i 9 6 SCIENCE PROGRESS* 



E. H. Neville (Proc. Cambridge Phil. Soc, 1919, 19, 234-7) 

 proves, in a form purely intrinsic, the relation discovered by- 

 Bonnet between the integral curvature of a bounded region on 

 any bifacial surface and the integrated geodesic curvature of 

 the boundary. 



On geometry cf. W. Blaschke (13), F. Schuh (49), G. C. A. 

 Koopmans (50), V. Th^bault (36, 37), A. Auric (36), De Pulligny 

 (33), M. Brillouin (32), H. Wolff (31), R. Lohnstein (31), W. A. 

 Wythoff (46), M. Pasch (21), E. Kruppa (14), N. Agronomof 

 (37), R. Bricard (34, 36), P. Appell (36), R. Goormagtigh (36, 

 two papers), R. Sturm (29, two papers), W. A. Versluys (46, 

 49), M. Weill (36), F. Balitrand (36), A. Myller (36), G. Darboux 

 (35), A. Buhl (35), H. du Bois (12), R. de Montessus de Ballore 

 (32), B. Giovanni (44), C. Segre (44), H. Mohrmann (19, 23), 

 E. Miiller (12), S. Jolles (24, 28), T. Reye (24), L. Braude (12), 

 P. Tortorici (44), R. Bouvaist (36), K. Popoff (12), C. Guichard 

 (32), H. Vermeil (20), E. Magin (12), J. de Vries (44, 45, two 

 papers), C. H. van Os (46), J. Andrade (34), B. P. Hallmeijer 

 (44, 46), A. D. Fokker (46, 50), A. Denjoy (45, 46), A. Winter- 

 nitz (28), H. Berliner (22), J. A. Schouten (44, 45), and 

 J. Arnovlievitch (36). 



ASTRONOMY. By H. Spencer Jones, M.A., B.Sc, Royal Observatory, 



Greenwich. 



The Parallactic Motions of the Stars. — Astronomers are under 

 a great obligation to Prof. Kapteyn and his collaborators at 

 the Astronomical Laboratory at Groningen for their valuable 

 discussions of large masses of statistical material bearing upon 

 the arrangement of the stars in space. They have shown a 

 remarkable skill in dealing with diverse results, and though 

 some of their earlier conclusions were based upon compara- 

 tively scanty material, there has been no reason to doubt their 

 substantial accuracy. Of recent years, largely through the 

 development of new methods, much additional material has 

 accumulated. Thus, in Groningen Publications, No. 8, the 

 determination of the sun's velocity was based upon the radial 

 velocities of only fifty-one stars. Reliable determinations are 

 now available for nearly two thousand. As regards directly 

 determined, or trigonometrical parallaxes, our knowledge is 

 accumulating at a remarkable rate, and is probably at least 



