576 



NA TURE 



[October 5, 1905 



present author, this should cause the influence of the 

 collisions to disappear, so that the results should coincide 

 with those already referred to where the collisions were 

 disregarded from the outset. Nevertheless, the results of 

 the two calculations differ by lo per cent., that of Mr. 

 Godfrey giving a narrower spectrum line than the other. 



The difference of lo per cent, is not of much importance 

 in itself, but a discrepancy of this kind involves a subject 

 in a cloud of doubt, which it is desirable, if possible, to 

 dissipate. Mr. Godfrey himself characterises the dis- 

 crepancy as paradoxical, and advances some considerations 

 towards the elucidation of it. The present author has a 

 strong feeling, which he thinks he expressed at the time, 

 that \he lo per cent, correction is inadmissible, and that 

 there should be no ambiguity or discontinuity in passing 

 to the limit of free paths infinitely long. In connection 

 with some other work he has recently resumed the con- 

 sideration of the question, and he is disposed to think that 

 Mr. Godfrey's calculation involves an error respecting the 

 way in which the various free paths are averaged, h. dis- 

 cussion of the subject is given in this paper. 



Paris. 

 Academy of Sciences, September 25. — M. Trjost in the 

 chair. — On the orii^in of the principle of virtual displace- 

 ments : I'. Duhem. Descartes proposed to found his 

 system of statics on the proposition " It requires the same 

 power (puissance') to raise a given weight a fixed height 

 as to raise a weight K times as great to a height K times 

 less." M. Duhem has found that this principle was first 

 implicitly used by Jordanus de Xemore, in his Tractaltts 

 de ponderibus, dating from the thirteenth century, and 

 traces its use bv various writers down to the time of 

 Descartes in 1637. — Observation of the total eclipse of the 

 sun of August 30, made at Robertville, Algeria : M. Salet. 

 The plan of work included (i) a search for the existence 

 of a magnetic field in the neighbourhood of the sun by 

 the observation of the deviation of the plane of polarisation 

 of the coronal light ; (2) the photographic study of the 

 distribution of the polarised light of the corona ; (3) the 

 study of the atmospheric polarisation ; (4) the spectro- 

 polarisation of the corona ; and (5) the photography of the 

 ultra-violet spectrum of the corona. A risumi of the 

 results, which were successful, is given. — On the observ- 

 ations of the total eclipse of the sun of August 30 

 made at Guelma bv the commission from the Observatory 

 of Algiers : Ch. Trepied. The results obtained include the 

 confirmation of the supposed relationship between coronal 

 structure and the state of solar activity, the photo- 

 graphic impression of the moon's disc on the corona 

 apart from totality, the photographic registration of a 

 very curious phenomenon of elliptical rings, and a 

 negative exposed during the whole of totality per- 

 mitting of the study of the greatest photographic 

 extension of the corona during this eclipse and of con- 

 tributing to the elucidation of the question of the intra- 

 Mercurial planets. — New researches on the reproductive 

 apparatus of the Mucorinea; : J. Dauphin. The formation 

 of the mycelium has been followed with the microscope, 

 day by day, up to the production of the reproductive organs. 

 The effect of varying the nature of the carbohydrate present 

 in the culture medium was studied, and observations made 

 w-ith raffinose, dextrin, starch, dulcite, erythrite, glycerin, 

 ordinary alcohol, salicin, and quercite. — On the sensibilily 

 of the chlorophyll apparatus in ombrophobe and ombrophile 

 plants : W. Lubimenko. The facts observed show clearly 

 that the assimilating energy depends on the concentration 

 of the pigment in the chlorophyll grains. The curve repre- 

 senting the assimilating energy may, according to the con- 

 centration of the pigment, rise to the upper limit of the 

 natural radiation, as in ombrophobe plants, decrease 

 before this limit, as in ombrophile plants, or may remain 

 stationary, starting from a certain intensity, as in the 

 yellow leaves of Taxus. — Spontaneous vegetation and the 

 wholesomeness of drinking water : L. A. Fabre. 



GOTTINGEN. 



Royal Society of Sciences.— The Nachricliten (physico- 

 mathematical section), part iii. for 1905, contains the 

 following memoirs communicated to the society : — 



February 25.— A. Sommerfeld : The electron theory, 

 NO. 1875, VOL. 72] 



iii. ; on electrons with velocities equal to or greater than 

 the velocity of light. H. Happel ; On the equation of con- 

 dition of monatomic substances. 



May 20. — W. Holtx : How rotation can begin in .1 

 planetary nebula. W. Holtz : The reason for the star- 

 shaped appearance of the stars. C. Rung:e : On the 

 numerical solution of total differential equations. 



June 3. — H. Gerdien : \ new apparatus for the measure- 

 ment of the electrical conductivity of the air. H. Gerdien : 

 Measurements of the density of the vertical electrical con- 

 ductive current in free air during the balloon ascent of 

 May II, 1905. 



June 24. — Wilhelm Blitz : Contributions to the theory 

 of " lakes " in dyeing. 



The Business Notices, part i. for 1905, contains a report 

 on the Samoa Observatory, a long obituary notice of 

 Ernst Abbe by Prof. V'oigt, and an appreciation of Georg 

 Meissner by Prof. Max Verworn. 



New South Wales. 

 Royal Society, August 2. — Mr. H. A. Lenehan, president, 

 in the chair. — The refractive indices, with other data, of 

 the oils of iiS species of Eucalyptus: H. G. Smith. In 

 this paper the author records the refractive index, the 

 specific gravity, the specific refractive energy, and the 

 solubility in alcohol of the oil of each species. The 

 material was distilled at the Technological Museum, 

 Sydney, and most of it had been prepared for the work 

 ■■ Research on the Eucalypts and their Essential Oils," 

 by Mr. R. T. Baker and himself. The oils of those species 

 which have been obtained since that work was published 

 are also included. 



CONTENTS. PAGE 



Modern Geologists and the "Old Masters." By 



JEM 553 



Physical Chemistry. By H. M. D 555 



Stokes's Mathematical and Physical Papers. By 



H. L 555 



Our Book Shelf :— 



Garry ; '* Notes on the Drawings for Sowerby's 



' English Botany.' "— B. D. J 556 



Wells: "A Text-book of Chemical Arithmetic." — 



A. S 556 



Byrom : " The Physics and Chemistry of Mining " . 557 

 Letters to the Editor : — 



On the Absorption Spectrum of Benzene in the Ultra- 

 violet Region.— Prof. W. N. Hartley, F.R.S. . 557 



Rhymes on the Value of X. — F.R.S 558 



The Celtic Pony.— Dr. Francis H. A. Marshall . 55S 

 Greek Archaeology. (Illustrated.) By H. R. Hall . 55S 

 South African Meeting of the British Association . 500 

 Two Reports of the French Glacier Commission. 



By E. J. G 561 



International Meteorological Conference at 



Innsbruck 562 



International Union for Cooperation in Solar Re- 

 search 563 



Notes. (Illustrated.) 563 



Our Astronomical Column : — 



Further Results obtained by the French Eclipse 



Expeditions 567 



Elements of Comet 1S86 VIII 567 



The Figure of the Sun 567 



Bibliography of Halley .... • 567 



Observations of Jupiter's Satellites 567 



A Lost Double Star 567 



Type-writing by Telegraph. (Illustrated.) By 



Maurice Solomon .... 56S 



The Percy Sladen Expedition in H.M.S. Seaiark. 

 The Chagos Archipelago. {Illustrated.) By J. 



Stanley Gardiner 571 



Iron and Steel Institute 572 



Electrons and Matter 574 



University and Educational Intelligence 574 



Societies and Academies 575 



