500 



NATURE 



[February 21, 19 18 



343 miles (5-53 km.) at a depth of 400 mjles, 

 and 425 miles (6S4 km.) at depths greater, 

 than 1000 miles.— Prof. W. H . Metzler : A deter- 

 minantal, equation the roots of which are thetproducts 

 of the roots of given equations. — Prof. R. A. Sampson : 

 Studies. in clocks and timekeeping, (i) The theory of: 

 maintenance. This paper, the first of a series of 

 studies which are in course of execution at the Royal' 

 Observatory, Edinburgh, describes in outline the ar- 

 rangements of the thermostat chamber, etc.,. and the 

 construction of the three docks, Riefler 258 j Syn- 

 chronome, and Cottingham, upon which most of the> 

 studies are made. Its- direct occupation is^ however, 

 chiefly theoretical, considering with sufBcient detail, 

 various dynamical points which arise from the sus- 

 pension and different maintenances of the clocks. and, 

 the derivation of a satisfactory- differential equation 

 of, the motion when the.-, internal, resistance, is taken- 

 into account. The solution, of this equation presents 

 s-ome- novelty, showing that the frequency in main- 

 tained mot-ion is dependent upoji the first p.ower of 

 friction, not the second, as has . hitherto been. held.. 

 The discontinuous maintenance is resolved' into a- 

 Fourier series, and expressions are found for calculat- 

 'ing the escapement error and the arc described in 

 each case. In the case of, the three clocks above the 

 calculated arcs are numerically verified by comparison 

 with their actual performance. 



ROOKS' RECEIVED. 



Laboratory Glassware Economy. By Prof. H. B. 

 Dunnicliff. Pp. x + 92.. (London : Macmillan and Co., 

 Ltd.) 45. net. 



Hand Grenades. By Major G. M. Ainslie. Pp. v + 

 59. (New York: J. Wiley and Sons, Inc. ; London : 

 Chapman and Hall, Ltd.) 65. net. 



Text-Book of Ordnance and Gunnery. By Lt.-Col. 

 W. H. Tschappat. Pp. x+705. (New York : J. Wiley 

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

 305. net. 



A Text-book in the Principles of Science Teaching. 

 By Prof. G. R. Twiss. Pp. xxvi + 486. (New York: 

 The Macmillan Co. ; London : Macmillan and Co., 

 Ltd.) 75. 6d. net. 



A Short History of Science. By Prof. W^ T. Sedg- 

 wick and Prof. H. W. Tyler. Pp. xv + 474. (New 

 York : The Macmillan Co. ; London : Macmillan and 

 Co., Ltd.) 125. 6d. net. 



A Text-Book of Physics for the Use of Students of 

 Science and Engineering. By J, Duncan and S. G. 

 Starling. Pp. xxiii+1081. (London: Macmillan and 

 Co., Ltd.) 155. 



Applied Mechanics. Second Year. By H. Aughtie. 

 Pp. 227. (London : G. Routledge and Sons, Ltd.) 

 25. 6d. net. 



Airfare of To-day and, of the Future. By E. C. 

 Middleton. Pp. xv+192.. (London: Constable and 

 Co., Ltd.) 35. 6d. net. 



The Edinburgh School of Surgery before Lister. By 

 A, Miles. Pd. viii4-22o. (London : A. and C. Black, 

 Ltd.) 55. net. 



DIARY OF SOCIETIES. 



THURSDAY, Ffbruary 21. 



R'^vAi. SociETV, at 4,30.— The-Scattering of Iiight by Spherical Sh«ll.s, and 

 by Complete Spheres of Periodic Structure, when the Refractivity is Small; 

 ».ord Rayleieh.— The Nature of Heat as Directly Deducible from the 

 Postulate of Ca-not : Sir lo.seph Larmor.— Curved Beams: T. J. Guest.— 

 (i)l\fonoclinic Double Pelenates of the Iron Group ; (2) Selenic-Acid and. 

 ■ Iron. _ Reduction of Selenic Ac'd bv Na.scent Hydro'jen and Hyd'Ogen 

 Sulphide. Preparation of Ferrous Selenate and Double Selenates of Iron 

 Group t Dr. A. K. H> Tutton 



Institution. OF Electrical Engineers, at 6.— Switchgear Standardisa- 

 tion : Dr. C. C. Garrard. 



Institution of Mining and MF.iAi.LURnv, at 5.30. 



-Recent Studies on Active Nitrogen : Hon. R. J. 



Chemical Societv, at 

 Strutt. 



Linnean Society, at 5. — Notes on the Bionomics, Embryology, and 

 Anatomy.of Ceitaia HymenopteraJPatasi.tifa,. with Special Reference to 

 Micras(LiUr conne^us^'i^cif!,: J. Bcont,^ G.atenby. — Experimental Studies 

 in the Specific Valu« of Morphological Characters in the Fungi: W. I!. 

 Brierley. 



FRIDAY, February 22. 



Phvsical Society, at 5. — Note on the Use of Approximate Method.^ in 

 Obtaimng Constructional Data for Telescopic Objectives : T. Smith. —A 

 Suggesuon. as tQ the Origin of Spectral Serjeg : Dr. H. Stanley All.eni 



SATURDAY, Febj«jaryv23. 

 RovAU Institptjqn, at 3.— Probleres.in Atomic Structure: Si^ J. J,. 

 Thomspn, 



MONDA Fv February 25. 

 Royal Society oy Arts at 4,30..— Th^.Ecpnojnic Condition o£th.?.Umt«4.' 

 Kingdom B.efore-the War: the Real Cost. of ths War, and Ecofjewic,. 

 Reconstruction-: B; Crammond. 

 Royal .GEociBAeHiCAl, Society, at 8i3o.r-A Recentjourney in EastAfrloai - 

 Coinie ReaauJdid«.Briey. 



TUESDAY; February ^6. 

 Royal Institution, at 3. — A National Laboratory of Industrial Resevch; 



Sir R^ T, Gtazebt-ook, 



lu.UMiNATiKKi ENGINEERING SoGiETY,- afi 5,— A'. Survey of Mfth<?ds-.o6- 



Dir?citinj; and Concentrating Light.: Lieivt.,-Con»maoder H, T. HArrispn^ 



WEDNESDAY, FsiBBUARV 27. 



RoYAj, Society of Arts, , at 4.30.— Organisation of Commercial IntelU- 



Sir.W. Hi C)4rkev 



THURSDAY, F^^BRBARY 28: 

 Royal- SooiaiTrj at. 4.30. — Probable /'a/^rj; Scattering of Light by Du^tr ; 

 free Air, with Artificial Reproduction of, the Blue-5iky. Preliminary Note. : 

 The Hon. R. J. Strutt.— The Lommel-Weber €1 Function and its Applica- 

 tion- to the Problem of Electric Waves oa a .Thin Atichor Ring: Dr. J. R. 

 Airey-^nvestigjitions onTextik Fibres : W. Harrison.— ^Critical Lowliag 

 of Struts and Structure ; W. L. Cowley and H. Levy. 



FRIDAY, Uakch I,. 

 RovAL- INSTITUTION, at 5.30. — The Mt>d*rn Dye-stuff 'Industry : P>yof. 

 Ai O. Green, 



SATURDAY.,MhRCn 2. 

 RovAL Institution, at 3. — Problems iu Atomic Structure: Sir J. .J.. 



CONTENTS. PAGE 



Heat-drop Tables. By Sir J. A. Ewing, K.C.B., 



F.R.S. 481 



The Ethnological Value of Shells. By Dr. A, C. 



Haddon, F.R.S A^l 



Marine Biology and Fish Culture . 48.2.; 



Our Bookshelf 483 



Patents and Scientific Research 484 



Precious Stones and Platinum in 1916 486 



Prof. G. A. Lebaur. ByJ. A. S 487 



Dr. John McCrae 487 



Notes I488 



Our Astronomical Column : — 



Relativity and Gravitation . 492 



The System of k Pegasi 492 



Forthcoming Books of Science 492 



Primitiye Cults 494' 



SUlphurJn the United States 494. 



Science^ as a Vehicle, of Education* ByProf. T. 



Bxailsfordj Robertson; 495; 



University and Educational Intelligence 4971 



Societies and Academies 498-' 



Books Received 500- 



Diary of Societies 50Q, 



Bdilocial. and' Duhlishing Offices: 



MACMILLAN AND CO., Ltd., 



ST. MARTIN'S STJ^EBT, LONDON, W.C.2. 



Advertisements and business letters- to he- addressed to the 

 Publishers. 



Editarial, Communications . ta the. Editcr 

 Telegraphic. Address : Piiusis,, London. 

 Telephone . Numher : Gerrard 8830 



NO. 2521, VOL. 100 



