66

he himself moved, on Aug. 5, the day after war had begun, the first vote of credit for £100,000,000, maintaining that the war has been forced upon us." The fight was, first, to fulfil a solemn international obligation; secondly, to vindicate the principle that small nationalities were not to be crushed, in defiance of international good faith, by the arbitrary will of a strong and overmastering power. No nation, he said, ever entered into a great struggle with a clearer conscience and a stronger conviction that it was fighting for principles vital to the civilized world.

In response to a public demand, peremptorily voiced in the press, he now brought Lord Kitchener, who was on the point of starting back, after a brief visit home, to resume his duties as British agent in Egypt, into the Cabinet as Minister of War, surrendering to him the seals which he had held himself for over four months, and he gave him a wide discretion in conducting the war by land. The conduct of the war remained ultimately with the Cabinet, but its day-to-day direction was practically carried on by Mr. Asquith, Lord Kitchener, and Mr. Churchill, with the assistance of their technical advisers. As Prime Minister, too, Mr. Asquith must be accorded his full share in the important measures taken by the Cabinet at this time, such as the financial moratorium, the prompt despatch of the expeditionary force, the enrolment of Kitchener's army, the glad acceptance of colonial help, the decision to bring over native troops from India, and the Defence of the Realm Act. He, however, strained his relations with the Unionists by determining to pass the Home Rule and Welsh Disestablishment bills under the Parliament Act, only providing that neither should come into effect till after the war, and that special provision should be made for Ulster, which should in no circumstances be coerced. He undertook a series of speeches in the autumn, notable alike for patriotic vigour and for lofty eloquence, in order to educate the nation as regards the objects and necessity of the war, and to stimulate recruiting. At the Guildhall on Sept. 4 he said that this was not merely a material but a spiritual conflict, and recalled how England had in the Napoleonic Wars responded to Pitt's dying appeal to her to save Europe by her example. At Edinburgh, on Sept. 18, he said that the German creed of material force was a purblind philosophy, and that, while the British task might take months or years, the economic, monetary, and military and naval position was encouraging. At Dublin, on Sept. 25, he appealed to Ireland to take her due share in a war which was being fought in the interests of small nations. At Cardiff, on Oct. 2, he revealed the fact that, in 1912, the Cabinet had formally notified the German Government that Great Britain would neither make nor join in any unprovoked attack on Germany," but that Germany had demanded in response a British pledge of absolute neutrality if she were engaged in war-a pledge which, of course, Britain could not possibly give. He finished up this series of orations by a resolute speech at Guildhall on Lord Mayor's day; when he told the city that it would be a long-drawnout struggle, but that England would not sheathe the sword until Belgium had recovered all and more than all that she had sacrificed, until France was adequately secured against the menace of aggression, until the rights of the smaller nationalities were placed on an unassailable foundation, until the military dominion of Prussia was fully and finally destroyed. On Nov. 25 he formed a war council, consisting of the Chancellor of the Exchequer, the Foreign Secretary, the Indian Secretary and Lord Haldane, in addition to Lord Kitchener, Mr. Churchill, and himself; but the main responsibility still rested on the last three, and the naval and military experts attended in a somewhat undefined position.

how to prevent the occurrence during war of industrial disputes, which frequently broke out in the first half of 1915. Drink and strikes had a close bearing on the problem which became specially urgent in April, the absolute necessity of an enormous increase in munitions of war. The Times revealed the perilous shortage at the front; Mr. Lloyd George dilated upon it in the House; but Mr. Asquith, in a speech at Newcastle-on-Tyne on April 30, which was mainly devoted to emphasizing the importance of matériel in this war and to encouraging miners, shipbuilders, engineers, iron workers, and dockers to further efforts, raised a storm of criticism by denying that the operations in the field had been crippled because of a want of ammunition.

The uneasiness in the country immediately increased, and there was a pronounced demand for broadening the basis of Government. On May 12 Mr. Asquith repudiated the idea that any such step was in contemplation; but a week later, the quarrel which had developed between Mr. Churchill and Lord Fisher at the Admiralty convinced him that there must be a change, and he invited the Unionists, the Labour party, and the leaders of the two Irish parties to join him in office, by forming a Coalition Ministry. From all whom he invited, but Mr. Redmond, he received acceptances, and he was able to find places in his new Cabinet for them without excluding any important previous colleague of his own, except Lord Haldane, whose German affinities had offended public opinion. He gained the services of many powerful men among the Unionists-Mr. Bonar Law, Lord Lansdowne, Mr. Balfour, Lord Curzon, Mr. Chamberlain, Mr. Long, Mr. F. E. Smith, Lord Robert Cecil, Lord Selborne; of Mr. Henderson and Mr. Brace from the Labour party; and of Sir Edward Carson, the Ulster leader. But he kept the premiership in his own hands, and retained Sir Edward Grey at the Foreign Office, and Lord Kitchener at the War Office. He explained his decision in the House of Commons in these words:

What I came to think was needed, was such a broadening of the basis of the Government as would take away from it even the semblance of a one-sided or party character, and would demonstrate beyond the possibility of doubt, not only to our own people but to the whole world, that after nearly a year of war, with all its fluctuations and vicissitudes, the British people were more resolute than ever, with one heart and one purpose, to obliterate all distinctions and unite every personal and political as well as every moral and material force in the prosecution of their cause.

He emphasized the facts (1) that in the Coalition no surrender was implied of convictions on either side; (2) that there was no change in national policy, which was " to pursue this war at any cost to a victorious issue." His Coalition Government made a good start. He constituted a new Ministry of Munitions, presided over by Mr. Lloyd George, who had by this time impressed the public as being the most resolute and determined of his colleagues; he and his Cabinet issued a great war loan; they introduced a measure for national registration; they imposed an enormously increased taxation; and there was established in the Cabinet a system of pooling salaries, so that every minister should receive the same amount. In June Mr. Asquith paid a four days' visit to the British front in France; and in July he attended a conference at Calais in which British statesmen and generals met French statesmen and generals in order to coördi nate Allied action-the first of many conferences of the kind. On the adjournment of Parliament on July 28 he said that the war had become a struggle of endurance.

As the fervour of the early months of the war died away, many troublesome questions embarrassed Mr. Asquith and his Government. Besides the anxious problem of the Dardanelles expedition, he had to consider whether the system of compulsory service, hateful to the traditions of the Liberal party, had not become inevitable; how to eradicate spying, and to what extent to intern aliens; how to deal with the problem of the liquor trade

was the third loss of a colleague which the Prime Minister had suffered since the Coalition. Sir Edward Carson, the AttorneyGeneral, had resigned in the autumn owing to the muddles of ministerial policy in the Balkans, and Mr. Churchill because of his exclusion from the immediate direction of the war. All three became occasionally keen critics of their former colleagues, whose delays in this vital matter of universal service weakened and discredited them in the country.

Mr. Asquith took a further step early in 1916 in the direction of close coöperation between the Allies by attending, along with Sir E. Grey, Mr. Lloyd George, Lord Kitchener and Gen. Sir William Robertson, an Allied conference in Paris, representative not only of England and France, but of Russia, Italy, Japan, Belgium, Serbia, and Portugal. Thence he went on to Rome, where he visited the Pope, and made a speech in the Capitol declaring the solidarity of Italy, France, and England at that critical moment of the world's history; afterwards proceeding to the Italian headquarters, where he was received by King Victor Emanuel and Gen. Cadorna. Later, in June, he and his Government arranged an economic conference, also in Paris, which provided for measures of economic union between the Allies, for conservation of the national resources of Allied countries, and for economic protection against enemy trade "penetration " and" dumping" after the war. His special attention was claimed at the end of April by rebellion in Ireland, the most serious incident of which was the capture of a great part of Dublin for a week by rebels (see IRELAND). After the suppression of the rising by the troops and the prompt execution of the leaders, he appointed a commission of inquiry, and he himself visited Ireland and returned with a conviction that a united effort must be made to reconstitute Irish government. He appointed Mr. Lloyd George to negotiate and formulate suggestions. In the result he proposed a provisional settlement, for the war and 12 months after, on the basis of bringing the Home Rule Act with certain amendments into immediate operation, with the exclusion of six Ulster counties. To this Sir Edward Carson agreed, but Mr. Redmond objected to the amendments, and nothing was done. The negotiations lost Mr. Asquith the services of Lord Selborne as the rebellion had deprived him of those of Mr. Birrell, the Chief Secretary for Ireland.

The basis of his ministry was rudely shaken in the summer of 1916 by the loss of Lord Kitchener at sea. Lord Kitchener's place at the War Office was taken by Mr. Lloyd George, whose reputation for "getting things done" had been enormously enhanced by the energy with which he had organized the Ministry of Munitions. The attack on the Somme seemed to promise an end to the trench war, but after many weeks of most determined fighting the German line was not broken through; and in the latter part of the year Rumania was crushed. These events increased public dissatisfaction, which had been stimulated by half-hearted dealings with the blockade of Germany, with the food problem, and with the creation of an adequate aerial force; and public criticism was focused on Mr. Asquith, whose incautious phrase of six years before-" wait and see -was frequently flung in his face. In the House of Commons two strong committees, one of Liberals and one of Conservatives, had been formed for the purpose of the resolute prosecution of the war and the keeping of ministers up to the mark. Mr. Asquith's speeches were always resolute enough; he promptly denounced any overtures of pacifists for a premature peace; but he was thought to be lacking in initiative, and to carry into the counsels of war somewhat the attitude of an impartial Cabinet chairman weighing pros and cons and counting heads for a decision.

The War Council initiated under his Liberal Government was continued with very little modification, save in personnel, under the Coalition; and the final authority remained with the Cabinet. It was felt that a small body, sitting daily, with power to act at once without reference, was essential for the proper conduct of the war. Mr. Lloyd George, the most active member of the War Council, by a letter on Dec. 1, demanded the establishment of such a body, with himself as one of its members, but

giving Mr. Asquith a consultative membership and a power of veto. But it was clear that the effect must be to transfer the main conduct of the war from Mr. Asquith to Mr. Lloyd George. Mr. Asquith, who had consented to reconstruct his Government, refused Mr. Lloyd George's ultimatum; and on Dec. 5 Mr. Lloyd George resigned. Without him Mr. Asquith clearly could not carry on, and he himself resigned the same evening, being succeeded, after some complications, by Mr. Lloyd George. So ended a premiership which had lasted nearly nine years, and left an ineffaceable mark on English history. He carried into retirement his principal Liberal colleagues, including Lord Grey of Fallodon; and many tributes of regard and respect were paid him by the Unionists who had been his colleagues.

After his resignation Mr. Asquith took his seat on the front Opposition bench; but he disclaimed being in any sense a leader of Opposition, and affirmed that his one desire was to give the Government the benefit of whatever experience he had gained. He maintained this attitude throughout 1917, making resolute and helpful speeches in different parts of the country on behalf of the national war aims. In Parliament he rendered material assistance to the Ministerial Franchise bill; and he announced that the services of women during the war had converted him to female suffrage. In 1918 he became rather more critical, and in particular called parliamentary attention to a letter in which Gen. Sir Frederick Maurice, formerly Director of Military Operations, challenged the veracity of ministerial statements. He moved to refer the general's charges to a select committee of the House, but was beaten on a division by 293 votes to 106. This action, taken during the period of the alarming German advance, marked a definite cleavage with the Government, which was widened after the Armistice by the conditions under which the general election was held in December. Mr. Asquith and those of his colleagues who had not joined Mr. Lloyd George, together with a considerable section of Liberal members, declined to pledge their support to the Coalition Government, and desired to be returned as independent Liberals. As the electorate was resolved that those who had won the war should make the peace and begin the reconstruction of the country, he and the whole of his principal colleagues lost their seats, and only 28 of his followers in all were returned. He did not come back to Parliament till Feb. 1920, when he was elected at a by-election for Paisley. This time he appeared as the leader of the independent Liberal Opposition which had been temporarily led in his absence by Sir Donald Maclean; but his followers, though they had gained some seats since the general election, were still smaller in number in Parliament than the representatives of Labour. Possibly for that reason he was more active in the country than in Parliament, devoting himself to efforts for reviving the Liberal party. He maintained that the time was come to put an end to the Coalition and resume party Government. He attacked ministers for their departures from Free Trade, for their wasteful administration, and for their policy in Ireland. He strongly condemned reprisals in that island, and declared for Dominion Home Rule. For a time he seemed to be

recovering his hold on the country; but in the last half of 1920 and in 1921 there was a setback. It was no help to his political position that Mrs. Asquith published in the autumn of 1920 a volume of very frank and indiscreet Reminiscences.

In 1918 Mr. Asquith himself published a volume of Occasional Addresses, delivered between the years 1893-1916, thus reminding the world that he was a worthy successor of a long line of scholarly and intellectual Prime Ministers, capable of treating with distinction and acceptance matters of the mind wholly unconnected with politics. The book contained, amongst others, Rectorial Addresses to the universities of Glasgow and Aberdeen, a Presidential Address to the Classical Association, and a dissertation on "biography" read before the Edinburgh Philosophical Institution. The universities of the country duly recognized the claims made upon them by his scholarship. Besides being elected to the rectorships, first of Glasgow and then of Aberdeen, he received honorary degrees from Oxford, Cambridge,

Mr. Asquith had four sons and a daughter by his first marriage, and a son and a daughter by his second marriage. His eldest son, RAYMOND ASQUITH (1878-1916), had a brilliant career at Oxford, where he was a scholar of Balliol, gained a first class both in classical moderations and in lit. hum., won the Ireland, Craven, and Derby scholarships, was president of the Union, and was finally elected in 1902 to a fellowship at All Souls. He went to the bar, and acquired a considerable practice, but when the World War broke out he at once sought a commission and was killed in action in France as a lieutenant in the Grenadier Guards. He left a widow and three children. The third son, ARTHUR MELLAND ASQUITH (1883- ), distinguished himself greatly in the war, becoming brigadier-general and D.S.O. In 1918 he was appointed controller of the Trench Warfare Department of the Ministry of Munitions, and in 1919 controller, Appointments Department, and member of council at the Ministry of Labour. The fourth son, CYRIL ASQUITH (1890- ), followed his brother Raymond in his Oxford career. He was a scholar of Balliol, gained a first class both in classical moderations and in lit. hum., won the Hertford, Ireland, Craven, and Eldon scholarships, and was elected fellow of Magdalen. The war came just at the close of his undergraduate life, and he served in the army before being called to the bar in 1920. Mr. Asquith's daughter by his first wife, VIOLET, married his private secretary, Sir Maurice Bonham-Carter; his daughter by his second wife, ELIZABETH, married Prince Antoine Bibesco, for 16 years a member of the Rumanian Legation in London, and in 1921 appointed Rumanian minister to the United States. (G. E. B.)

ASTOR, WILLIAM WALDORF ASTOR, IST VISCOUNT (18481919) [see 2.794], died at Brighton Oct. 18 1919. He was in 1916 raised to the peerage, and in 1917 was created a viscount.

His son, WILLIAM WALDORF ASTOR, 2ND VISCOUNT Astor, born in New York May 19 1879, was educated at Eton and New College, Oxford. In 1911 he successfully contested the Sutton division of Plymouth as a Unionist, but vacated his seat in 1919 on succeeding to his father's peerage. He was chairman of the Government Committee on tuberculosis and of the State Medical Research Committee. During the World War he was inspector of quartermaster-general services, and in 1918 became parliamentary secretary to the Prime Minister. In Jan. 1919 he was appointed parliamentary secretary to the Local Government Board, and retained the same position on the formation of the Ministry of Health in Aug. 1919. His wife, NANCY WITCHER ASTOR, born in Virginia May 19 1879, was the daughter of Chiswell Dabney Langhorne, of an old Virginian family. She married in 1897 Robert Gould Shaw, of Boston, from whom she obtained a divorce in 1903, and in 1906 married William Waldorf Astor, Jr. When her husband succeeded to the viscountcy, Lady Astor, who had taken much interest in the local affairs of her husband's former constituency in Plymouth, was adopted there as Coalition Unionist candidate for the vacant seat in Parliament. She was elected by a substantial majority Nov. 28 1919, thus becoming the first woman to sit in the House of Commons.

ASTRONOMY (see 2.800).-This article is intended to cover the principal advances made during 1910-21 in all the departments of astronomy (including astrophysics) with the exception of the more technical results of celestial spectroscopy. Those investigations have been selected for discussion which appear to have had most conspicuous influence on the general current of ideas.

, I. OBSERVATIONAL ASTRONOMY

The Sun (see 26.85).-By means of the spectroheliograph it is possible to obtain photographs of the sun in light of a single wave-length; we thus obtain a picture of the distribution of the matter which emits this wave-length, or a negative of the matter which absorbs it. In practice either calcium or hydrogen light is used, since these elements furnish spectral lines sufficiently isolated to give good results. The emission of a particular line depends on favourable conditions of temperature and density, and these will vary with the level in the sun's atmosphere. Thus the function of the spectroheliograph is not so much to separate the distributions of particular elements as to isolate different levels in the sun's atmosphere, and provide separate photographs of what is occurring at each level.

The recent pictures obtained with this instrument are of great beauty, and reveal remarkable structure, which is entirely lost in the ordinary photographs which confuse all levels in a single

blurred impression. The highest level is given by photographs taken in the red line of hydrogen Ha: these show feather-like clouds, whirling vortices, and long narrow black markings which are now known to belong to the red prominences seen projected on the disc. The vortices are of special interest because of their connexion with sunspots; in most cases a sunspot occupies the trough of each whirlpool or whirlwind. If the whirling matter is electrically charged it should act like a solenoid and produce a magnetic field of force; and this consideration led G. E. Hale (1) to test whether a magnetic field could be detected in sunspots. When light is emitted or absorbed in a magnetic field each spectral line is broken up into two or more components--the wellknown Zeeman effect; in particular, for light travelling along the lines of force, the spectral line is replaced by two components circularly polarized in opposite directions. Applying the test for circular polarization clear evidence of the magnetic field in solar vortices was obtained. In general the field strength indicated in a sunspot is of the order 2,000 or 3,000 gausses. It is probably owing to the Zeeman effect that a large proportion of the lines observed in sunspots are observed to be slightly broadened.

An attempt to find a law governing the magnetic polarity of sunspots has not been very successful. On the earth, cyclones have a right-handed or left-handed rotation according to the hemisphere, but there is no such regularity on the sun. There is some evidence that the predominant magnetic polarity in each hemisphere became reversed after the sunspot minimum of 1912. It is surprising to find that there is not even a uniform connexion between the polarity of the spot and the direction of rotation of the whirlwind above it. One very general law is, however, recognized. It was pointed out by Carrington that sunspots very frequently occur in pairs, the line joining them being approximately parallel to the sun's equator; now in these pairs the two spots are found to have opposite polarity. Even when the spot group is more complex a similar bipolarity is generally observed; Hale estimates that in 90% of the spot groups the disturbed area exhibits this bipolar structure.

The detailed explanation of these phenomena is difficult. If the magnetic field is due to the whirling of electrically charged gases, strong electric fields should be present; but the attempt to detect electric fields by the Stark effect on the spectral lines has failed. It seems to be a general belief that the origin of the whole disturbance is a vortex filament below the surface, whose two ends come to the sun's surface near the front and rear of the spot group and give rise to the opposite polarities there.

The method of detection of magnetic fields by the Zeeman effect, has been extended by Hale (2) to a determination of the general magnetic field of the sun (i.e. apart from the exceptionally disturbed regions indicated by sunspots) analogous to the terrestrial magnetic field. It is found that the magnetic axis of the sun deviates from the rotation axis, though not so widely as happens on the earth; the inclination of the two axes is 6°. The synodic period of rotation of the magnetic axis is 3144 days. If we could assume that the source of the sun's magnetic field is a permanent magnetization of its interior, this would give the real rotation period of the sun-a quan tity hitherto unknown. Hitherto our study of the sun's rotation has been based entirely on the surface markings, and these revolve at different rates according to their latitude; the period 31.5 days corresponds to that of surface markings in latitude 55°. It may, how ever, be doubted whether the source of the sun's permanent field lies very deep below the surface; it is found that it diminishes very rapidly as we ascend in level, decreasing from 50 to 10 gausses in about 400 km. The field appears to differ in other respects from that due to a uniformly magnetized sphere, being relatively too strong near the equator; but this is not quite certain.

The value of the constant of solar radiation which is now generally accepted is that determined by C. G. Abbot, viz. that outside the earth's atmosphere the amount of solar energy crossing each sq. cm. of surface is 1.93 gram-calories per minute. This is the same as we should receive if the sun were a black body at a temperature of 5.850° C. (absolute), which may accordingly be taken as the effective temperature of the photosphere. (The definition of effective tempera ture by different writers is unfortunately not uniform; and some would make the term refer to the quality instead of the quantity of the radiation.) The total radiation of the sun is 3.8, 103 ergs per second. The sun's radiant energy differs considerably in composition from black body radiation; and much work has been done on the distribution in wave length of the energy, and the difference in intensity and composition of light received from the centre and the edge of the sun's disc. By comparing observations of the solar radiation made simultaneously at Mount Wilson (California) and Bassour (Algeria) in 1911 and 1912, Abbot (3) believed he had obtained evi dence of an irregular variability of the sun ranging over 10% in the taneously at the two widely separated stations, terrestrial causes course of a few months; since the same variations appeared simul

seemed to be excluded. But this supposed variability of the sun is disproved by Guthnieck and Prager's (4) photoelectric measurements of the brightness of the planet Saturn. The planet, being illuminated by sunlight, would reflect any changes in intensity of the sun's radiation; the delicate measures possible with photoelectric cells showed that the light is very steady, variations of the amount determined by Abbot being quite excluded.

Solar System (see 25.357).-A ninth satellite of Jupiter was discovered by S. B. Nicholson at the Lick Observatory in 1914. Like the eighth satellite it revolves round the planet in the opposite direction to the other seven. The periods of satellites VIII. and IX. are about 739 and 745 days respectively, and the two bodies are revolving in almost equal interlocked orbits in planes inclined at about 10°. Satellites VI. and VII. form a somewhat similar interlocked pair, their periods being 251 and 260 days respectively; but their motions are in the direct"

sense.

Much interest has been taken in the "Trojan Group" of minor planets. These illustrate a special case of the problem of three bodies discussed by Lagrange, viz. that in which the three bodies are situated at the vertices of an equilateral triangle. The Trojan planets have almost the same mean distance and revolution period as Jupiter, and the equilateral condition is roughly fulfilled. The problem of the small librations of such a planet about the triangular point of equilibrium has been discussed by E. W. Brown (5); the condition of stability is that the mass of Jupiter must be less than 0385 times that of the sun -a condition which is easily satisfied-and the period of the libration is about 140 years. Actually the Trojan planets are at some considerable distance from the triangular points, and the problem of determining the finite librations (as opposed to infinitely small librations) has provided much exercise for mathematicians. Six members of the group are now known, Nos. 588 Achilles, 617 Patroclus, 624 Hector, 659 Nestor, 884 Priam, and 911 (unnamed); of these Patroclus and Priam are near the triangular point 60° behind Jupiter, and the others 60° ahead of Jupiter.

A very curious minor planet was discovered by W. Baade on Oct. 31 1920, temporarily designated 1920 HZ. Its orbit is extremely elliptical (eccentricity 0.65); and its perihelion lies near the orbit of Mars, whilst its aphelion reaches to near the orbit of Saturn. It is generally thought that a body with this eccentricity must necessarily be, or become, a comet, the extreme alternations of heat provoking the disruption characteristic of comets; but HZ shows no signs of a cometary envelope, and is provisionally classed as a planet.

The period of rotation of Uranus round its axis has been determined by V. M. Slipher from measures of the line of sight velocity of the advancing and receding limbs. The result is 10h 50m and the direction of rotation agrees with that of revolution of the satellites. Leon Campbell subsequently found that the light of the planet is variable with the same period, presumably owing to unequal brightness of different parts of the surface. The rotation period of Venus still remains a mystery; and there are advocates of the long period of 224 days as well as various estimates of short period (one to three days).

Latitude Variation (see 16.267).-The study of the small periodic motion of the earth's axis of rotation (relatively to the earth) which gives rise to "variation of latitude" has been continued at the six international stations (reduced in number during the later stages of the World War). The effect is made up of (a) The free precession of a spheroid rotating about an axis which does not coincide with its axis of figure; the period of this precession determined from the observations is 4324 days; (b) an annual term, which is a forced oscillation due to meteorological and seasonal causes. Owing to interference of these two terms, there is an effect analogous to "beats" in sound waves, the amplitude of the motion alternately rising to a maximum of about 0"-3 (30 ft.) and dying out in about six years' period. The annual term appears to be nearly circular (6) and of amplitude o" 085; the possible causes contributory to this, such as seasonal circulation of the atmosphere and ocean, snowfall, and vegetation have been investigated by H. Jeffreys (7), who

finds a fair agreement between predicted and observed values. A mysterious Kimura or Z term, which appears in these international results, would, if interpreted literally, indicate an annual approach to the pole and recession by all stations on the same latitude simultaneously-or a shifting of the earth's centre of gravity to and fro along its axis. It is, however, now believed that the term arises from a small systematic error in the observations; independent observations made at Greenwich and Pulkovo (not belonging to the international chain) show either a reduced or zero Kimura term.

The Stars (see 25.784).-Progress in our knowledge of the stellar universe must depend largely on the patient accumulation of accurate statistics as to the parallaxes, motions, spectra, magnitudes, etc., of large numbers of stars; it may therefore be well to review the great advance in these data in recent years. The first photographic determinations of stellar parallaxes reaching a modern standard of accuracy were made by H. N. Russell and A. R. Hinks at Cambridge, and F. Schlesinger at Yerkes, in 1903-7; earlier results are now superseded except for a few of the best heliometer measures made chiefly by Gill. Extensive programmes have since been carried out with large telescopes at the Allegheny, Greenwich, Leander McCormick, Mount Wilson and Sproul observatories, and by 1921 parallaxes of about 1,600 stars had been measured with probable errors generally not greater than o" o1. The use of a rotating sector to reduce the brightness of the star under observation to that of the comparison stars has made a considerable improvement in the accuracy. Unfortunately it does not follow that we know the distances of 1,600 stars, for many of these parallaxes turn out to be inappreciable. The results emphasize the fact that very few of the stars are sufficiently near for the method to give any close measure of the distance; and a large proportion of the measures are of little use individually though they may throw light on questions of statistical distribution when taken in conjunction with other evidence. We cannot resist the impression that investigation of stellar parallaxes by the trigonometrical method is reaching its limit with present instruments; and perhaps for that reason special interest is attached to a new method of determining the distances of stars described below under "Spectroscopic Parallaxes."

Lewis Boss's Preliminary General Catalogue of 6,188 Stars published in 1910 has been an invaluable aid to research with regard to proper motions. It comprises all the brighter stars, and the proper motions constitute a great improvement as regards both accidental and systematic error on anything previously available. Of other catalogues the most notable is the Greenwich 1910 catalogue containing the proper motions of 12,368 stars in the zone Decl. +24° to 32°; the accuracy, of course, does not equal that of Boss's catalogue, but it carries our knowledge of the motions of stars in this region as far as the ninth magnitude. We have still very little systematic knowledge of the motions of still fainter stars, which can be measured photographically; attention has chiefly been directed to the detection of exceptionally large motions by the "blink" microscope or by other methods.

The first really extensive lists of radial velocities were published by the Lick Observatory in 1911. At present (1921) about 2,070 have been determined; these have been collected in a catalogue by J. Voûte. Progress would have been more rapid but for the large proportion of spectroscopic binaries, which makes it necessary to repeat the measures several times at suitable intervals in order to discriminate between orbital

motion and the true secular motion which is looked for. Orbits of 172 spectroscopic binaries are known; and in addition there are about 450 spectroscopic binaries with orbits as yet undetermined. It appears therefore that approximately one-quarter of the stars examined have proved to be spectroscopic binaries. Allowing for systems of wider separation (not detected by varying radial velocity) the actual proportion of binaries must be still higher.

The apparent magnitudes of stars range from -1.5 for Sirius, to 20 and upwards for stars obtained by long exposures with the