o/ 



NA'I URE 



[September 8, 1923 



and mineralogical accessories which includes a large 

 variety of micrometers, ' * -^, refractometers, 

 spectroscopes and oth< ; iccessories neces- 



sary for routine work or lur apcciai reseai " tro- 



logy, mineralogy and crystallography. Ani' lore 



iinpoit.iiit items (Icsrrihc'i .-ire I )r. A. 1 1 iit' iiinson's 

 uiii\ci.s;il i^diuonu'liT ; the itHonling inicroincler de- 

 signed by Prof. Shand for geometrical rock analyses ; 

 the stage refractometer of Dr. F. E. Wright by means 

 of which the refractive index of a liquid may be 

 easily ascertained, with an accuracy of one or two 

 imits in the third place of decimals, on any microscope 

 fitted with a Bertrand lens and a micrometer scale in 

 the ocular ; and the tank refractometer designed by 

 Mr. A. F. Hallimond and Dr. H. H. Thomas, which 

 affords a convenient means for determining the re- 

 fractive indices of liquids in bulk and is useful for 

 expeditiously preparing standard fluids for testing the 

 refractivity of minerals. A price list accompanying 

 the catalogue shows a general reduction in the prices 

 of the apparatus listed. 



Mr. H. Ling Roth, of the Bankfield Museum, 

 Halifax, has in the press a work on " The Maori 

 Mantle," with numerous illustrations and plates. 



The Annali di Chimica is a new journal published 

 at Trieste, devoted to chemical and " astrochemical " 



matters. The second number, which we have just 



rcrrivpfl, cnntnins articles on thr - '^iriiis 



;ini| i.th'T stars, aiiii dii the tran -asi- 



metals mto gold (rtjirintci •' ahcr juurual;. 



All who weri' attract' iie sumptuous art 



books of Mr. A. 1 liorhuni nn " Hritish Birds" and 

 " British MffT""^-'' ■ will be interested to learn that 

 the same au ; artist is bringing out through 



Messrs. Longmans and Co. in the autumn . ' ' 

 work entitled "Game Birds an'l \Vil<l-fo\si 

 Britain and Ireland," with 30 plates in colour shov. .:i^ 

 58 species. The volume uill be issued in two forms, 

 one being on large paper, I n number to 



155 copies. 



Among the forthcoming books announced by the 

 Cambridge University Press are the following : 

 " Life," by Sir A. E. Shipley, which will form an 

 introduction to biology for the general student ; 

 " Physical and Chemical Science," by W. C. D. 

 Whetham ; " The Structure of the Atom," by Dr. 

 N. R. Campbell, being supplementary chapter No. 

 17 to "Modern Electrical Theory"; and a new and 

 revised edition of Prof. G. H. Hardy's " Orders of 

 Infinity : the Infinitdrcalcnl of Paul Du Bols- 

 Reymond," in the Cambridge Tracts in Mathematics 

 and Mathematical Phvsics. 



Our Astronomical Column, 



Calendar Reform. — The League of Nations, in 

 addition to the grave political problems which con- 

 front it, has found time to appoint a committee to 

 deal with the question of Calendar Reform, more 

 especially as relating to the determination of the 

 date of Easter. The principal religious bodies are 

 represented, the Church of England by Rev. T. E. R. 

 Phillips, secretary of the Royal Astronomical Society. 

 In this connexion an interesting letter, signed ' ' Astro- 

 nomicus," appeared in the Times for August 27. It 

 quoted a resolution adopted by a council representing 

 the Greek and allied churches that was held last 

 May in Constantinople. This extended to ecclesi- 

 astical purposes the use of the Gregorian calendar, 

 which had been adopted for civil purposes in Greece 

 some months previously. Thus the Gregorian 

 calendar has now finally superseded the Julian one 

 in Europe, though the process has occupied 340 

 years. 



The resolution also affirmed the willingness of the 

 churches concerned to modify the method of deter- 

 mining Easter, provided it was kept on a Sunday 

 subsequent to the first full moon after the equinox. 

 This condition would be satisfied if Easter were the 

 first Sunday after April 20 ; this is a later date than 

 most of those suggested, which have been near the 

 middle of the present range, extending from March. 

 22 to April 25. 



Stellar Positions and the Einstein Light- 

 bending. — The idea has occurred to many people that 

 the Einstein light-bending by gravitation, the existence 

 of which was confirmed at the eclipses of 1919 and 

 1922, might produce appreciable displacements in 

 the apparent position of stars if their rays passed 

 close to other stars on their way to our system. Signor 

 O. Z. Bianco, of Turin, in a note to us, quotes Bessel's 

 view that the number of dark stars may greatly 



NO. 2810, VOL. I 12] 



exceed that of the lucid ones, and infers that serious 

 displacements of the positions of the latter may 

 result. A little consideration will, however, make 11 

 plain that the number of cases where the necessary 

 conditions prevail must be extremely small, and even 

 in these cases the proper motions of the three bodies 

 concerned (lucid star, dark star, sun) would quickly 

 modify them, so that the large shift would be of ver>' 

 brief duration. 



A ray passing at a distance of one astronomical 

 unit from the sun is deflected through an angle of 

 o-oi". A study of the stellar masses shows that onl\ 

 a very small minority of the stars have masses greatly 

 in excess of the sun's. Moreover, the majority of 

 the stars are at such distances that an astronomical 

 unit subtends an angle of less than o-oi'. Even if we 

 supposed the dark stars to outnumber the lucid ones 

 a thousand-fold, there would be very few cases of 

 two independent stars approaching each other so 

 closely in direction ; but, as a matter of fact, dynamical 

 researches on the stellar motions give no support to 

 the existence of such a large preponderance of dark 

 stars. 



It may further be pointed out that shifts of the 

 order of o-ox' in the positions of stars are quite 

 unimportant, being far below the probable errors of 

 the best catalogues. As an illustration of this it 

 may be mentioned that the correction of meridian 

 observations for the Einstein shift due to the sun has 

 not been suggested by any one, though it would fre- 

 quently mount to 0-02''. It has already been mentioned 

 in these notes that the Einstein displacement has no 

 effect on the relative positions of binary stars, but 

 onlv comes into play when one orb is far behind the 

 other. The argument outlined above shows that 

 Signor Bianco's fears are groundless, and that no 

 appreciable errors in star-positions from the cause 

 mentioned are to be apprehended. 



