824 



NATURE 



[June 24, 192: 



The following officers and members of council of 

 the Rontgen Society have been elected for the session 

 1922-1923 : President : Sir Humphry Rolleston ; 

 Vice-Presidents : Sir ^V. H. Bragg, Sir Ernest Ruther- 

 ford, and Dr. A. E. Barclay ; Hon. Treasurer : Mr. 

 Pearce ; Hon. Secretaries: Dr. E. A. Owen and Mr. 

 R. J. Reynolds ; Hon. Editor : Dr. G. W. C. Kaye ; 

 Council : Mr. C. Andrews, Dr. G. B. Batten, Mr. A. 



E. Dean, Mr. K. Edgcumbe, Mr. N. S. Finzi, Dr. 



F. L. Hopwood, Dr. F. H. Johnson, Mr. C. E. S. 

 Phillips, Prof. A. W. Porter, Prof. A. O. Rankine, 

 Sir Archibald D. Reid, and Dr. R. W. A. Salmond. 



Referring to a paragraph in Nature of June lo, 

 p. 755, Dr. ]\Iarie C. Stopes writes : — " May I correct 

 the impression your paragraph creates that the Clinic 

 and the Birth Control Neivs are activities of the 

 Malthusian League, as this is not the* case ? The 

 Society for Constructive Birth Control and Racial 

 Progress, with which the clinic and news are associated. 



is a distinct society with a different basis. The 

 policy of the Clinic and the Birth Control News is that 

 of constructive and scientific control, as distinct from 

 what is commonly understood as Malthusianism." 



We have received from Messrs. C. F. Elwell, Ltd. 

 (Craven House, Kingsway) a handsomely produced 

 catalogue relating to apparatus for wireless com- 

 munication. A readable introduction deals with the 

 immensity of the field of wireless telegraphy and the 

 superiority of the continuous wave over the spark 

 system of transmission. The most interesting portion 

 is that dealing with the Elwell arc equipment on the 

 Poulsen system, such as the company has supplied 

 to several well-known long-distance stations, includ- 

 ing Horsea, Eiffel Tower, Lyons, Rome, and the 

 initial station of the Imperial Chain at Leafield. 

 This apparatus is listed up to 700 amp. in the arc. 

 Interesting details are also given of steel and wooden 

 lattice aerial towers, ship receiving sets, and various 

 accessories. 



Our Astronomical Column. 



The Meteors of Pons-Winnecke's Comet. — Mr. 

 W. F. Denning writes that he regards it as highly 

 probable there may occur a meteoric shower on about 

 June 28. It will be a return of the display which 

 he witnessed on June 28, 1916. If the meteors of 

 this stream are connected with the comet of Pons- 

 Winnecke, they will have a period approximating six 

 years, and as the particles appear to be distributed 

 abundantly along a lengthy section of the orbit, a 

 repetition of the phenomenon of 191 6 may be ex- 

 pected. It is true that the cometary meteors were 

 not seen at many stations last year, although the 

 conditions appeared promising, but in Japan a con- 

 siderable number seem to have been recorded. In 

 any event it is desirable carefully to watch the 

 heavens, at the end of June, for further evidence of 

 this interesting display. There will be no moonlrght, 

 and the radiant point in Quadrans or Draco will be 

 favourably placed in the earlier hours of the night. 



The Search for new Stars. — The period of the 

 year is now approaching when the Milky Way will be 

 very favourably placed for observation in northern 

 latitudes, especially towards the end of June, and in 

 July. The constellations Cygnus, Aquila, Ophiuchus, 

 and Scorpio have been fruitful in Novae in past years, 

 and they offer the prospect of further discoveries. 

 When the moon is not bright the sky in the regions 

 indicated should be scanned carefully for new objects. 

 The best time to conduct the work will be near 

 midnight, when the summer twilight will not seriously 

 interfere. 



An observer who is not familiar with a large number 

 of the naked-eye stars, should compare the heavens 

 with a star atlas, and this method, often repeated, 

 will soon enable him to dispense with the atlas. 

 Certain new stars are very quick in their rise to 

 brilliancy, and a vast difference in their magnitude 

 often occurs in a few hours, so that it is really essential 

 to repeat the search several times in the course of 

 a night. Wherever the galaxy runs the observer's 

 eyes should diligently pursue the quest, and other 

 quarters of the sky should occasionally receive 

 attention. 



Though twelve new stars visible to the naked eye 



NO. 2747, VOL. 109] 



burst into view between 1848 and 192 1, not one 

 appears to have been recognised during the previous 

 158 years ; but this was probably due, not so much 

 to the dearth of such objects, as to the want of capable 

 observers. 



Colours of Binary Stars. — The giant and dwarf 

 theory of star-development gave a solution to an 

 astronomical enigma of long standing. This was the 

 frequency with which the fainter component of a 

 binary tends to blue, while the brighter component 

 is red or orange. On the old view this implied that 

 the component was of earlier type than the bright 

 star, and hence had developed more slowly. Some 

 suggested, as a way of escape, that the blue of these 

 stars might possibly not correspond with that 

 associated with spectral type A or B. It was, how- 

 ever, found possible to obtain spectrograms of some 

 of these blue components, which did not indicate 

 that they differed from other blue stars. As soon as 

 the giant and dwarf theory was mooted, it became 

 clear that for giant stars the blue stage was in fact 

 later than the red or yellow one. 



Mr. Peter Doig examines the question from this 

 point of view in Mon. Not. R.A.S. of April, and 

 finds that it gives much the same line of demarcation 

 between the giant and dwarf binaries as that given 

 by the absolute magnitudes, based on all available 

 parallaxes, including the spectroscopic ones. He 

 gives 33 pairs in which the stars are giants, and 

 75 in which both are dwarfs. The former list includes 

 Polaris, Regulus, Antares, (3 Cygni, f Bootis, etc. ; 

 the latter includes Castor and a Centauri. Mr. Doig 

 notes that in some cases of great difference of mass 

 the companion might have become a dwarf of a redder 

 type than the primary, while the latter was still a 

 giant. Lie then ventures to extend the principle 

 to give estimated parallaxes for some systems not 

 on the list. For example, a Librae is given as a 

 dwarf, with parallax 0-045" '< ^^^ parallax of Praesepe 

 is estimated as o-oio". The paper makes an appeal 

 for the substitution of other terms for " early " and 

 " late " as applied to spectral types, which are 

 misleading in the case of giants. Prof. Turner 

 suggested the terms " hotter " and " cooler " as 

 preferable. 



