic region do the mean monthly sea-level winter temperatures fall so low as in the Arctic poles of cold, but data regarding winter temperatures in the interior are lacking. All the complete yearly series of temperature show that the winter six months from April to September have a low and nearly equal temperature, there being a very abrupt fall in February and March, and an equally abrupt rise in October and November. The warmest day experienced at the “Discovery’s” winter quarters had a mean temperature of 34·7°, and the coldest −45·7°, the extreme range of daily temperature being thus 80·4°.
The absolutely lowest temperature recorded in the Antarctic region was −66·8° on a journey southward from the “Discovery’s” winter quarters by Lieut. Barne on the 15th of September 1903, the lowest temperature at the winter-quarters was −58·5° on the 28th of September 1903. On Sir Ernest Shackleton’s expedition the lowest temperature was −57°; but no other expedition met temperatures lower than −45·6° on the “Belgica,” −43·1° at Cape Adare, and −41·4° on the “Gauss.” Sudden rises of temperature during storms are common in the Antarctic region, from whichever quarter the wind blows. During the ascent of Mt Erebus the temperature was found to fall as the height increased from 0° F. at sea-level to −24° at 5000 ft.; it remained stationary to 8600 ft., fell to −28° at 10,650 ft., and then rose to −22° at 11,500 ft., and fell a few degrees at the summit. It might appear as if the “isothermal layer” of the upper atmosphere had been reached at a remarkably low elevation; but the temperature variations may also be explained by differences in the temperature of the strong air currents which were passed through.
Pressure and Winds.—The normal fall of pressure southward, which gives rise to the strong westerly winds of the roaring forties, appears to be arrested about 65° S., and to be succeeded by a rise of pressure farther south. This view is supported by the frequency of south-easterly winds in the neighbourhood of the Antarctic Circle reported by all explorers, and the hypothesis of a south polar anticyclone or area of high pressure over the Antarctic continent has gained currency in advance of any observations to establish it. The complete data of Sir Ernest Shackleton’s expedition are not available at the time of writing, but the yearly mean pressure as recorded at the “Discovery’s” winter-quarters was 29·35 in. for 1902, and 29·23 in. for 1903. At Cape Adare it was 29·13 in. for 1899, in the “Belgica” 29·31 in. for 1898, and in the “Gauss” 29·13 in. for 1902. These figures, so far as they are comparable, show distinctly higher pressures in the higher latitudes, and the wind observations bear out the inference of a south-polar high pressure area, as at the “Discovery’s” winter-quarters 80% of the winds had an easterly component, and only 3% a westerly component. It is bewildering, however, to find that on the sledge journeys there was an equally marked preponderance of wind with a westerly component, and in discussing the result in the published records of the expedition Mr R. H. Curtis, of the Meteorological Office, felt compelled to ask whether the correction for variation of the compass (in that region about r45°) was possibly omitted in the case of the sledge journeys. The “Gauss” observations and those at Cape Adare bore out the frequency of easterly winds, and on the “Scotia” it was observed that practically all of the easterly winds met with were to the south of the Antarctic Circle. The “Belgica” found rather more westerly than easterly winds in her drift; easterly winds predominating in summer, westerly winds in winter. At Cape Royds Shackleton found easterly winds to predominate, the most frequent direction being south-east; but on the great southern journey, south-south-east winds prevailed, occasionally swinging round to south-south-west, and even at the farthest south (88° S.) the ridges into which the snow was blown, 10,000 ft. above the sea, showed that south-southeasterly winds predominated. On the journey to the Magnetic Pole Professor David found that along the coast the prevailing winds were south-westerly, with occasional blizzards from the south-east, but he noticed that the westerly winds were of the nature of a land breeze, springing up soon after midnight and continuing to blow fresh until about 10 a.m. Thus the balance of probability inclines towards the hypothesis of a south-polar high-pressure area. An upper current of air blowing from a north-westerly direction was usually indicated by the clouds and smoke on Mt Erebus, and on the occasion of a great eruption, when the steam column reached more than 20,000 ft. above the sea it entered a still higher stratum of wind blowing from the south-east.
The intensity of the blizzards is worthy of remark, for the velocity of the wind often reached 40 or even 60 m. an hour, and they were usually accompanied by a rapid rise of temperature.
Observations of sunshine made at the “Discovery’s” winter quarters yielded many records of continuous sunshine extending throughout 24 consecutive hours. and in the summer months about 50% of the possible sunshine was often recorded, the maximum being 490 hours, or 66% of the total possible for December 1903. Thus, although the sun was above the horizon only for 246 days, it shone sufficiently to yield more than 1725 hours of bright sunshine for the year, an amount exceeded in few parts of England, where the sun may shine on 365 days. The intensity of solar radiation in the clear weather of the Antarctic makes it feel exceedingly hot even when the air temperature is far below the freezing point. There is a great difference between the clear skies of 78° S. and the extremely frequent fogs which shroud the coast near the Antarctic Circle and render navigation and surveying exceedingly difficult. Heavy snowstorms are frequent on the coast, but inland during the snow blizzards it is impossible to say whether the whirling snow-dust is falling from the air or being swept from the ground. Professor David is inclined to believe that the surface of the snow-plains is being lowered more by the action of the wind sweeping the snow out to sea than it is raised by precipitation, the total amount of which appears to be very small.
Flora and Fauna.—Recent expeditions have discovered that, despite the low temperature of the summer, in which no month has a mean temperature appreciably above the freezing point, there are on the exposed Antarctic land patches of ground with a sparse growth of cryptogamic vegetation consisting of mosses, lichens, fungi and fresh-water algae. The richest vegetation discovered on the “Nimrod” expedition consisted of sheets of a lichen or fungoid growth, covering the bottom of the fresh-water lakes near Cape Royds, and visible through the clear ice throughout the many months when the water is frozen. No flowering plants occur within the Antarctic Circle or in the immediately adjacent lands.
The marine fauna is very rich and abundant. All the expeditions obtained many new species, and the resemblance which occurs between many of the forms and those which inhabit
