420 



NATURE 



[July 19, 1917 



Sir George Greenhill : The Rankine trochoidal wave. 

 The Rankine trochoidal wave (Phil. Trans., 1863), 

 either as rollers or as a starting wave, can be divided up 

 by vertical planes perpendicular to the wave crest into 

 compartments, and the compartments sheared along 

 each other. The investigation is made of the extra 

 field of force in addition to gravity when the shear is 

 made continuous and the planes removed in order 

 that the continuity of pressure should be preserved in 

 the interior of the water, and for the new wave motion 

 to persist. Also when the planes stand over to the 

 vertical and the circular orbits in the roller are in 

 parallel planes. A geometrical investigation is added 

 of the molecular rotation in the .interior of the Rankine 

 wave. — Dr. P. E. Shaw : The tribo-electric series, 

 (i) The tribo-electric series, in which solid materials 

 are arranged in order according to the charge they 

 acquire when rubbed together, is trustworthy with 

 due precautions. (2) Most solids are found to alter 

 their place in the series if heated above a certain 

 temperature which is specific for each material. This 

 terhperature is called the critical temperature. The 

 surface in its new condition is termed abnonnal. (3) 

 The series may be divided into an upper Group A 

 and a lower Group B. It is found that these groups 

 have tendencies contrary to one another as the sur- 

 faces of the materials are rendered (a) matte, or (b) 

 abnormal, or (c) pressed, or (d) flexed. If under any 

 of these agencies Group A becomes more + forming, 

 Group B becomes more — forming, and vice versa. 

 (4) Anomalous effects are observed when liquid mer- 

 cury is used as one of the materials, its behaviour 

 being quite unlike that of solid surfaces. (5) As to 

 theory, it is suggested that the prevalent idea that 

 the electric double-layer existing at the surface of 

 solids has the — layer outermost in all cases is incor- 

 rect. Normally the materials in Group A would have 

 — outermost, those in Group B having + outermost. 

 Orientation of surface atoms would give rise to 

 changes in the disposition of the two electric layers 

 and so account for observed effects. (6) Tribo-elec- 

 tricity undoubtedly affords a means, of extraordinary 

 delicacy, of discriminating between materials appar- 

 ently alike. Two instances are seen in the group of 

 furs and the group of woods. — J. J. Nolan: The nature 

 of the ions produced by the spraying of water. Part i. 

 gives an account of the determination of the mobili- 

 ties of the very mobile ions produced by the spraying 

 of water. Groups of ions are found, positive and 

 negative, some of very high mobility. In part ii. the 

 less mobile ions described in a previous paper are 

 discussed. Treating the ions as minute spheres of 

 water, it is shown that their sizes as deduced from 

 an empirical modification of Stokes's law would agree 

 with the sizes calculated from the ordinary theoretical 

 mobility formulae. Certain evidence, however, tends 

 to show that the larger of these ions are not simple 

 spheres of water, but that they consist of loose group- 

 ings of various numbers of some smaller water- 

 globules. In part iii. it is shown that the V3ry mobile 

 ions can be accounted for by supposing that they 

 consist of aggregates of various numbers of water- 

 molecules, the numbers of molecules in the various 

 ions being related to one another in a regular way. 

 Some of these ions have the same mobility as ions 

 produced in air by X-rays, etc. It is suggested that 

 the ordinary gaseous ion consists of a group of water- 

 molecules, the size of the group depending on the 

 degree of moisture of the gas. — Prof. J. C. McLennan : 

 The absorption spectra and the ionisation potentials of 

 calcium, strontium, and barium. — J. Small : Geo- 

 tropism and the Weber-Fechner law.— Prof. W. B. 

 Bottomley : The isolation from peat of certain nucleic 

 acid derivatives. 



NO. 2490, VOL. 99] 



BOOKS RECEIVED. 



Spiritualism and Sir Oliver Lodge. By Dr. C. A. 

 Mercier. Pp. xi+132. (London: Mental Culture 

 Enterprise.) 45. 6d. net. 



A Manual of Field .Astronomy. By A. H. Holt. 

 Pp. X+128. (New York: J. Wiley and Sons, Inc.; 

 London : Chapman and Hall, Ltd.) 6s. net. 



Liiboratory Manual of Bituminous Materials for the 

 Use of .Students in Highway Engineering. By Pre- 

 vost Hubbard. Pp. xi+153. (New York: John "Wiley 

 and Sons, Inc.; London: Chapman and Hall, Ltd.) 

 6s. net. 



The Fundus Oculi of Birds, especially as Viewed by 

 the Ophthalmoscope. By Casey Albert Wood. Pp. 

 180 -h plates 1x1. (Chicago: The Lakeside Press.) 



Fifty-fifth Annual Report of the Secretarj- of the 

 State Board of Agriculture of the State of Michigan 

 and Twenty-ninth Annual Report of the Experiment 

 Station from June i, 1915-June 30, 1916. Pp. 896. 

 (Lansing, Mich. : Wynkoop Hallenbeck Craw^ford Co.) 



Critique des Propulseurs. Par Paul Popovatz. Pp. 

 131. (Paris : Gauthier-Villars et Cie.) 



Science and Industry. The Place of Cambridge in 

 any Scheme for their Combination. The Rede Lec- 

 ture, 1917. By Sir R. T. Glazebrook. Pp. 51. (Cam- 

 bridge : At the University Press.) is. 6d. net. 



TRe National University of Ireland. Calendar for 

 the Year 19 17. Pp. viii + 579.. (Dublin : A. Thom and 

 Co., Ltd.) 



The Biology of Waterworks. By R. Kirkpatrick. 

 (Economic Series. No. 7.) Pp. vi + 58. (London: 

 British Museum, Natural History.) 



CONTENTS. ^^ 



Acromegaly and the Extinction of Species. By 



Prof. A. Keith, F.R.S. .... 401 



Electrotechnical Books. By Dr. A. Russell .... 401 



Our Bookshelf . .... 403 



Letters to the Editor: — 



Radiation-Pressure, Astrophysical Retardation, and 



Relativity. — Sir Joseph Larmor, F.R.S., M.P. . 404 



Oceanic Tidal Friction. — Harold Jeffreys ... 405 



Gravitation and Thermodynamics. — ^J. S. G. Thomas 405 



The First New Moon in the Year i B.C. — Dr. Otto 



Klotz . . . . . . . 405 



Photographs of Aurora. {Illustrated.) By Dr. C. 



Chree, F.R.S 405 



The Dye Problem among the Entente Powers. By 



Prof. G. T. Morgan, F.R.S. . ... 406 



France and National Scientific Research Applied 



to Industry. By E. S. Hodgson 408 



Notes 408 



Our Astronomical Column :— 



The Relativity Theory and the Motion of Mercury's 



Perihelion • . 412 



Anomalous Dispersion . 413 



The Variable Star « Herculis 413 



The Future of the Disabled ..... 413 



Refractories Used in the Iron and Steel Industry. 



By H. C. H. C 413 



The Complexity of the Chemical Elements. By 



Prof. Frederick Soddy, F.R.S 414 



University and Educational Intelligence .418 



Societies and Academies 419 



Books Received ... 420 



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