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296 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 War- fare Department of the Ministry of Munitions, and in 1919 con- troller, 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 1 6 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, 1ST VISCOUNT (1848- 1919) [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 suc- ceeded to the viscountcy, Lady Astor, who had taken much interest in the local affairs of her husband's former constitu- ency 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.

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 photo- graphs 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 (i) to test whether a magnetic field could be detected in sunspots. When light is emitted or absorbed in a magnetic field each spec- tral line is broken up into two or more components the well- known 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 in- dicated 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 sun- spots 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 mag- netic 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 31-44 days. If we could assume that the source of the sun's magnetic field is a permanent magnetization of its in- terior, 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 cor- responds 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 I -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 temperature 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, io 33 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 evidence of an irregular variability of the sun ranging over 10% in the course of a few months; since the same variations appeared simultaneously at the two widely separated stations, terrestrial causes