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Series A.—Mathematical and Physical. 
A 579. A Determination of the Deflection of Light by the Sun’s Gravitational Field, from Observations 
made at the Total Eclipse of May 29, 1919. By Sir F. W. Dyson, F.R.S., Astronomer Royal, 
Prof. A. S. Eddington, F.R.S., and Mr. C. Davidson. Pp. 43; 1 Plate. Price 4s. 6 d. 
A 580. A Critical Study of Spectral Series. Part Y.—The Spectra of the Monatomic Gases. By 
W. M. Hicks, F.R.S. Pp. 134 ; 4 Plates. Price 8s. 
A 581. Title, Contents, Index, &c., Vol. 220. Pp. 10. Price 6 d. 
Volume 220 (1920), 470 pp., with 5 Plates, Price £2 4s. 
A 582. Some Measurements of Atmospheric Turbulence. By Lewis F. Richardson. Pp. 28; 1 Plate. 
Price 3s. 6d. 
A 583. On a Theory of the Second Order Longitudinal Spherical Aberration for a Symmetrical Optical 
System. By T. Y. Baker, B.A., Instructor Commander, R.N., and L. N. G. Filon, M.A., 
D.Sc., F.R.S., Goldsmid Professor of Applied Mathematics and Mechanics in the University 
of London. Pp. 43. Price 3s. 6 d. 
A 584. Investigations on Lightning Discharges and on the Electric Field of Thunderstorms. By 
C. T. R. Wilson, F.R.S., Reader in Electrical Meteorology in the University of Cambridge 
and Observer in Meteorological Physics at the Solar Physics Observatory, Cambridge. 
Pp. 43; 4 Plates. Price 5s. 
A 585. Researches on the Elastic Properties and the Plastic Extension of Metals. By W. E. Dalby, 
F.R.S., Professor of Engineering at the City and Guilds (Engineering) College of the Imperial 
College of Science and Technology. Pp. 22. Price 3s. 6d. 
Series B. — Biological. 
B 369. The Morphology and Evolution of the Ambulacrum in the Echinoidea Holectypoida. By 
Herbert L. Hawkins, M.Sc., F.G.S., Lecturer in Geology, University College, Reading. 
Pp. 104 ; 9 Plates. Price 8s. 6 d. 
B 370. On the Structure of Lysorophus, as Exposed by Serial Sections. By W. J. Sollas, Sc.D., 
F.R.S., Professor of Geology in the University of Oxford. Pp. 47 ; 1 Plate. Price 7s. 6 d. 
B 371. Title, Contents, Index, &c., Vol. 209. Pp. 10. Price Gd. 
Volume 209 (1920), 530 pp., with 70 Plates, Price £3 13s. 
B 372. The Respiratory Exchange of Man During and After Muscular Exercise. By J. M. H. Campbell, 
O.B.E., B.M., C. Gordon Douglas, C.M.G., M.C., D.M., Fellow of St. John’s College, Oxford, 
and F. G. Hobson, D.S.O., B.M. Pp. 47. Price 5s. 
B 373. The Microscopical Features of Mechanical Strains in Timber and the Bearing of these on the 
Structure of the Cell-wall in Plants. By Wilfrid Robinson, D.Sc., Lecturer in Botany, 
University of Manchester. Pp. 34; 4 Plates. Price 5s. 
B 374. On a Form of Botrytis cinerea , with Colourless Sclerotia. By William B. Brierley (Roth- 
amsted). Pp. 31; 1 Plate. Price 4s. 
B 375. The Irish Eskers. By J. W. Gregory, D.Sc., F.R.S. Pp. 37. Price 4s. 
Bf376. The Thermo-Elastic Properties of Muscle. By A. V. Hill, F.R.S., and W. Hartree. Pp. 21. 
Price 2s. 
Cloth cases for binding the volumes of the. ‘ Philosophical Transactions.’ Price 3s. 6 d. 
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