November 7, 1895] 



NATURE 



15 



The first edition of " Practical Physiology of Plants" (Cam- 

 l)ridge University Press), by Mr. F, Darwin, F.R.S., and Mr. 

 E. Hamilton Acton, was published a year ago. . The work has 

 Ijeen appreciated from the outset, and so great has been the 

 demand for it that it has been out of print for a little time. A 

 second edition has, however, just been published ; but with our 

 pleasure that the merits of the book have been recc^nised, must 

 be mingled regret that the death of Mr. Acton should have 

 prevented him from seeing its success. 



The forthcoming number of the Physical Review (November- 

 December) will contain the following articles: — "Variation in 

 Electric Conductivity of Metallic Wires in Different Dielectrics," 

 hy Fernando Sanford ; "A Study of the Polarisation of the 

 Light emitted by Incandescent Solid and Liquid Surfaces " (IL), 

 by R. A. Millikan ; "On Ternary Mixtures" (IIL), by W. D. 

 Bancroft ; " On the Changes in Length produced in Iron Wires 

 by Magnetisation," by L. T. More. Among the minor contri- 

 butions will be : " The Limits of Pitch for the Human Voice," 

 Ijy W. Le Conte Stevens ; " The New Physics Laboratory at 

 Lille," by E. L. Nichols. 



The Quarterly Journal of the Geological Society (No. 204, 

 November), just published, is illustrated by twelve plates. The 

 contents of the number include a paper on the geology of Mount 

 Ruwenzori and some adjoining regions of Equatorial Africa, by 

 Mr. G. F. Scott Elliot and Dr. J. W. Gregory. Mr. A. Strahan 

 explains overthrusts of Tertiary-beds in Dorset, and Mr. G. W. 

 Lamplugh describes the " Crush-Conglomerates" of the Isle of 

 Man, while Mr. W. W. Watts writes on the petrography of 

 I lie same. The other authors and papers are : Messrs. W. Hill 

 md A. J. Jukes-Brown, on the occurrence of Radiolaria in Chalk ; 

 ind Dr. G. J. Hinde and Mr. H. Fox, on Radiolarian rocks in 

 •he Lower Culm Measures. 



The Meteorological Council have published the hourly means 

 >f the readings obtained from the self-recording instruments at 

 the five observatories under their control, for the year 1891. The 

 present volume contains the values for an additional observatory 

 — Fort William, the low-level station of the Ben Nevis Observa- 

 tory. An additional table has also been added to the series, 

 containing hourly sunshine values, and in an appendix will be 

 found the results of an hourly tabulation of the sunshine cards for 

 the ten years 1881-90, for seven stations, illustrated by coloured 

 plates. A summary of the hourly and seasonal variation of sun- 

 shine, based upon these values, was submitted to the Royal 

 Meteorological Society, by Mr. R. H. Curtis, on June 19, a 

 report of which appeared in our issue of the 27th of that month 

 (p. 215). 



In connection with the recent jubilee celebrations at the Royal 

 Agricultural College, Cirencester, which were attended by the 

 Prince of Wales, as patron of the institution, a special effort 

 \sas made to issue a number of the Agricultural Students' 

 Gazette which should be worthy of the occasion. Several past 

 l^rofessors of the college responded to the editor's call for 

 co-operation, and accordingly we find articles on " Anbury, 

 Club-root, or Finger-and-toe," by Mr. W. T. Thiselton-Dyer ; 

 a " The Rise and Progress of Veterinary Science in its Relation 

 ill Agriculture," by Prof. G. T. Brown ; and on " Meadows and 

 Pastures," by Dr. W. Fream. Old students are represented by 

 Sir Jacob Wilson, who writes on the " Progress of Agricultural 

 Education." Prof. Warington has a paper on "Organisms in 

 Soil assimilating Nitrogen from the Atmosphere " ; and amongst 

 ther subjects dealt with are the breeding of Shires, our meat 

 upply, estate fences, curd making, chlorine in rain-water, and 

 -^.unuel Hartlib and his " Legacie." 



The additions to the Zoological Society's Gardens during 

 he past week include a Macaque Monkey {Macacus cyno- 



NO. 1358, VOL. 53] 



molgus, 9 ) from India, presented by Mrs, Jackson ; three Red- 

 backed Pelicans (/V/<?fa«i/j rtifescens) from East Africa, pre- 

 sented by Mr. F. E. C. Remington ; two Verticillated Geckos 

 {Gecko verticillatus) from Burmah, presented by Mr. H. 

 Champion ; a Common Boa (Boa constrictor) from South 

 America, presented by Mr. F. J. Mitchell ; a Whimbrel 

 (Numenius phcEops), European, presented by Messrs. Mason ; 

 a Black-faced Spider Monkey {Ateles ater) from Eastern Peru, 

 a Brown Capuchin (Cebus fatuellus) from Guiana, deposited ; 

 two Black-tailed Flower-Birds {Anthornis melanura) from New 

 Zealand, two Silver Pheasants {Euplocamus nycthemerus) from 

 China, purchased; a White-tailed Gnu {Connochates ptu, i) 

 from South Africa, received in exchange. 



OUR ASTRONOMICAL COLUMN. 



Stars with Bright and Dark Hydrogen Lines. — In 

 his observations of the spectrum of the well-known bright line 

 star 7 Argus during 1893-94, Prof. Campbell noted the remark- 

 able fact that whilst the red line of hydrogen was quite bright, 

 the hydrogen lines in the violet were dark. The same peculiarity 

 was also observed in the spectrum of i\ Tauri. 



Since then Prof. Campbell has observed the spectra of all the 

 available stars showing the F line bright in their spectra, and 

 in some cases has secured successful photographs ; from a con- 

 sideration of the results obtained, he claims to have established 

 the following points. ( i ) Some stars contain both bright and 

 dark hydrogen lines. (2) The bright lines in such stars are those 

 of greater wave-length, the dark lines are those of shorter wave- 

 length. (3) The intensities of the bright lines decrease as we 

 approach the violet. (4) The intensities of the dark lines increase 

 as we go to the violet. {Astrophysical /ournal, vol. ii. No. 3, 



p. 177). 



In the case of y Cassiopeise, Prof. Campbell finds the bright 

 hydrogen lines to diminish very rapidly in intensity in the more 

 refrangible part of the spectrum, and observes that they are 

 situated within broad dark hydrogen lines ; he does not, however, 

 appear to have noticed the additional feature of the duplication 

 of the bright lines in the spectrum of this star as photographed 

 at Kensington (Nature, vol. li. p. 425), although he records a 

 similar appearance in the spectrum of <p Persei. 



As to the explanation of the somewhat strange behaviour of 

 the hydrogen lines. Prof. Campbell revives a suggestion due to 

 Prof. Frost, namely, that the selective absorption of a star's 

 atmosphere may be greater for the more refrangible rays, just as 

 the general absorption of the sun's atmosphere is greater for 

 such rays, the character of a spectrum being the resultant of 

 radiation and absorption phenomena. 



As first pointed out in connection with the meteoritic hypo- 

 theses, these stars represent a very early stage in sidereal evolu- 

 tion, and we note that Prof. Campbell adopts this view. He 

 finds also that the variations of spectrum in passing from one 

 star to another indicate that many steps in the evolutionary 

 process are represented. 



Parallaxes of Stellar Systems. — The possibility of de- 

 termining the parallax of a binary star, and hence the dimen- 

 sions and mass of the system, by a spectroscopic observation of 

 the relative velocity in the line of sight, was first pointed out by 

 Fox Talbot in 187 1, but the suggestion has not yet borne fruit. 

 Some hesitation in taking up this interesting piece of work has 

 no doubt been due to the smallness of the velocity to be 

 measured in most cases ; but now that such a high degree of 

 accuracy is attainable, there is no longer any reason to suppose 

 the method impracticable. A very simple way of computing the 

 parallax from an observed velocity in the line of sight was intro- 

 duced by Dr. Rambaut a few years ago, a knowledge of the 

 orbital elements being assumed (Monthly Notices, vol. 1. p. 302). 

 This paper seemed to supply all that was needful in the way of 

 facilitating the necessary computations ; but Dr. See has recently 

 treated the subject somewhat differently (Ast. Nach., No. 3314)- 

 The hodograph of an ellipse being a circle, the velocity at any 

 point in the ellipse is represented by the radius vector of the 

 hodograph which is parallel to the tangent to the orbit at the 

 point in question. The radius of the hodograph can be deter- 

 mined from the spectroscopically observed velocity, and the 

 value of the velocity in the line of sight can then be predicted 



