By B. J. Birkeland

On account of the improvised character of the South Polar Expedition, the meteorological department on the Fram was not so complete as it ought to have been. It had not been possible to provide the aerological outfit at the time of sailing, and the meteorologist of the expedition was therefore left behind in Norway. But certain things were wanting even to complete the equipment of an ordinary meteorological station, such as minimum thermometers and the necessary instructions that should have accompanied one or two of the instruments. Fortunately, among the veterans of the expedition there were several practised observers, and, notwithstanding all drawbacks, a fine series of observations was obtained during ten months' stay in winter-quarters on the Antarctic continent. These observations will provide a valuable supplement to the simultaneous records of other expeditions, especially the British in McMurdo Sound and the German in Weddell Sea, above all as regards the hypsometer observations (for the determination of altitude) on sledge journeys. It may be hoped, in any case, that it will be possible to interpolate the atmospheric pressure at sea-level in all parts of the Antarctic continent that were traversed by the sledging expeditions. For this reason the publication of a provisional working out of the observations is of great importance at the present moment, although the general public will, perhaps, look upon the long rows of figures as tedious and superfluous. The complete working out of these observations can only be published after a lapse of some years.

As regards the accuracy of the figures here given, it must be noted that at present we know nothing about possible alterations in the errors of the different instruments, as it will not be possible to have the instruments examined and compared until we arrive at San Francisco next year. We have provisionally used the errors that were determined at the Norwegian Meteorological Institute before the expedition sailed; it does not appear, however, that they have altered to any great extent.

The meteorological outfit on the Fram consisted of the following instruments and apparatus:

Three mercury barometers, namely:

One normal barometer by Fuess, No. 361 . One Kew standard barometer by Adie, No. 889. One Kew marine barometer by Adie, No. 764.

Five aneroid barometers:

One large instrument with thermometer attached, without name or number. Two pocket aneroids by Knudsen, Copenhagen, one numbered 1,503. Two pocket aneroids by Cary, London, Nos. 1,367 and 1,368, for altitudes up to 5,000 metres (16,350 feet). Two hypsometers by Casella, with several thermometers.

Mercury thermometers:

Twelve ordinary standard (psychrometer-) thermometers, divided to fifths of a degree (Centigrade). Ten ordinary standard thermometers, divided to degrees. Four sling thermometers, divided to half degrees. Three maximum thermometers, divided to degrees. One normal thermometer by Mollenkopf, No. 25.

Toluene thermometers:

Eighteen sling thermometers, divided to degrees. Three normal thermometers-by Tounelot, No. 4,993, and Baudin, Nos. 14,803 and 14,804. Two torsion hair hygrometers of Russeltvedt's construction, Nos. 12 and 14. One cup and cross anemometer of Professor Mohn's construction, with spare cross. One complete set of precipitation gauges, with Nipher's shield, gauges for snow density, etc.

Registering instruments:

Two barographs. Two thermographs. One hair hygrograph. A number of spare parts, and a supply of paper and ink for seven years.

In addition, various books were taken, such as Mohn's "Meteorology," the Meteorological Institute's "Guide," psychrometric tables, Wiebe's steam-pressure tables for hypsometer observations, etc.

The marine barometer, the large aneroid, and one of the barographs, the four mercury sling thermometers, and two whole-degree standard thermometers, were kept on board the Fram, where they were used for the regular observations every four hours on the vessel's long voyages backwards and forwards.

As will be seen, the shore party was thus left without mercury sling thermometers, besides having no minimum thermometers; the three maximum thermometers proved to be of little use. There were also various defects in the clockwork of the registering instruments. The barographs and thermographs have been used on all the Norwegian Polar expeditions; the hygrograph is also an old instrument, which, in the course of its career, has worked for over ten years in Christiania, where the atmosphere is by no means merciful to delicate instruments. Its clockwork had not been cleaned before it was sent to the Fram, as was done in the case of the other four instruments. The barographs worked irreproachably the whole time, but one of the thermographs refused absolutely to work in the open air, and unfortunately the spindle pivot of the other broke as early as April 17. At first the clockwork of the hygrograph would not go at all, as the oil had become thick, and it was not until this had been removed by prolonged severe heating (baking in the oven for several days) that it could be set going; but then it had to be used for the thermograph, the mechanism of which was broken, so that no registration was obtained of the humidity of the air.

The resulting registrations are then as follows: from Framheim, one set of barograms and two sets of thermograms, of which one gives the temperature of the air and the other the temperature inside the house, where the barometers and barograph were placed; from the Fram we have barograms for the whole period from her leaving Christiania, in 1910, to her arrival at Buenos Aires for the third time, in 1912.

Of course, none of these registrations can be taken into account in the provisional working out, as they will require many months' work, which, moreover, cannot be carried out with advantage until we have ascertained about possible changes of error in the instruments. But occasional use has been made of them for purposes of checking, and for supplying the only observation missing in the ten months.

The meteorological station at Framheim was arranged in this way: the barometers, barograph, and one thermograph hung inside the house; they were placed in the kitchen, behind the door of the living-room, which usually stood open, and thus protected them from the radiant heat of the range. A thermometer, a hygrometer, and the other thermograph were placed in a screen on high posts, and with louvred sides, which stood at a distance of fifteen yards to the south-west of the house. A little way beyond the screen, again, stood the wind-vane and anemometer. At the end of September the screen had to be moved a few yards to the east; the snow had drifted about it until it was only 2 1/2 feet above the surface, whereas it ought to stand at the height of a man. At the same time the wind-vane was moved. The screen was constructed by Lindström from his recollection of the old Fram screen.

The two mercury barometers, the Fuess normal, and the Adie standard barometer, reached Framheim in good condition; as has been said, they were hung in the kitchen, and the four pocket aneroids were hung by the side of them. All six were read at the daily observations at 8 a.m., 2 p.m., and 8 p.m. The normal barometer, the instructions for which were missing, was used as a siphon barometer, both the mercury levels being read, and the bottom screw being locked fast; the usual mode of reading it, on the other hand, is to set the lower level at zero on the scale by turning the bottom screw at every observation, whereupon the upper level only is set and read. The Adie standard barometer is so arranged that it is only necessary to read the summit of the mercury. It appears that there is some difference between the atmospheric pressure values of the two instruments, but this is chiefly due to the difficult and extremely variable conditions of temperature. There may be a difference of as much as five degrees (Centigrade) between the thermometers of the two barometers, in spite of their hanging side by side at about the same height from the floor. On the other hand, the normal barometer is not suited to daily observations, especially in the Polar regions, and the double reading entails greater liability of error. That the Adie barometer is rather less sensitive than the other is of small importance, as the variations of atmospheric pressure at Framheim were not very great.

In the provisional working out, therefore, the readings of the Adie barometer alone have been used; those of the normal barometer, however, have been experimentally reduced for the first and last months, April and January. The readings have been corrected for the temperature of the mercury, the constant error of the instrument, and the variation of the force of gravity from the normal in latitude 45º. The reduction to sea-level, on the other hand, has not been made; it amounts to 1.1 millimetre at an air temperature of -10º Centigrade.

The observations show that the pressure of the atmosphere is throughout low, the mean for the ten months being 29.07 inches (738.6 millimetres). It is lower in winter than in summer, July having 28.86 inches (733.1 millimetres), and December 29.65 inches (753.3 millimetres), as the mean for the month, a difference of 20.2 millimetres. The highest observation was 30.14 inches (765.7 millimetres) on December 9, and the lowest 28.02 inches (711.7 millimetres) on May 24, 1911; difference, 54 millimetres.

Air Temperature and Thermometers.

As has already been stated, minimum thermometers and mercury sling thermometers were wanting. For the first six months only toluene sling thermometers were used. Sling thermometers are short, narrow glass thermometers, with a strong loop at the top; before being read they are briskly swung round at the end of a string about half a yard long, or in a special apparatus for the purpose. The swinging brings the thermometer in contact with a great volume of air, and it therefore gives the real temperature of the air more readily than if it were hanging quietly in the screen.

From October 1 a mercury thermometer was also placed in the screen, though only one divided to whole degrees; those divided to fifths of a degree would, of course, have given a surer reading. But it is evident, nevertheless, that the toluene thermometers used are correct to less than half a degree (Centigrade), and even this difference may no doubt be explained by one thermometer being slung while the other was fixed. The observations are, therefore, given without any corrections. Only at the end of December was exclusive use made of mercury thermometers. The maximum thermometers taken proved of so little use that they were soon discarded; the observations have not been included here.

It was due to a misunderstanding that mercury thermometers were not also used in the first half-year, during those periods when the temperature did not go below the freezing-point of mercury (-89º C.). But the toluene thermometers in use were old and good instruments, so that the observations for this period may also be regarded as perfectly reliable. Of course, all the thermometers had been carefully examined at the Norwegian Meteorological Institute, and at Framheim the freezing-point was regularly tested in melting snow.

The results show that the winter on the Barrier was about 19.º C. (21.6º F.) colder than it usually is in McMurdo Sound, where the British expeditions winter. The coldest month is August, with a mean temperature of -44.5º C. (-48.1º F.); on fourteen days during this month the temperature was below -50º C. (-58º F.). The lowest temperature occurred on August 13: -58.5º C. (-73.3º F.); the warmest day in that month had a temperature of -24º C. (-11.2º F.).

In October spring begins to approach, and in December the temperature culminates with a mean for the month of -6.6º C. (+2O.lº F.), and a highest maximum temperature of -0.2º C. (+31.6º F.). The temperature was thus never above freezing-point, even in the warmest part of the summer.

The daily course of the temperature -- warmest at noon and coldest towards morning -- is, of course, not noticeable in winter, as the sun is always below the horizon. But in April there is a sign of it, and from September onward it is fairly marked, although the difference between 2 p.m. and the mean of 8 a.m. and 8 p.m. only amounts to 2º C. in the monthly mean.

Humidity of the Air.

For determining the relative humidity of the air the expedition had two of Russeltvedt's torsion hygrometers. This instrument has been accurately described in the Meteorologische Zeitschrift, 1908, p. 396. It has the advantage that there are no axles or sockets to be rusted or soiled, or filled with rime or drift-snow.

Fig. 1.

Fig. 2.

Fig. 3.

The two horsehairs (h, h') that are used, are stretched tight by a torsion clamp (Z, Z', and L), which also carries the pointer; the position of the pointer varies with the length of the hairs, which, again, is dependent on the degree of humidity of the air. (See the diagrams.) These instruments have been in use in Norway for several years, especially at inland stations, where the winter is very cold, and they have shown themselves superior to all others in accuracy and durability; but there was no one on the Fram who knew anything about them, and there is therefore a possibility that they were not always in such good order as could be wished. On September 10, especially, the variations are very remarkable; but on October 13 the second instrument, No. 12, was hung out, and there can be no doubt of the correctness of the subsequent observations.

It is seen that the relative humidity attains its maximum in winter, in the months of July and August, with a mean of 90 per cent. The driest air occurs in the spring month of November, with a mean of 73 per cent. The remaining months vary between 79 and 86 per cent., and the mean of the whole ten months is 82 per cent. The variations quoted must be regarded as very small. On the other hand, the figures themselves are very high, when the low temperatures are considered, and this is doubtless the result of there being open water not very far away. The daily course of humidity is contrary to the course of the temperature, and does not show itself very markedly, except in January.

The absolute humidity, or partial pressure of aqueous vapour in the air, expressed in millimetres in the height of the mercury in the same way as the pressure of the atmosphere, follows in the main the temperature of the air. The mean value for the whole period is only 0.8 millimetre (0.031 inch); December has the highest monthly mean with 2.5 millimetres (0.097 inch), August the lowest with 0.1 millimetre (0.004 inch). The absolutely highest observation occurred on December 5 with 4.4 millimetres (0.173 inch), while the lowest of all is less than 0.05 millimetre, and can therefore only be expressed by 0.0; it occurred frequently in the course of the winter.

Precipitation.

Any attempt to measure the quantity of precipitation -- even approximately -- had to be abandoned. Snowfall never occurred in still weather, and in a wind there was always a drift that entirely filled the gauge. On June 1 and 7 actual snowfall was observed, but it was so insignificant that it could not be measured; it was, however, composed of genuine flakes of snow. It sometimes happened that precipitation of very small particles of ice was noticed; these grains of ice can be seen against the observation lantern, and heard on the observer's headgear; but on returning to the house, nothing can be discovered on the clothing. Where the sign for snow occurs in the column for Remarks, it means drift; these days are included among days of precipitation. Sleet was observed only once, in December. Rain never.

Cloudiness.

The figures indicate how many tenths of the visible heavens are covered by clouds (or mist). No instrument is used in these observations; they depend on personal estimate. They had to be abandoned during the period of darkness, when it is difficult to see the sky.

Wind.

For measuring the velocity of the wind the expedition had a cup and cross anemometer, which worked excellently the whole time. It consists of a horizontal cross with a hollow hemisphere on each of the four arms of the cross; the openings of the hemispheres are all turned towards the same side of the cross-arms, and the cross can revolve with a minimum of friction on a vertical axis at the point of junction. The axis is connected with a recording mechanism, which is set in motion at each observation and stopped after a lapse of half a minute, when the figure is read off. This figure denotes the velocity of the wind in metres per second, and is directly transferred to the tables (here converted into feet per second).

The monthly means vary between 1.9 metres (6.2 feet) in May, and 5.5 metres (18 feet) in October; the mean for the whole ten months is 3.4 metres (11.1 feet) per second. These velocities may be characterized as surprisingly small; and the number of stormy days agrees with this low velocity. Their number for the whole period is only 11, fairly evenly divided between the months; there are, however, five stormy days in succession in the spring months October and November.

The frequency of the various directions of the wind has been added up for each month, and gives the same characteristic distribution throughout the whole period. As a mean we have the following table, where the figures give the percentage of the total number of wind observations:

N. N.E. E. S.E. S. S.W. W. N.W. Calm.

1.9 7.8 31.9 6.9 12.3 14.3 2.6 1.1 21.3

Almost every third direction is E., next to which come S.W. and S. Real S.E., on the other hand, occurs comparatively rarely. Of N., N. W., and W. there is hardly anything. It may be interesting to see what the distribution is when only high winds are taken into account -- that is, winds with a velocity of 10 metres (32.8 feet) per second or more. We then have the following table of percentages:

N. N.E. E. S.E. S. S.W. W. N.W.

7 12 51 10 4 10 2 4

Here again, E. is predominant, as half the high winds come from this quarter. W. and N.W. together have only 6 per cent.

The total number of high winds is 51, or 5.6 per cent. of the total of wind observations.

The most frequent directions of storms are also E. and N.E.

The Aurora Australis.

During the winter months auroral displays were frequently seen -- altogether on sixty-five days in six months, or an average of every third day -- but for want of apparatus no exhaustive observations could be attempted. The records are confined to brief notes of the position of the aurora at the times of the three daily observations.

The frequency of the different directions, reckoned in percentages of the total number of directions given, as for the wind, will be found in the following table:

N. N.E. E. S.E. S. S.W. W. N.W. Zenith.

18 17 16 9 8 3 8 13 8

N. and N.E. are the most frequent, and together make up one-third of all the directions recorded; but the nearest points on either side of this maximum -- E. and N.W. -- are also very frequent, so that these four points together -- N.W., N., N.E., E. -- have 64 per cent. of the whole. The rarest direction is S.W., with only 3 per cent. (From the position of the Magnetic Pole in relation to Framheim, one would rather have expected E. to be the most frequent, and W. the rarest, direction.) Probably the material before us is somewhat scanty for establishing these directions.

Meteorological Record from Framheim.

April, 1911 -- January, 1912.

Height above sea-level, 36 feet. Gravity correction, .072 inch at 29.89 inches. Latitude, 78º 38' S. Longitude, 163º 37' W.

Explanation of Signs in the Tables.

SNOW signifies snow.

MIST ,, mist.

AURORA ,, aurora.

RINGSUN ,, large ring round the sun.

RINGMOON ,, ,, ,, moon.

STORM ,, storm

sq. ,, squalls

a. ,, a.m.

p. ,, p.m.

I., II, III., signify respectively 8 a.m., 2 p.m., and 8 p.m.

º (e.g., SNOWº) signifies slight.

2 (e.g., SNOW2) ,, heavy.

Times of day are always in local time.

The date was not changed on crossing the 180th meridian

Provisional Remarks on the Examination of the Geological Specimens Brought by Roald Amundsen's South Polar Expedition from the Antarctic Continent (South Victoria Land and King Edward VII. Land). By J. Schetelig, Secretary of the Mineralogical Institute of Christiania University

The collection of specimens of rocks brought back by Mr. Roald Amundsen from his South Polar expedition has been sent by him to the Mineralogical Institute of the University, the Director of which, Professor W. C. Brögger, has been good enough to entrust to me the work of examining this rare and valuable material, which gives us information of the structure of hitherto untrodden regions.

Roald Amundsen himself brought back altogether about twenty specimens of various kinds of rock from Mount Betty, which lies in lat. 85º 8' S. Lieutenant Prestrud's expedition to King Edward VII. Land collected in all about thirty specimens from Scott's Nunatak, which was the only mountain bare of snow that this expedition met with on its route. A number of the stones from Scott's Nunatak were brought away because they were thickly overgrown with lichens. These specimens of lichens have been sent to the Botanical Museum of the University.

A first cursory examination of the material was enough to show that the specimens from Mount Betty and Scott's Nunatak consist exclusively of granitic rocks and crystalline schists. There were no specimens of sedimentary rocks which, by possibly containing fossils, might have contributed to the determination of the age of these mountains. Another thing that was immediately apparent was the striking agreement that exists between the rocks from these two places, lying so far apart. The distance from Mount Betty to Scott's Nunatak is between seven and eight degrees of latitude.

I have examined the specimens microscopically.

From Mount Betty there are several specimens of white granite, with dark and light mica; it has a great resemblance to the white granites from Sogn, the Dovre district, and Nordland, in Norway. There is one very beautiful specimen of shining white, fine-grained granite aplite, with small, pale red garnets. These granites show in their exterior no sign of pressure structure. The remaining rocks from Mount Betty are gneissic granite, partly very rich in dark mica, and gneiss (granitic schist); besides mica schist, with veins of quartz.

From Scott's Nunatak there are also several specimens of white granite, very like those from Mount Betty. The remaining rocks from here are richer in lime and iron, and show a series of gradual transitions from micacious granite, through grano-diorite to quartz diorite, with considerable quantities of dark mica, and green hornblende. In one of the specimens the quantity of free quartz is so small that the rock is almost a quartz-free diorite. The quartz diorites are: some medium-grained, some coarse-grained (quartz-diorite-pegmatite), with streaks of black mica. The schistose rocks from Scott's Nunatak are streaked, and, in part, very fine-grained quartz diorite schists. Mica schists do not occur among the specimens from this mountain.

Our knowledge of the geology of South Victoria Land is mainly due to Scott's expedition of 1901 -- 1904, with H. T. Ferrar as geologist, and Shackleton's expedition of 1907 -- 08, with Professor David and R. Priestley as geologists. According to the investigations of these expeditions, South Victoria Land consists of a vast, ancient complex of crystalline schists and granitic rocks, large extents of which are covered by a sandstone formation ("Beacon Sandstone," Ferrar), on the whole horizontally bedded, which is at least 1,500 feet thick, and in which Shackleton found seams of coal and fossil wood (a coniferous tree). This, as it belongs to the Upper Devonian or Lower Carboniferous, determines a lower limit for the age of the sandstone formation. Shackleton also found in lat. 85º 15' S. beds of limestone, which he regards as underlying and being older than the sandstone. In the limestone, which is also on the whole horizontally bedded, only radiolaria have been found. The limestone is probably of older Palæozoic age (? Silurian). It is, therefore, tolerably certain that the underlying older formation of gneisses, crystalline schists and granites, etc., is of Archæan age, and belongs to the foundation rocks.

Volcanic rocks are only found along the coast of Ross Sea and on a range of islands parallel to the coast. Shackleton did not find volcanic rocks on his ascent from the Barrier on his route towards the South Pole.

G. T. Prior, who has described the rocks collected by Scott's expedition, gives the following as belonging to the complex of foundation rocks: gneisses, granites, diorites, banatites, and other eruptive rocks, as well as crystalline limestone, with chondrodite. Professor David and R. Priestley, the geologists of Shackleton's expedition, refer to Ferrar's and Prior's description of the foundation rocks, and state that according to their own investigations the foundation rocks consist of banded gneiss, gneissic granite, grano-diorite, and diorite rich in sphene, besides coarse crystalline limestone as enclosures in the gneiss.

This list of the most important rocks belonging to the foundation series of the parts of South Victoria Land already explored agrees so closely with the rocks from Mount Betty and Scott's Nunatak, that there can be no doubt that the latter also belong to the foundation rocks.

From the exhaustive investigations carried out by Scott's and Shackleton's expeditions it appears that South Victoria Land is a plateau land, consisting of a foundation platform, of great thickness and prominence, above which lie remains, of greater or less extent, of Palæozoic formations, horizontally bedded. From the specimens of rock brought home by Roald Amundsen's expedition it is established that the plateau of foundation rocks is continued eastward to Amundsen's route to the South Pole, and that King Edward VII. Land is probably a northern continuation, on the eastern side of Ross Sea, of the foundation rock plateau of South Victoria Land.

Christiania,

September 26, 1912.

Note by Professor H. Geelmuyden

Christiania,

September 16, 1912.

When requested this summer to receive the astronomical observations from Roald Amundsen's South Pole Expedition, for the purpose of working them out, I at once put myself in communication with Mr. A. Alexander (a mathematical master) to get him to undertake this work, while indicating the manner in which the materials could be best dealt with. As Mr. Alexander had in a very efficient manner participated in the working out of the observations from Nansen's Fram Expedition, and since then had calculated the astronomical observations from Amundsen's Gjöa Expedition, and from Captain Isachsen's expeditions to Spitzbergen, I knew by experience that he was not only a reliable and painstaking calculator, but that he also has so full an insight into the theoretical basis, that he is capable of working without being bound down by instructions.

(Signed) H. Geelmuyden,

Professor of Astronomy,

The Observatory of the University,

Christiania.

Mr. Alexander's Report.

Captain Roald Amundsen,

At your request I shall here give briefly the result of my examination of the observations from your South Pole Expedition. My calculations are based on the longitude for Framheim given to me by Lieutenant Prestrud, 163º 37' W. of Greenwich. He describes this longitude as provisional, but only to such an extent that the final result cannot differ appreciably from it. My own results may also be somewhat modified on a final treatment of the material. But these modifications, again, will only be immaterial, and, in any case, will not affect the result of the investigations given below as to the position of the two Polar stations.

At the first Polar station, on December 15, 1911, eighteen altitudes of the sun were taken in all with each of the expedition's sextants. The latitude calculated from these altitudes is, on an average of both sextants, very near 89º 54', with a mean error of +-2'. The longitude calculated from the altitudes is about 7t (105º) E.; but, as might be expected in this high latitude, the aberrations are very considerable. We may, however, assume with great certainty that this station lies between lat. 89º 52' and 89º 56' S., and between long. 90º and 120º E.

The variation of the compass at the first Polar station was determined by a series of bearings of the sun. This gives us the absolute direction of the last day's line of route. The length of this line was measured as five and a half geographical miles. With the help of this we are able to construct for Polheim a field of the same form and extent as that within which the first Polar station must lie.

At Polheim, during a period of twenty-four hours (December 16 -- 17), observations were taken every hour with one of the sextants. The observations show an upper culmination altitude of 28º 19.2', and a resulting lower culmination altitude of 23º 174'. These combining the above two altitudes, an equal error on the same side in each will have no influence on the result. The combination gives a latitude of 89º 58.6'. That this result must be nearly correct is confirmed by the considerable displacement of the periods of culmination which is indicated by the series of observations, and which in the immediate neighbourhood of the Pole is caused by the change in the sun's declination. On the day of the observations this displacement amounted to thirty minutes in 89º 57', forty-six minutes in 89º 58', and over an hour and a half in 89º 59'. The upper culmination occurred so much too late, and the lower culmination so much too early. The interval between these two periods was thus diminished by double the amount of the displacements given. Now the series of observations shows that the interval between the upper and the lower culmination amounted at the most to eleven hours; the displacement of the periods of culmination was thus at least half an hour. It results that Polheim must lie south of 89º 57', while at the same time we may assume that it cannot lie south of 89º 59'. The moments of culmination could, of course, only be determined very approximately, and in the same way the observations as a whole are unserviceable for the determination of longitude. It may, however, be stated with some certainty that the longitude must be between 30º and 75º E. The latitude, as already mentioned, is between 89º 57' and 89º 59', and the probable position of Polheim may be given roughly as lat. 89º 58.5' S., and long. 60º E.

On the accompanying sketch-chart the letters abcd indicate the field within which the first Polar station must lie; ABCD is the field which is thereby assigned to Polheim; EFGH the field within which Polheim must lie according to the observations taken on the spot itself; P the probable position of Polheim, and L the resulting position of the first Polar station. The position thus assigned to the latter agrees as well as could be expected with the average result of the observations of December 15. According to this, Polheim would be assumed to lie one and a half geographical miles, or barely three kilometres, from the South Pole, and certainly not so much as six kilometres from it.

From your verbal statement I learn that Helmer Hanssen and Bjaaland walked four geographical miles from Polheim in the direction taken to be south on the basis of the observations. On the chart the letters efgh give the field within which the termination of their line of route must lie. It will be seen from this that they passed the South Pole at a distance which, on the one hand, can hardly have been so great as two and a half kilometres, and on the other, hardly so great as two kilometres; that, if the assumed position of Polheim be correct, they passed the actual Pole at a distance of between 400 and 600 metres; and that it is very probable that they passed the actual Pole at a distance of a few hundred metres, perhaps even less.

I am, etc.,

(Signed) Anton Alexander.

Christiania,

September 22, 1912.

Remarks of the Oceanographical Investigation carried out by the "Fram" in the North Atlantic in 1910 and in the South Atlantic in 1911. By Professor Björn Helland-Hansen and Professor Fridtjof Nansen

In the earliest ages of the human race the sea formed an absolute barrier. Men looked out upon its immense surface, now calm and bright, now lashed by storms, and always mysteriously attractive; but they could not grapple with it. Then they learned to make boats; at first small, simple craft, which could only be used when the sea was calm. But by degrees the boats were made larger and more perfect, so that they could venture farther out and weather a storm if it came. In antiquity the peoples of Europe accomplished the navigation of the Mediterranean, and the boldest maritime nation was able to sail round Africa and find the way to India by sea. Then came voyages to the northern waters of Europe, and far back in the Middle Ages enterprising seamen crossed from Norway to Iceland and Greenland and the north-eastern part of North America. They sailed straight across the North Atlantic, and were thus the true discoverers of that ocean.

Even in antiquity the Greek geographers had assumed that the greater part of the globe was covered by sea, but it was not till the beginning of the modern age that any at all accurate idea arose of the extent of the earth's great masses of water. The knowledge of the ocean advanced with more rapid steps than ever before. At first this knowledge only extended to the surface, the comparative area of oceans, their principal currents, and the general distribution of temperature. In the middle of the last century Maury collected all that was known, and drew charts of the currents and winds for the assistance of navigation. This was the beginning of the scientific study of the oceanic waters; at that time the conditions below the surface were still little known. A few investigations, some of them valuable, had been made of the sea fauna, even at great depths, but very little had been done towards investigating the physical conditions. It was seen, however, that there was here a great field for research, and that there were great and important problems to be solved; and then, half a century ago, the great scientific expeditions began, which have brought an entire new world to our knowledge.

It is only forty years since the Challenger sailed on the first great exploration of the oceans. Although during these forty years a quantity of oceanographical observations has been collected with a constant improvement of methods, it is, nevertheless, clear that our knowledge of the ocean is still only in the preliminary stage. The ocean has an area twice as great as that of the dry land, and it occupies a space thirteen times as great as that occupied by the land above sea-level. Apart from the great number of soundings for depth alone, the number of oceanographical stations -- with a series of physical and biological observations at various depths -- is very small in proportion to the vast masses of water; and there are still extensive regions of the ocean of the conditions of which we have only a suspicion, but no certain knowledge. This applies also to the Atlantic Ocean, and especially to the South Atlantic.

Scientific exploration of the ocean has several objects. It seeks to explain the conditions governing a great and important part of our earth, and to discover the laws that control the immense masses of water in the ocean. It aims at acquiring a knowledge of its varied fauna and flora, and of the relations between this infinity of organisms and the medium in which they live. These were the principal problems for the solution of which the voyage of the Challenger and other scientific expeditions were undertaken. Maury's leading object was to explain the conditions that are of practical importance to navigation; his investigations were, in the first instance, applied to utilitarian needs.

But the physical investigation of the ocean has yet another very important bearing. The difference between a sea climate and a continental climate has long been understood; it has long been known that the sea has an equalizing effect on the temperature of the air, so that in countries lying near the sea there is not so great a difference between the heat of summer and the cold of winter as on continents far from the sea-coast. It has also long been understood that the warm currents produce a comparatively mild climate in high latitudes, and that the cold currents coming from the Polar regions produce a low temperature. It has been known for centuries that the northern arm of the Gulf Stream makes Northern Europe as habitable as it is, and that the Polar currents on the shores of Greenland and Labrador prevent any richer development of civilization in these regions. But it is only recently that modern investigation of the ocean has begun to show the intimate interaction between sea and air; an interaction which makes it probable that we shall be able to forecast the main variations in climate from year to year, as soon as we have a sufficiently large material in the shape of soundings.

In order to provide new oceanographical material by modern methods, the plan of the Fram expedition included the making of a number of investigations in the Atlantic Ocean. In June, 1910, the Fram went on a trial cruise in the North Atlantic to the west of the British Isles. Altogether twenty-five stations were taken in this region during June and July before the Fram's final departure from Norway.

The expedition then went direct to the Antarctic and landed the shore party on the Barrier. Neither on this trip nor on the Fram's subsequent voyage to Buenos Aires were any investigations worth mentioning made, as time was too short; but in June, 1911, Captain Nilsen took the Fram on a cruise in the South Atlantic and made in all sixty valuable stations along two lines between South America and Africa.

An exhaustive working out of the very considerable material collected on these voyages has not yet been possible. We shall here only attempt to set forth the most conspicuous results shown by a preliminary examination.

Besides the meteorological observations and the collection of plankton -- in fine silk tow-nets -- the investigations consisted of taking temperatures and samples of water at different depths The temperatures below the surface were ascertained by the best modern reversing thermometers (Richter's); these thermometers are capable of giving the temperature to within a few hundredths of a degree at any depth. Samples of water were taken for the most part with Ekman's reversing water-sampler; it consists of a brass tube, with a valve at each end. When it is lowered the valves are open, so that the water passes freely through the tube. When the apparatus has reached the depth from which a sample is to be taken, a small slipping sinker is sent down along the line. When the sinker strikes the sampler, it displaces a small pin, which holds the brass tube in the position in which the valves remain open. The tube then swings over, and this closes the valves, so that the tube is filled with a hermetically enclosed sample of water. These water samples were put into small bottles, which were afterwards sent to Bergen, where the salinity of each sample was determined. On the first cruise, in June and July, 1910, the observations on board were carried out by Mr. Adolf Schröer, besides the permanent members of the expedition. The observations in the South Atlantic in the following year were for the most part carried out by Lieutenant Gjertsen and Kutschin.

The Atlantic Ocean is traversed by a series of main currents, which are of great importance on account of their powerful influence on the physical conditions of the surrounding regions of sea and atmosphere. By its oceanographical investigations in 1910 and 1911 the Fram expedition has made important contributions to our knowledge of many of these currents. We shall first speak of the investigations in the North Atlantic in 1910, and afterwards of those in the South Atlantic in 1911.

Investigations in the North Atlantic in June and July, 1910.

The waters of the Northern Atlantic Ocean, to the north of lats. 80º and 40º N., are to a great extent in drifting motion north-eastward and eastward from the American to the European side. This drift is what is popularly called the Gulf Stream. To the west of the Bay of Biscay the eastward flow of water divides into two branches, one going south-eastward and southward, which is continued in the Canary Current, and the other going north-eastward and northward outside the British Isles, which sends comparatively warm streams of water both in the direction of Iceland and past the Shetlands and Faroes into the Norwegian Sea and north-eastward along the west coast of Norway. This last arm of the Gulf Stream in the Norwegian Sea has been well explored during the last ten or fifteen years; its course and extent have been charted, and it has been shown to be subject to great variations from year to year, which again appear to be closely connected with variations in the development and habitat of several important species of fish, such as cod, coal-fish, haddock, etc., as well as with variations in the winter climate of Norway, the crops, and other important conditions. By closely following the changes in the Gulf Stream from year to year, it looks as if we should be able to predict a long time in advance any great changes in the cod and haddock fisheries in the North Sea, as well as variations in the winter climate of North-Western Europe.

But the cause or causes of these variations in the Gulf Stream are at present unknown. In order to solve this difficult question we must be acquainted with the conditions in those regions of the Atlantic itself through which this mighty ocean current flows, before it sends its waters into the Norwegian Sea. But here we are met by the difficulty that the investigations that have been made hitherto are extremely inadequate and deficient; indeed, we have no accurate

(Fig. 1. -- Hypothetical Representation of the Surface Currents in the Northern Atlantic in April.

After Nansen, in the Internationale Revue der gesamten Hydrobiologie and Hydrographie, 1912.)

knowledge even of the course and extent of the current in this ocean. A thorough investigation of it with the improved methods of our time is therefore an inevitable necessity.

As the Gulf Stream is of so great importance to Northern Europe in general, but especially to us Norwegians, it was not a mere accident that three separate expeditions left Norway in the same year, 1910 -- Murray and Hjort's expedition in the Michael Sars, Amundsen's trial trip in the Fram, and Nansen's voyage in the gunboat Frithjof -- all with the object of investigating the conditions in the North Atlantic. The fact that on these three voyages observations were made approximately at the same time in different parts of the ocean increases their value in a great degree, since they can thus be directly compared; we are thus able to obtain, for instance, a reliable survey of the distribution of temperature and salinity, and to draw important conclusions as to the extent of the currents and the motion of the masses of water.

Amundsen's trial trip in the Fram and Nansen's voyage in the Frithjof were made with the special object of studying the Gulf Stream in the ocean to the west of the British Isles, and by the help of these investigations it is now possible to chart the current and the extent of the various volumes of water at different depths in this region at that time.

A series of stations taken within the same region during Murray and Hjort's expedition completes the survey, and provides valuable material for comparison.

After sailing from Norway over the North Sea, the Fram passed through the English Channel in June, 1910, and the first station was taken on June 20, to the south of Ireland, in lat. 50º 50' N. and long. 10º 15' W., after which thirteen stations were taken to the westward, to lat. 58º 16' N. and long. 17º 50' W., where the ship was on June 27. Her course then went in a northerly direction to lat. 57º 59' N. and long. 15º 8' W., from which point a section of eleven stations (Nos. 15 -- 25) was made straight across the Gulf Stream to the bank on the north of Scotland, in lat. 59º 88' N. and long. 4º 44' W. The voyage and the stations are represented in Fig. 2. Temperatures and samples of water were taken at all the twenty-four stations at the following depths: surface, 5, 10, 20, 30, 40, 50, 75, 100, 150, 200, 300, 400, and 500 metres (2.7, 5.4, 10.9, 16.3, 21.8, 27.2, 40.8, 54.5, 81.7, 109, 163.5, 218, and 272.5 fathoms) -- or less, where the depth was not so great.

The Fram's southerly section, from Station 1 to 13 (see Fig. 3) is divided into two parts at Station 10, on the Porcupine Bank, south-west of Ireland. The eastern part, between Stations 1 and 10, extends over to the bank south of Ireland, while the three stations of the western part lie in the deep sea west of the Porcupine Bank.

[Fig. 2 and caption: Fig. 2. -- The "Fram's" Route from June 20 to July 7, 1910 (given in an unbroken line -- the figures denote the stations).

The dotted line gives the Frithjof's route, and the squares give five of the Michael Sars's stations.]

In both parts of this section there are, as shown in Fig. 3, two great volumes of water, from the surface down to depths greater than 500 metres, which have salinities between 35.4 and 35.5 per mille. They have also comparatively high temperatures; the isotherm for 10º C. goes down to a depth of about 500 metres in both these parts.

It is obvious that both these comparatively salt and warm volumes of water belong to the Gulf Stream. The more westerly of them, at Stations 11 and 12, and in part 13, in the deep sea to the west of the Porcupine Bank, is probably in motion towards the north-east along the outside of this bank and then into Rockall Channel -- between Rockall Bank and the bank to the west of the

[Fig. 3 and caption: Fig. 3. -- Temperature and Salinity in the "Fram's" Southern Section, June, 1910.]

British Isles -- where a corresponding volume of water, with a somewhat lower salinity, is found again in the section which was taken a few weeks later by the Frithjof from Ireland to the west-north-west across the Rockall Bank. This volume of water has a special interest for us, since, as will be mentioned later, it forms the main part of that arm of the Gulf Stream which enters the Norwegian Sea, but which is gradually cooled on its way and mixed with fresher water, so that its salinity is constantly decreasing. This fresher water is evidently derived in great measure directly from precipitation, which is here in excess of the evaporation from the surface of the sea.

The volume of Gulf Stream water that is seen in the eastern part (east of Station 10) of the southern Fram section, can only flow north-eastward to a much less extent, as the Porcupine Bank is connected with the bank to the west of Ireland by a submarine ridge (with depths up to about 300 metres), which forms a great obstacle to such a movement.

The two volumes of Gulf Stream water in the Fram's southern section of 1910 are divided by a volume of water, which lies over the Porcupine Bank, and has a lower salinity and also a somewhat lower average temperature. On the bank to the south of Ireland (Stations 1 and 2) the salinity and average temperature are also comparatively low. The fact that the water on the banks off the coast has lower salinities, and in part lower temperatures, than the water outside in the deep sea, has usually been explained by its being mixed with the coast water, which is diluted with river water from the land. This explanation may be correct in a great measure; but, of course, it will not apply to the water over banks that lie out in the sea, far from any land. It appears, nevertheless, on the Porcupine Bank, for instance, and, as we shall see later, on the Rockall Bank, that the water on these ocean banks is -- in any case in early summer -- colder and less salt than the surrounding water of the sea. It appears from the Frithjof section across the Rockall Bank, as well as from the two Fram sections, that this must be due to precipitation combined with the vertical currents near the surface, which are produced by the cooling of the surface of the sea in the course of the winter. For, as the surface water cools, it becomes heavier than the water immediately below, and must then sink, while it is replaced by water from below. These vertical currents extend deeper and deeper as the cooling proceeds in the course of the winter, and bring about an almost equal temperature and salinity in the upper waters of the sea during the winter, as far down as this vertical circulation reaches. But as the precipitation in these regions is constantly decreasing the salinity of the surface water, this vertical circulation must bring about a diminution of salinity in the underlying waters, with which the sinking surface water is mixed into a homogeneous volume of water. The Frithjof section in particular seems to show that the vertical circulation in these regions reaches to a depth of 500 or 600 metres at the close of the winter. If we consider, then, what must happen over a bank in the ocean, where the depth is less than this, it is obvious that the vertical circulation will here be prevented by the bottom from reaching the depth it otherwise would, and there will be a smaller volume of water to take part in this circulation and to be mixed with the cooled and diluted surface water. But as the cooling of the surface and the precipitation are the same there as in the surrounding regions, the consequence must be that the whole of this volume of water over the bank will be colder and less salt than the surrounding waters. And as this bank water, on account of its lower temperature, is heavier than the water of the surrounding sea, it will have a tendency to spread itself outwards along the bottom, and to sink down along the slopes from the sides of the bank. This obviously contributes to increase the opposition that such banks offer to the advance of ocean currents, even when they lie fairly deep.

These conditions, which in many respects are of great importance, are clearly shown in the two Fram sections and the Frithjof section.

The Northern Fram section went from a point to the north-west of the Rockall Bank (Station 15), across the northern end of this bank (Station 16), and across the northern part of the wide channel (Rockall Channel) between it and Scotland. As might be expected, both temperature and salinity are lower in this section than in the southern one, since in the course of their slow northward movement the waters are cooled, especially by the vertical circulation in winter already mentioned, and are mixed with water containing less salt, especially precipitated water. While in the southern section the isotherm for 10º C. went down to 500 metres, it here lies at a depth of between 50 and 25 metres. In the comparatively short distance between the two sections, the whole volume of water has been cooled between 1º and 2º C. This represents a great quantity of warmth, and it is chiefly given off to the air, which is thus warmed over a great area. Water contains more than 3,000 times as much warmth as the same volume of air at the same temperature. For example, if 1 cubic metre of water is cooled 1º, and the whole quantity of warmth thus taken from the water is given

[Fig. 4. -- Temperature and Salinity in the "Fram's" Northern Section, July 1910]

to the air, it is sufficient to warm more than 3,000 cubic metres of air 1º, when subjected to the pressure of one atmosphere. In other words, if the surface water of a region of the sea is cooled 1º to a depth of 1 metre, the quantity of warmth thus taken from the sea is sufficient to warm the air of the same region 1º up to a height of much more than 3,000 metres, since at high altitudes the air is subjected to less pressure, and consequently a cubic metre there contains less air than at the sea-level. But it is not a depth of 1 metre of the Gulf Stream that has been cooled 1º between these two sections; it is a depth of about 500 metres or more, and it has been cooled between 1º and 2º C. It will thus be easily understood that this loss of warmth from the Gulf Stream must have a profound influence on the temperature of the air over a wide area; we see how it comes about that warm currents like this are capable of rendering the climate of countries so much milder, as is the case in Europe; and we see further how comparatively slight variations in the temperature of the current from year to year must bring about considerable variations in the climate; and how we must be in a position to predict these latter changes when the temperature of the currents becomes the object of extensive and continuous investigation. It may be hoped that this is enough to show that far-reaching problems are here in question.

The salinity of the Gulf Stream water decreases considerably between the Fram's southern and northern sections. While in the former it was in great part between 35.4 and 35.5 per mille, in the latter it is throughout not much more than 35.3 per mille. In this section, also, the waters of the Gulf Stream are divided by an accumulation of less salt and somewhat colder bank water, which here lies over the Rockall Bank (Station 16). On the west side of this bank there is again (Station 15) salter and warmer Gulf Stream water, though not quite so warm as on the east. From the Frithjof section, a little farther south, it appears that this western volume of Gulf Stream water is comparatively small. The investigations of the Fram and the Frithjof show that the part of the Gulf Stream which penetrates into the Norwegian Sea comes in the main through the Rockall Channel, between the Rockall Bank and the bank to the west of the British Isles; its width in this region is thus considerably less than was usually supposed. Evidently this is largely due to the influence of the earth's rotation, whereby currents in the northern hemisphere are deflected to the right, to a greater degree the farther north they run. In this way the ocean currents, especially in northern latitudes, are forced against banks and coasts lying to the right of them, and frequently follow the edges, where the coast banks slope down to the deep. The conclusion given above, that the Gulf Stream comes through the Rockall Channel, is of importance to future investigations; it shows that an annual investigation of the water of this channel would certainly contribute in a valuable way to the understanding of the variations of the climate of Western Europe.

We shall not dwell at greater length here on the results of the Fram's oceanographical investigations in 1910. Only when the observations then collected, as well as those of the Frithjof's and Michael Sars's voyages, have been fully worked out shall we be able to make a complete survey of what has been accomplished.

Investigations in the South Atlantic, June to August, 1911.

In the South Atlantic we have the southward Brazil Current on the American side, and the northward Benguela Current on the African side. In the southern part of the ocean there is a wide current flowing from west to east in the west wind belt. And in its northern part, immediately south of the Equator, the South Equatorial Current flows from east to west. We have thus in the South Atlantic a vast circle of currents, with a motion contrary to that of the hands of a clock. The Fram expedition has now made two full sections across the central part of the South Atlantic; these sections take in both the Brazil Current and the Benguela Current, and they lie between the eastward current on the south and the westward current on the north. This is the first time that such complete sections have been obtained between South America and Africa in this part of the ocean. And no doubt a larger number of stations were taken on the Fram's voyage than have been taken -- with the same amount of detail -- in the whole South Atlantic by all previous expeditions put together.

When the Fram left Buenos Aires in June, 1911, the expedition went eastward through the Brazil Current. The first station was taken in lat. 36º 18' S. and long. 43º 15' W.; this was on June 17. Her course was then north-east or east until Station 32 in lat. 20º 30' S. and long. 8º 10' E.; this station lay in the Benguela Current, about 800 miles from the coast of Africa, and it was taken on July 22. From there she went in a gentle curve

[Fig. 5 and caption]

past St. Helena and Trinidad back to America. The last station (No. 60) was taken on August 19 in the Brazil Current in lat. 24º 39' S. and about long. 40º W.; this station lay about 200 miles south-east of Rio de Janeiro.

There was an average distance of 100 nautical miles between one station and the next. At nearly all the stations investigations were made at the following depths: surface, 5, 10, 25, 50, 100, 150, 200, 250, 300, 400, 500, 750, and 1,000 metres (2.7, 5.4, 13.6, 27.2, 54.5, 81.7, 109, 136.2, 163.5, 218, 272.5, and 545 fathoms). At one or two of the stations observations were also taken at 1,500 and 2,000 metres (817.5 and 1,090 fathoms).

The investigations were thus carried out from about the middle of July to the middle of August, in that part of the southern winter which corresponds to the period between the middle of

[Fig. 6]

Fig. 6. -- Currents in the South Atlantic (June -- August, 1911).

December and the middle of February in the northern hemisphere We must first see what the conditions were on the surface in those regions in the middle of the winter of 1911.

It must be remembered that the currents on the two sides of the ocean flow in opposite directions. Along the coast of Africa, we have the Benguela Current, flowing from south to north; on the American side the Brazil Current flows from the tropics southward. The former current is therefore comparatively cold and the latter comparatively warm. This is clearly seen on the chart, which shows the distribution of temperatures and salinities on the surface. In lat. 20º S. it was only about 17º C. off the African coast, while it was about 23º C. off the coast of Brazil.

The salinity depends on the relation between evaporation and the addition of fresh water. The Benguela Current comes from

[Fig. 7]

Fig. 7. -- Salinities and Temperatures at the Surface in the South Atlantic (June -- August, 1911) regions where the salinity is comparatively low; this is due to the acquisition of fresh water in the Antarctic Ocean, where the evaporation from the surface is small and the precipitation comparatively large. A part of this fresh water is also acquired by the sea in the form of icebergs from the Antarctic Continent. These icebergs melt as they drift about the sea.

Immediately off the African coast there is a belt where the salinity is under 35 per mille on the surface; farther out in the Benguela Current the salinity is for the most part between 35 and 36 per mille. As the water is carried northward by the current, evaporation becomes greater and greater; the air becomes comparatively warm and dry. Thereby the salinity is raised. The Benguela Current is then continued westward in the South Equatorial Current; a part of this afterwards turns to the north-west, and crosses the Equator into the North Atlantic, where it joins the North Equatorial Current. This part must thus pass through the belt of calms in the tropics. In this region falls of rain occur, heavy enough to decrease the surface salinity again. But the other part of the South Equatorial Current turns southward along the coast of Brazil, and is then given the name of the Brazil Current. The volume of water that passes this way receives at first only small additions of precipitation; the air is so dry and warm in this region that the salinity on the surface rises to over 37 per mille. This will be clearly seen on the chart; the saltest water in the whole South Atlantic is found in the northern part of the Brazil Current. Farther to the south in this current the salinity decreases again, as the water is there mixed with fresher water from the South. The River La Plata sends out enormous quantities of fresh water into the ocean. Most of this goes northward, on account of the earth's rotation; the effect of this is, of course, to deflect the currents of the southern hemisphere to the left, and those of the northern hemisphere to the right. Besides the water from the River La Plata, there is a current flowing northward along the coast of Patagonia -- namely, the Falkland Current. Like the Benguela Current, it brings water with lower salinities than those of the waters farther north; therefore, in proportion as the salt water of the Brazil Current is mixed with the water from the River La Plata and the Falkland Current, its salinity decreases. These various conditions give the explanation of the distribution of salinity and temperature that is seen in the chart.

Between the two long lines of section there is a distance of between ten and fifteen degrees of latitude. There is, therefore, a considerable difference in temperature. In the southern section the average surface temperature at Stations 1 to 26 (June 17 to July 17) was 17.9º C.; in the northern section at Stations 36 to 60 (July 26 to August 19) it was 21.6º C. There was thus a difference of 3.7º C. If all the stations had been taken simultaneously, the difference would have been somewhat greater; the northern section was, of course, taken later in the winter, and the temperatures were therefore proportionally lower than in the southern section. The difference corresponds fairly accurately with that which Kr:ummel has calculated from previous observations.

We must now look at the conditions below the surface in that part of the South Atlantic which was investigated by the Fram Expedition.

The observations show in the first place that both temperatures and salinities at every one of the stations give the same values from the surface downward to somewhere between 75 and 150 metres (40.8 and 81.7 fathoms). This equalization of temperature and salinity is due to the vertical currents produced by cooling in winter; we shall return to it later. But below these depths the temperatures and salinities decrease rather rapidly for some distance.

The conditions of temperature at 400 metres (218 fathoms) below the surface are shown in the next little chart. This chart is based on the Fram Expedition, and, as regards the other parts of the ocean, on Schott's comparison of the results of previous expeditions. It will be seen that the Fram's observations agree very well with previous soundings, but are much more detailed.

The chart shows clearly that it is much warmer at 400 metres (218 fathoms) in the central part of the South Atlantic than either farther north -- nearer the Equator -- or farther south. On the Equator there is a fairly large area where the temperature is only 7º or 8º C. at 400 metres, whereas in lats. 2Oº to 30º S. there are large regions where it is above 12º C.; sometimes above 13º C., or even 14ºC. South of lat. 30º S. the temperature decreases again rapidly; in the chart no lines are drawn for temperatures below 8º C., as we have not sufficient observations to show the course of these lines properly. But we know that the temperature at 400 metres sinks to about 0º C. in the Antarctic Ocean.

[Fig. 8]

Fig. 8. -- Temperatures (Centigrade) at a Depth of 400 Metres (218 Fathoms).

At these depths, then, we find the warmest water within the region investigated by the Fram. If we now compare the distribution of temperature at 400 metres with the chart of currents in the South Atlantic, we see that the warm region lies in the centre of the great circulation of which mention was made above. We see that there are high temperatures on the left-hand side of the currents, and low on the right-hand side. This, again, is an effect of the earth's rotation, for the high temperatures mean as a rule that the water is comparatively light, and the low that it is comparatively heavy. Now, the effect of the earth's rotation in the southern hemisphere is that the light (warm) water from above is forced somewhat down on the left-hand side of the current, and that the heavy (cold) water from below is raised somewhat. In the northern hemisphere the contrary is the case. This explains the cold water at a depth of 400 metres on the Equator; it also explains the fact that the water immediately off the coasts of Africa and South America is considerably colder than farther out in the ocean. We now have data for studying the relation between the currents and the distribution of warmth in the volumes of water in a way which affords valuable information as to the movements themselves. The material collected by the Fram will doubtless be of considerable importance in this way when it has been finally worked out.

Below 400 metres (218 fathoms) the temperature further decreases everywhere in the South Atlantic, at first rapidly to a depth between 500 and 1,000 metres (272.5 and 545 fathoms), afterwards very slowly. It is possible, however, that at the greatest depths it rises a little again, but this will only be a question of hundredths, or, in any case, very few tenths of a degree.

It is known from previous investigations in the South Atlantic, that the waters at the greatest depths, several thousand metres below the surface, have a temperature of between 0º and 3º C. Along the whole Atlantic, from the extreme north (near Iceland) to the extreme south, there runs a ridge about half-way between Europe and Africa on the one side, and the two American continents on the other. A little to the north of the Equator there is a slight elevation across the ocean floor between South America and Africa. Farther south (between lats. 25º and 35º S.) another irregular ridge runs across between these continents. We therefore have four deep regions in the South Atlantic, two on the west (the Brazilian Deep and the Argentine Deep) and two on the east (the West African Deep and the South African Deep). Now it has been found that the "bottom water" in these great deeps -- the bottom lies more than 5,000 metres (2,725 fathoms) below the surface -- is not always the same. In the two western deeps, off South America, the temperature is only a little above 0º C. We find about the same temperatures in the South African Deep, and farther eastward in a belt that is continued round the whole earth. To the south, between this belt and Antarctica, the temperature of the great deeps is much lower, below 0º C. But in the West African Deep the temperature is about 2º C. higher; we find there the same temperatures of between 2º and 2.5º C. as are found everywhere in the deepest parts of the North Atlantic. The explanation of this must be that the bottom water in the western part of the South Atlantic comes from the south, while in the north-eastern part it comes from the north. This is connected with the earth's rotation, which has a tendency to deflect currents to the left in the southern hemisphere. The bottom water coming from the south goes to the left -- that is, to the South American side; that which comes from the north also goes to the left -- that is, to the African side.

The salinity also decreases from the surface downward to 600 to 800 metres (about 300 to 400 fathoms), where it is only a little over 34 per mille, but under 34.5 per mille; lower down it rises to about 34.7 per mille in the bottom water that comes from the south, and to about 34.9 per mille in that which comes from the North Atlantic.

We mentioned that the Benguela Current is colder and less salt at the surface than the Brazil Current. The same thing is found in those parts of the currents that lie below the surface. This is clearly shown in Fig. 9, which gives the distribution of temperature at Station 32 in the Benguela Current, and at Station 60 in the Brazil Current; at the various depths down to 500 metres (272.5 fathoms) it was between 5º and 7º C. colder in the former than in the latter. Deeper down the difference becomes less, and at 1,000 metres (545 fathoms) there was only a difference of one or two tenths of a degree.

Fig. 10 shows a corresponding difference in salinities; in the first 200 metres below the surface the water was about

[Fig. 9.]

Fig. 9. -- Temperatures at Station 32 (In the Benguela Current, July 22, 1911), and at Station 6O (In the Brazil Current, August 19, 1911).

1 per mille more saline in the Brazil Current than in the Benguela Current. Both these currents are confined to the upper waters; the former probably goes down to a depth of about 1,000 metres (545 fathoms), while the latter does not reach a depth of much more than 500 metres. Below the two currents the conditions are fairly homogeneous, and there is no difference worth mentioning in the salinities.

The conditions between the surface and a depth of 1,000 metres along the two main lines of course are clearly shown in the two sections (Figs. 11 and l2). In these the isotherms for every second degree are drawn in broken lines. Lines connecting points with the same salinity (isohalins) are drawn unbroken, and, in addition, salinities above 35 per mille are shown by shading. Above is a series of figures, giving the numbers of the stations. To understand

[Fig. 10 and caption]

the sections rightly it must be borne in mind that the vertical scale is 2,000 times greater than the horizontal.

Many of the conditions we have already mentioned are clearly apparent in the sections: the small variations between the surface and a depth of about 100 metres at each station; the decrease of temperature and salinity as the depth increases; the high values both of temperature and salinity in the western part as compared with the eastern. We see from the sections how nearly the isotherms and isohalins follow each other. Thus, where the temperature is 12º C., the water almost invariably has a salinity very near 35 per mille. This water at 12º C., with a salinity of 35 per mille, is found in the western part of the area (in the Brazil Current) at a depth of 500 to 600 metres, but in the eastern part (in the Benguela Current) no deeper than 200 to 250 metres (109 to 136 fathoms).

We see further in both sections, and especially in the southern one, that the isotherms and isohalins often have an undulating course, since the conditions at one station may be different from those at the neighbouring stations. To point to one or two examples: at Station 19 the water a few hundred metres down was comparatively warm; it was, for instance, 12º C. at about 470 metres (256 fathoms) at this station; while the same temperature was found at about 340 metres (185 fathoms) at both the neighbouring stations, 18 and 20. At Station 2 it was relatively cold, as cold as it was a few hundred metres deeper down at Stations 1 and 3.

These undulating curves of the isotherms and isohalins are familiar to us in the Norwegian Sea, where they have been shown in most sections taken in recent years. They may be explained in more than one way. They may be due to actual waves, which are transmitted through the central waters of the sea. Many things go to show that such waves may actually occur far below the surface, in which case they must attain great dimensions; they must, indeed, be more than 100 metres high at times, and yet -- fortunately -- they are not felt on the surface. In the Norwegian Sea we have frequently found these wave-like rises and falls. Or the curves may be due to differences in the rapidity and direction of the currents. Here the earth's rotation comes into play, since, as mentioned above, it causes zones of water to be depressed on one side and raised on the other; and the degree of force with which this takes place is dependent on the rapidity of the current and on the geographical latitude. The effect is slight in the tropics, but great in high latitudes. This, so far as it goes, agrees with the