Substituting the values of c and de in terms of c' and de' obtained from (7) we get Integrating this equation we get p' as a function of c', i. e., of yC; substituting this in (2) we get P and from (6) in the form T In order to draw the curve of fig. 1 the integral was evaluated graphically using the constants given by Kraus and Bray. XXV. Notices respecting New Books. Researches of the Department of Terrestrial Magnetism. Vol. III. Ocean Magnetic Observations 1905-1916, and Reports on Special Researches. By L. A. BAUER, Director, Washington D.C. Published by the Carnegie Institution of Washington, 1917. Quarto, pp. v+447, with 25 plates and 35 figures in the text. THIS THIS volume is issued also in three parts, dealing respectively with the earlier magnetic observations taken at sea by the 'Galilee' 1905-1908, the later sea magnetic observations by the Carnegie' 1909-1916, and the results of the observations on Atmospheric Electricity taken on both vessels. There is a very full account of the instruments, the methods of observation and the reduction formulæ, and elaborate tables of results and particulars of the errors in existing charts-American, British, and German. The vessels and the instruments are illustrated in the plates from a variety of points of view. The observing vessel 'Carnegie' was specially built for magnetic work and is almost free from magnetic material. This has proved a great simplification in the reduction of the observations. Published the First Day of every Month.-Price 2s. 6d. APR 4 1918 THE UNLONDON, EDINBURGH, AND DUBLIN PHILOSOPHICAL MAGAZINE, AND JOURNAL OF SCIENCE. Being a Continuation of Tilloch's Philosophical Magazine,' Nicholson's 'Journal,' and Thomson's 'Annals of Philosophy.' CONDUCTED BY SIR OLIVER JOSEPH LODGE, D.Sc., LL.D., F.R.S. SIR JOSEPH JOHN THOMSON, O.M., M.A., Sc.D., F.R.S. JOHN JOLY, M.A., D.Sc., F.R.S., F.G.S. GEORGE CAREY FOSTER, B.A., LL.D., F.R.S. AND WILLIAM FRANCIS, F.L.S. SIXTH SERIES. N° 207.-MARCH 1918. WITH FOUR PLATES. Illustrative of Prof. R. W. WooD's Paper on Resonance Spectra of Iodine; and Dr. G. W. TODD's on General Curves for the Velocity of Complete Homogeneous Reactions between Two Substances at Constant Volume. LONDON: PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. Sold by Simpkin, Marshall, Hamilton, Kent, and Co., Ld.:-Smith and Son, Glasgow:-Hodges, Figgis, and Co., Dublin:-and Veuve J. Boyveau, Paris. CIRCULATING LIBRARY OF THEORETICAL AND APPLIED SCIENTIFIC AND TECHNICAL BOOKS COVERING THE WIDEST RANGE OF SUBJECTS. NEW WORKS AND NEW EDITIONS ARE ADDED TO THE LIBRARY IMMEDIATELY ON PUBLICATION. ANNUAL SUBSCRIPTION, TOWN OR COUNTRY, FROM ONE GUINEA, according to the number of books required at one time. Subscriptions may begin at any date. Books may be retained as long or exchanged as frequently as desired. Prospectus, with Quarterly List of Additions, post free. BOOKSELLING DEPARTMENT. Complete Stock of Recent Works and Text-Books in all Branches of Science and echnics. Special facilities for execution of Orders from Abroad. Effectually protective packing used without charge. H. K. LEWIS & CO. LTD. and 24 136 Gower Street, Gower Place, London, W.C. 1. Metropolitan Railway: Euston Square Station. All Tube Railways: Warren Street. Telegrams: Publicavit, Eusroad, London."' Demy 8vo, with numerous Woodcuts. Price 6s. AERONAUTICS. Br G. BREWER AND P. Y. ALEXANDER. TAYLOR AND FRANCIS, Red Lion Court, Fleet Street, E.C. 4. Mr. H. A. COLLINS, 32 Birdhurst Road, Croydon. THE LONDON, EDINBURGH, AND DUBLIN PHILOSOPHICAL MAGAZINE AND JOURNAL OF SCIENCE. [SIXTH SERIES.] MARCH 1918. XXVI. Rain, Wind, and Cyclones. URING recent years our conceptions respecting the conditions obtaining in cyclones have undergone very considerable alterations. The old idea, which made a cyclone consist of a lower spirally inflowing current of air directed towards the centre of an area of low barometric pressure, an internal rising current of warm air, and an upper stream of air flowing outwards from the same area, requires very considerable modification in view of modern discoveries. That the cause of rain is due to the upward flow of masses of air, which being cooled below the dew-point by expansion, condense out some of their moisture, still holds true; but the distribution of temperature and the actual nature of the air circulation prove to be very different from what was once thought to be the case. In all scientific work accurate observation and correct records are essential. Here, however, meteorological records fail us in a very important particular. The wind directions shown on our charts are not always accurate. In Great Britain, for example, wind directions are given to the nearest of sixteen points of the compass. It thus comes about that winds which are observed to differ in direction only one or two degrees from each other, may be charted as differing by as much as twenty degrees. *Communicated by the Author. Phil. Mag. S. 6. Vol. 35. No. 207. March 1918. R Owing to the direct flow of the wind being prevented by trees, buildings, hills, &c., it is by no means easy to observe the correct direction of movement. It often happens that a wind blowing up a river will follow closely the river windings; passing clouds, especially rain-clouds, also produce, for short intervals, marked changes both in the direction and force of the wind; but the difficulties that are met with in observing the general direction should be overcome by the exercise of extreme care so as to obtain a result as accurate as possible. The observed results should then be recorded in degrees from the true north, working clockwise round the compass. To render the points I wish to draw attention to clear, a number of charts or diagrams of cyclonic disturbances &c. have been taken from Shaw and Lempfert's paper on "The Life History of Surface Air Currents". The wind directions are sometimes shown by continuous lines instead of arrows, and the isobars by dotted lines. In the original charts the arrows often show many irregularities in the wind directions of the same wind province; but these are due to local causes such as hills, falling rain, &c. It is near the centres of cyclones that the errors arising from the methods of observation now adopted appear to be most marked. Indeed, until strict accuracy is arrived at in recording and plotting observations of wind directions, many features of atmospheric circulation will continue to be obscure. Shaw and Lempfert, in the paper already referred to, show that the wind directions in cyclones, if they do not always close in as regular spirals towards the cyclonic centre, do travel in such a way that the air suffers horizontal contraction and rises. That this is the case is rendered evident by the consideration of the air trajectories they have worked out. In the case of quite a deep cyclone the difference of pressure between the centre and the margin seldom amounts to more than one inch of mercury, and this is about the change of pressure due to a rise of 400 feet. To give rise to heavy rain, masses of land over which winds are blowing and rising as they advance must be much higher than this. In a cyclone the rain-producing effect resulting from the fall of the barometer is very small indeed. Rain when it does fall nearly always results from the rise of air in the cyclone or the mounting of one air current over another, the quantity of rain depending upon the humidity of the rising air and the height to which it is lifted. According to the old view, the air rises spirally in the *Meteorological Office Publication No. 174. |