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932 is given in The Computer's Handbook, M.O. 223, Section II., Subsection III. Shaw has in these papers emphasized the rule that at all heights save close to the surface the path of the air particle will be along the line in which the isobaric and the geo- potential surfaces intersect. The rule is admittedly not exact, and it applies only to cases of steady motion; its general accept- ance is probably due to two considerations. It has been found by practical work that in laying down the direction and velocity of the wind at one or two km. height (in the absence of definite information from pilot balloons) for the use of aircraft the best that can be done is to give the gradient wind, and it is not certain that the actual wind at 500 metres differs from the gradient wind by a greater amount than is due to the errors of observation. Secondly it is apparent that a depression could not be maintained for hours together with an approximate uniformity of pressure if air were continuously passing into it or out from it; quite a trifling wind blowing systematically into an ordinary depression for a few minutes would suffice to fill it up. Hence one is led to the conclusion that the strong winds that surround a depression must in general blow along the isobaric lines.

In his Manual of Meteorology, Part IV, M.O. 234, Napier Shaw has also provided a valuable account of the " relation of the wind to the distribution of barometric pressure."

In connexion with the subject of forecasting, Prof.. V. Bjerknes' theory of the " polar front " must be referred to. His suggestion is that cyclones are caused by the discontinuity between polar and equatorial air, that, provided the network of stations is sufficiently close, the line where the surface of discontinuity meets the earth's surface can be traced on a chart, and the cyclone will move in the direction of a line he calls the steering line. Prof. Bjerknes' views are in the Q. J. Met. Soc., April 1920, vol. xlvi., No. 194, p. 119.

A ntarctic Meteorology. Great additions to our knowledge of the meteorology of the Antarctic regions were made by the publica- tion of the results of Scott's Antarctic expedition of 1911. The observations were taken mostly by Dr. Simpson, who has worked them up and discussed the various problems which had been left in a more or less uncertain condition by previous expeditions. He has greatly extended our knowledge both from the observational and theoretical sides. It must suffice to state here that amongst other matters Dr. Simpson has established the anticyclonic character of the weather in the Ross Sea area, and has shown that the blizzards are not due to the passage of cyclones from W. to E. over the Antarctic Ocean.

See W. N. Shaw, Forecasting Weather (1911); Willis L. Moore, Descriptive Meteorology (1911); C. J. Plave, The Structure of the Atmosphere in Clear Weather (1912) ; Dr. Julius Hann, Handbuch der Klimatologie (3rd ed. 1911); V. Bjerknes and others, Dynamische Meteorologie und Hydrographie (Carnegie Institute of Washington, 1912); H. N. Dicksoh, Climate and Weather (1912); Dr. Alfred Wegener, Thermodynamik der Atmosphdre (1911); M. VV. Campbell Hepworth, National Antarctic Expedition 1901-1904 (London, Royal Society, 1913) ; Ice Observation, Meteorology and Oceanography in the North Atlantic Ocean (Report on the work carried out by the S.S. " Scotia," 1913); G. E. Abbot, F. E. Fowle and L. B. Aldrich, " New Evidence on the Intensity of Solar Radiation outside the Atmosphere " (Smithsonian Miscellaneous Collections, vol. Ixv., No. 4) ; Dr. Gilbert J. Walker, " Correlations in Seasonal Variations of Weather " (Memoirs of the Indian Meteorological Department, vols. xx. and xxi.) ; Anders Angstrom, " A Study of the Radiation of the Atmosphere " (Smithsonian Miscellaneous Collections, vol. Ixv., No. 3, 1915); G. C. Simpson, British Antarctic Expedition 1910- 1913, Meteorology, vol. i. Discussion, vol. ii. Maps and Curves (1919); W. J. Humphreys, Physics of the Air (pub. for the Franklin Inst., 1920) ; F. N. Exner, Dynamische Meteorologie (1917) ; R. G. K. Lempfert, Meteorology (1920); L. J. Richardson, Forecasting the Weather by Numerical Computation (1921); the Geophysical Memoirs (pub. by the Meteorological Office) ; the Meteorological Glossary (fourth issue, M.O. 225.11, the Meteorological Office).

(W. H. Di.) METHUEN, PAUL SANFORD, 3RD BARON (1845- ), British field-marshal (see 18.298), was born Sept. 1 1845, joined the Scots Fusilier Guards in 1864, served in the Ashanti War of 1874, the Egyptian Expedition of 1882 and the Bechuanaland Expedition of 1884-5. As a major-general he served in the Indian Frontier War of 1897-8, shortly after which he was promoted lieutenant-general. On the outbreak of the South African War he went out in charge of the ist Division, which he commanded at Belmont, Enslin, Modder river and Magersfontein; he remained in the field, engaged constantly on active operations and holding various commands, until just before the end of the conflict when he was, in March 1902, dangerously wounded and taken prisoner at Tweebosch; he was rewarded with the K.C.B. and the G.C.B. for his services in the war. He was in charge of the Eastern Command from 1904, in which year he was promoted general, until 1908, and he then went out as commander-in-chief to South Africa 1908-9. In 1911 he was promoted field-marshal. During the greater part of the World War he was governor of Malta. In 1919 he became Constable of the Tower. MEUSE-ARGONNE, BATTLE OF (Sept.-Nov. 1918). The general idea of the Meuse-Argonne attack was agreed upon in a conference between Marshal Foch, Gen. Petain and Gen. Pershing at Bombon, on Sept. 2. What Foch really desired and had urged upon Pershing in a conference three days previous was to break up the American army, as an offensive force, immediately after the projected St. Mihiel attack, and to employ the best of its troops to reinforce the II. and IV. French Armies for a combined offensive along the front of these two armies. But Pershing firmly opposed the breaking-up of his army and insisted upon adherence to the original design of employing the main part of the American troops as an integral army unit. Foch finally acceded and gave Pershing his choice of the sector of the II. Army (from the Meuse to the Argonne, inclusive) or that of the IV. Army (from the Argonne, exclusive, to the Suippe). He chose the former.

Following this conference Foch issued a general directive for the attack, which Petain elaborated into precise orders for the two armies concerned, those of Pershing and Gouraud. The general objective named for the combined attack was Mezieres. The St. Mihiel operation was conceived as a prepar- atory phase (or Operation A.), to give a broader base and better communications for the later operations, notably by freeing for use the railway and roads leading to Verdun from the S. along the Meuse. The American army attack on the front Meuse-Argonne inclusive (Operation B.) and the French IV. Army attack extending from the Argonne W. to the Suippe (Operation C.) were to be simultaneous. Following some days later the French V. Army was to continue the attack W. from Reims to the Aisne (Operation D.).

The direction of attack given for Operation B. was Buzancy-Mezieres, but the first objectives named were the Hindenburg line on the front Brieulles-sur-Meuse-Romagne-sous-Montfaucon-Grandpre. In fact, the French higher leaders did not at that time conceive that the attack could be carried beyond that line before winter. The American army was to be reinforced for Operation B. by 180 French airplanes, 239 French tanks and a considerable force of French artillery (1,002 heavy guns, 456 light guns and 234 trench mortars). In addition a French cavalry division stood by to take advantage of a possible break through the German lines. The American attacking troops consisted of three army corps, having three divisions each in the front line and three divisions in reserve., Only one of these front-line divisions was composed of regular troops, while of the others three of the four National Guard and three of the four National Army divisions employed lacked any previous battle experience.

The newly formed American Army Staff had been a little apprehensive of the 'outcome of its initial attack at St. Mihiel (Operation A.), and had in consequence designated for that attack most of its better-trained and more experienced divisions, including four of the six available regular divisions. Further, more resistance, with consequently heavier losses, was anticipated in Operation A. than proved to be the case, and it had been considered that more time would be required for resting and recruiting the divisions engaged. The results of this policy in the light of after events, turned out to be most unfortunate. Operation A. was a simple attack which, as was expressly ordered by Foch, was not to be exploited even to the extent of attacking the reserve German position across the face of the salient. The Meuse-Argonne attack, on the contrary, was to be