§54 



NA TURE 



[December 23, 1922 



and Co., " Light and Colour," a book intended for 

 the general public, and dealing in a popular way 

 with the discovery of the spectrum, the nature of 

 light, the Einstein deflection of light, the quantum, 

 invisible rays, spectroscopy and the constitution of 

 the atom, the primary colours, colour blindness, 

 colour photography, artificial illumination, photo- 

 chemistry, phototherapy, and the psychology of colour. 

 Another book in the same publishers' announcement 

 list is '• Gas Manufacture, " by Dr. W. B. Davidson, 

 in which the subjects of gas engineering and gas 

 supply are fully dealt with from the chemical stand- 

 point. The book aims at meeting the demand of the 

 meer for a more intimate acquaintance with 

 the chemistry and physical chemistry of gases than 

 he may already possess, and is intended as a text- 

 book for the young student of gas engineering. 



The first part of Messrs. Wheldon and Wesley's 

 illustrated catalogue of recent purchases of rare 



books now offered for sale, which is issued this month, 

 is remarkable for the number of rare and interesting 

 books on herbal and garden literature which it con- 

 tains. There are also books on early medicine, 

 birds, shells, and other subjects, which are, in many 

 cases, fully illustrated. The transcription of the 

 titles has been very carefully done and the biblio- 

 graphic details will be of value to lovers of books. 

 The collection contains a first edition of Peregrinus 

 " De Magnete " published in 1558 and also the first 

 English edition of Harvey's account of his discovery 

 of the circulation of the blood, with the title " Ana- 

 tomical exercises concerning the motion of the heart 

 and blood." In addition, the collection contains 

 first editions of Jenner's accounts of his discovery 

 of vaccination, in regard to which it is said that he 

 was advised not to publish them in the Philosophical 

 Transactions lest they should injure his reputation 

 as author of a paper, already published therein, 

 on the cuckoo. 



Our Astronomical Column. 



Relativity and Space. — The Irish Ecclesiastical 

 Record of November 22 contains an article 011 tin- 

 subject by Rev. 11. V. Gill, S.J. It is intended foi 

 general readers, and opens with an explanation of 

 the reasons for the introduction of time as .1 fourth 

 dimension. From this the author goes on to consider 

 the nature of space, and comments on the difficulty of 

 conceiving that a mere vacuum can be modified by 

 adjacent matter, and also how matter could exert 

 its influence over remote matter across a vacuum 

 without involving "action at a distance" which 

 Einstein rejects. He then quotes Einstein's " Side- 

 lights on Relativity," an English translation of two 

 lectures delivered in 1920 and 1921. Many of 

 Einstein's followers in England have been inclined 

 to abandon the conception of the aether, but he 

 himself states " according to the general theory 

 of relativity, space is endowed with physical qualities; 

 in this sense, therefore, there exists an ether . . . 

 space without ether is unthinkable . . . there 

 would be no propagation of light. . . . But it may 

 not be thought of as . . . consisting of parts which may 

 be tracked through time." It is useful to direct 

 attention to this clear statement of Einstein's view, 

 and it would help matters if those who reject the 

 ffither conception were to indicate how they sur- 

 mount the difficulties that are pointed out. 



The Mass and Proper Motion of 40 Eridani. — 

 This interesting triple system was discovered by 

 SirW. Herschel in 1783. A is of magnitude 4=;, P. o- ;. 

 C io-8. The distance AB is 83" and BC is 3". All 

 three have the great proper motion of 4" per annum 

 in position - angle 213 . Prof. G. Abetti makes a 

 study of the system in vol. 30 of the Proceedings 

 of the Academia dei Lincei. He adopts the parallax 

 o"-2l9, which makes the absolute magnitudes 6-2, 

 11 1, 12-5. Using Doolittle's elements, which give 

 a period 180 years to BC, the masses in terms of the 

 Sun are found to be B =0-20, C =0-12. C is the least 

 massive star yet measured ; this position was 

 previously held by the companion of Krtiger 60, 

 mass 0-19. B is a very anomalous star, since it 

 appears to be of spectral type A in spite of its small 



no. 2773, VOL. no] 



luminosity ; recent photographs at the Lick Ob- 

 servatory indicate that C is of type Md. with the Hp 

 line bright. 



II ie velocity of the system at right angles to the 

 line of sight is 88 km. /sec. 



It is of interest to compare this system with a 

 Corona?, also investigated by Prof. Abetti. The 

 combined mass is here 5-57 times that of the Sun. 

 The evidence as to relative masses is contradictory ; 

 he provisionally assigns equal masses, and deduces 

 for the densities 0-34 and 0-99 in terms of the Sun. 

 The spectral types of both are F9. 



Distribution of Stars of same Spectral Class. 

 — The study of the distribution of stars of similar 

 spectra is very important, especially if it leads to 

 some definite law regarding their grouping with 

 regard to the Galaxy. The special case of the B- 

 type stars is discussed in a recent circular (No. 239) 

 of the Harvard College Observatory, by Dr. H. 

 Shapley and Miss A. J. Cannon. It was thought at 

 first that very few B-tvpe stars, fainter than the 

 seventh magnitude, existed, and that these formed 

 quite a local system. The authors find that, while 

 the former does not now hold good, the bright B 

 stars do indicate the existence of a local star cloud. 

 The results of the discussion are plotted in four 

 figures showing the galactic distribution of the stars, 

 the figures being confined to stars brighter than 

 5-26 magnitude, stars between magnitudes 5-26 and 

 6-25, between magnitudes 6-26 and 7-25, and finally 

 between magnitudes 7-25 and S25. The result of 

 the investigation clearly shows that the fainter the 

 B stars are the more they are situated along the 

 galactic equator. Quite a considerable number of 

 stars are used for each figure, namely 346, 367, 564, 

 and 719. Forming median galactic latitudes for 

 each thirty degrees of longitude the highest values 

 in each figure are - l5°-5, - i5°-o, -n°-5, and 

 ~3°-5. More than 90 per cent, of the fainter B 

 stars are within ten degrees of the galactic equator. 

 A table is given showing all known B stars to the 

 apparent magnitude 8-25 which are in higher galactic 

 latitude than 50 . 



