January 26, 1922] 



NATURE 



121 



in atomic weight amounted in different experiments 

 to from slightly less than to considerably more than 

 one part in a thousand. A considerable amount of 

 the isotopic acid has been produced. These experi- 

 ments seem to confirm beyond doubt the existence of 

 the isotopes of chlorine first announced by Dr. Aston 

 on the basis of positive-ray analysis. The latter 

 method gives, in addition, the atomic weights of the 

 (wo isotopes. 



Messrs. Benn Bros., Ltd., announce for publica- 

 tion in March a work which should be of interest and 

 value to many readers, viz. "The Early Ceramic 

 Wares of China," by A. L. Hetherington, in which 

 will be described the main characteristics of the 

 products of the Chinese factories before 1368. The 

 same publishers also promise a new series entitled 

 ■ 'The Chemical Engineering Library," the first nine ! 

 volumes of which will be The General Principles of ! 

 Chemical Engineering Design ; The Layout of | 



Chemical Works, H. Griffiths; Materials of Construe- 

 tion : L, Non-Metals, H. Griffiths; Materials of Con- 

 struction: IL, Metals, H. Griffiths; Mechanical 

 Handling, A. Reid ; Weighing and Measuring 

 Chemical Products, Malan and Robinson ; Flow of 

 Liquid Chemicals in Pipes, N. Swindin; Chemical 

 Works Pumping, N. Swindin ; and Factory Wastes 

 as Fuels, A. Reid. 



Messrs. H. K. Lewis and Co., Ltd., 136 Gower 

 Street, London, have just issued an up-to-date list of 

 "College Text-books and Works of Reference in 

 Science and Technology." The titles are arranged 

 under authors' names, and are classified under 

 eighteen subjects, some of which, such as chemistry, 

 engineering, etc., are again divided. The subjects are 

 arranged alphabetically, whilst a contents-list on the 

 first pages makes reference to any subject quick and 

 easy. The list will be sent post free to any address 

 on application. 



Our Astronomical Column. 



Deduction of Star-distances from Proper 

 V Motions. — The proper motions are almost our sole 

 I guides in estimating the distances of the more remote 

 I stars. Hence any method that affords a check on the 

 !• results is of value. Prof. H. N. Russell points out 

 • in the Astrophysical Journal for September last that 

 ^ we can estimate the distance either (i) by correlating 

 the motion away from the solar apex with the sun's 

 velocity, or (2) by correlating the cross-motion with 

 the line-of-sight velocity. As a test he has divided 

 the 180 stars of type B, to Bj, the radial velocities of 

 I which were found by Campbell, into eighteen groups, 

 the mean position of each group being nearly the 

 same. He finds for the general mean parallax 

 0-0083" i^om (i) and 00058" from (2). One reason 

 given for the smaller value from method (2) is that 

 some of the stars may be undetected spectroscopic 

 binaries, in which case the adopted line-of-sight velo- 

 city is presumably too great. The probable error of 

 result (i) is oooio", of (2) 00014". In general, 

 method (i) gives the best results for objects of small 

 average velocity like the B stars, while (2) is better 

 for quick movers like the planetary nebulae. The 

 apparent close connection between period and absolute 

 magnitude in the Cepheid variables was originally 

 deduced from results obtained by method (i), and later 

 obtained considerable confirmaiion from a study of 

 the variables in the globular clusters, which appear to 

 be mainly Cepheids. 



Meteoric Shower of December 4-5, 192 1. — Mr. 

 W. F. Denning writes that he has received a com- 

 munication from the Tokyo Astronomical Observatory, 

 Japan, stating that an abundant display of meteors 

 was observed there on the morning of December 5. 

 Watching 55 minutes between 4.15 and 5.10 G.S.T. 

 of Japan (December 4 between 7.15 and 8.10 G.M.T.), 

 Mr. S. Inouye saw fifty or sixty meteors, and recorded 

 the paths of forty-six meteors, among which forty-four 

 radiated from about i56°+37° near P Leonis Minoris. 

 The meteors were rather rapid, and the magnitudes 

 ranged nearly from 20 to 4-5. 



On the next morning Mr. Inouye Watched 15 minutes, 

 but no meteors belonging to the same radiant were 

 observed. 



Mr. S. Kanda calculated the following elements from 

 NO. 2726, VOL. 109] 



the above radiant point, assuming the orbit to be 

 parabolic : 



^ = 252-1°, 10 = 232-6°, t = 133-3°, 3 = 0-791. 

 No comet is identified with these elements. 



Mr. Denning adds that this shower in Leo Minor 

 was well observed at Bristol on November 25-28, 

 1876, when he observed 26 meteors from the point 

 i55°+36°. The observation was reported in Nature 

 of December 21, 1876, p. 158. The shower was also 

 seen by him on December 2, 5, 7, and 10, 1885, when 

 the radiant point was redetermined at i52°+4o°. 



The display witnessed at Tokyo on the night fol- 

 lowing December 4 last could scarcely have been well 

 observed in England, for when the maximum occurred 

 at 7.35 p.m. G.M.T. the radiant point was close to 

 the north-north-east horizon, whereas at Tokyo it was 

 situated only a few degrees east of the zenith, and 

 splendidly placed for the abundant distribution of its 

 meteors. 



Popular Astronomy in Sweden.— The Stockholm 

 periodical Popular Astronomisk Tidskrijt continues to 

 produce articles of much interest and practical value. 

 Hafte 3 and 4, 192 1, contain a useful illustrated 

 article by Edv. Jaderin on the graphical prediction of 

 eclipses and occultations. The methods are easy to 

 follow and capable of an accuracy that is amply 

 sufficient. 



O. A. Akesson discusses the periodicity and motion 

 of sun-spots. The daily amounts of rotation for dif- 

 ferent latitudes are plotted for the two periods 1886-97 

 and 1898-1909. The values for the second period show 

 a diminution of nearly i per cent, compared with 

 the former. H. v. Zeipel contributes a study of the 

 cluster M 37, near 6 Aurigae. He finds the colour- 

 indices by comparison of photographic with photo-visual 

 magnitudes, and deduces a distance of 1500 parsecs. 

 There is also an illustrated article on the Babelsberg 

 Observatory and its new refractor (aperture 65 cm.) 

 and reflector (aperture 120 cm.), both made by Zeiss. 



The approaching series of occultations of Aldebaran 

 are the subject of a useful note. Accurate observations 

 of the bright-limb phases of these phenomena will 

 serve to test the conjecture that there may be a 

 sensible atmosphere on the moon's sunlit face. 



