6z6 



NATURE 



[February 4, 19 15 



and airships modern warfare has been rendered more 

 than ever dependent on the weather. 



The Central for December, 1914, states that 174 

 former students or members of the staff of the City 

 and Guilds College, Exhibition Road, South Kensing- 

 ton, are now on active service. The positions held by 

 some of these are mentioned in the nine pages devoted 

 to old students and their doings, which always forms 

 one of the most noticeable and, to most readers, wel- 

 come features of the magazine. A well-illustrated 

 article of exceptional interest is that by Mr. A. C. 

 Cookson describing the work which falls to the lot 

 of the maintenance department of a railway. 



Part I. of the new volume of the Proceedings of 

 the Physical Society of London extends to 117 pages. 

 The. president. Sir J. J. Thomson, opens the volume 

 with the account he gave at the Cambridge meeting 

 of the society of his attempts to produce radiations to 

 fill the gap of about eight octaves between the softest 

 Rontgen radiation and the shortest ultra-violet rays. 

 His address as president closes the issue. It deals 

 with the production and nature of the ions in gases. 

 At the present time the interaction between ions and 

 molecules appears to be explainable either by Max- 

 well's inverse fifth povver law or by the law of impacts 

 of hard spheres. Two papers are devoted to electrical 

 questions — Mr. D. Owen's on an alternating-current 

 bridge method of determining inductance in terms of 

 resistance and capacity; and Mr. A. F. Hallimond's 

 on the voltage ampere curves given by a great num- 

 ber of point contacts when the voltage applied to the 

 contacts is gradually raised. The only paper on heat 

 is Mr. Barratt's on the heat conductivities of a num- 

 ber of glasses, woods, and other bad conductors. Two 

 papers deal with general physics. Mr. B. W. Clack 

 gives the final results of his work on the diffusivities 

 of salts in dilute solutions, and Prof. E. P. Harrison 

 traces the effect of temperature on Young's modulus 

 for wires. 



In the Revue g^ndrale des Sciences (vol. xxv., 

 p. 777) M. Louis Brunet discusses the position of 

 the combatant nations as regards the power of ob- 

 taining supplies of the metals copper, zinc, lead, tin, 

 nickel, and mercury, which play so important a part 

 in modern warfare. The conclusion reached is that 

 the position of the Franco-Anglo-Russian alliance is 

 far better than that of the central European empires, 

 not so much on account of the greater producing 

 power of the alliance, but owing to its mastery of 

 the sea, which has enabled the English and French 

 fleets to prevent in large measure the importation of 

 metals declared "contraband of war" from neutral 

 countries into Germany and Austria. 



The Times Engineering Supplement of January 29 

 gives an interesting account of aeronautics in 1914- 

 Among other notable achievements of the past year 

 are the British record of 135 miles an hour, heights 

 of five miles scaled, or closely approached, by both 

 French and German machines, and flights in seventy 

 miles-per-hour winds by fliers who do not pretend 

 to be " star-pilots." No fewer than nineteen persons 

 NO. 2362, VOL. 94] 



flew together in one huge aeroplane of Russian make 

 in 1914. One of our own Army-built stable aero- 

 planes has climbed at the rate of 1700 ft. a minute — 

 a rate of ascent four times as fast as an express lift 

 in an American hotel. Eight months ago Dr. Glaze- 

 brook gave, before the Aeronautical Society, a risumi 

 of the experiments which had achieved stability — 

 experiments vouched for by Colonel Seely, who verified 

 them by making uncontrolled flights in person with- 

 out any previous practice. Though Bryan and Harper 

 had published their mathematical work in 1911, and 

 Lanchester three years before that, it was only these 

 telling practical outcomes of their work that brought 

 these authors into their own in England during the 

 past year. 



OUR ASTRONOMICAL COLUMN. 



Wolf-Rayet Stars and the Planetary Nebula. — 

 There are indications that these enigmatic bodies will 

 shortly be fitted into the scheme of stellar evolution. 

 Hitherto, whilst it was felt that they must be more 

 or less related, actual evidence was of the slenderest. 

 Prof. J. W. Nicholson was, however, led by his mathe- 

 matical investigations of the spectra of nehuliuni and 

 Wolf-Rayet stars to suggest that they were successive 

 stages in the evolution of matter. Perhaps we can 

 now say that this is an observed fact. The Astro- 

 physical Journal for December (19 14) contains some 

 remarkable preliminary results obtained by Mr. W. H. 

 Wright in the course of the spectroscopic examination 

 of some planetary nebulae possessing central condensa- 

 tions. A spectrogram secured with the 36-inch refractor 

 (Lick), under exceptionally close following during a 

 long exposure on N.G.C. 6572, showed the spectrum 

 of the nucleus crossed by the bright nebular lines of 

 the envelopes, and, moreover, in the spectrum of the 

 nucleus appeared a band 17 A. wide in place of the 

 line A 4686. These facts recalled the hitherto unique 

 hydrogen envelope star of Campbell (BD + 3o° 3639). 

 Detailed study of the spectrum of this body was then 

 undertaken and, as was expected, the fact was estab- 

 lished that the hydrogen envelope really gave the 

 spectrum of a planetary nebula. 



Here, then, are two cases of planetary nebulae 

 having nuclei which exhibit the spectra of Wolf-Rayet 

 stars and, together with three other cases (N.G.C. 

 6826, N.G.C. Index 418, and N.G.C. 40) cited from 

 unpublished observations by Merrill, Campbell, and 

 Paddock respectively, the facts are held to justify the 

 conclusion that such nuclei are in all cases Wolf-Rayet 

 stars. The evidence does not establish the converse 

 proposition that Wolf-Raj^et stars are in all cases the 

 nuclei of planetary nebulae The author promises a 

 more detailed account of the observations and also 

 the early publication of a list of nebular lines. The 

 materialisation of these promises will be eagerly 

 anticipated 



The Solar Rotation in 1913. — In the current num- 

 ber of the Journal of the Royal Astronomical Society 

 of Canada (September-October, 1914) Mr. H. H. 

 Plaskett gives an account of the results of a study of 

 the solar rotation which he and Mr. R. E. De Lury 

 secured during 1913. The method was spectroscopic, 

 and the region of the spectrum examined was A 5600 ; 

 thirty-one plates were utilised, on each of which were 

 recorded nine rotation spectra ; in these spectra dis- 

 placements were measured for twelve lines. Tables 

 summarise the measures and the results. The results 

 are compared with those obtained for the same region 

 of the spectrum in the years 1911 and 1912 by Messrs. 



