October 19, 1905] 



NA TURE 



611 



feature of this eclipse, and were recorded by rnany observers 

 at Sfax as being sinuous, undulating, and nearly parallel. 

 They travelled at a rate equal to the average walking pace 

 of a man {Comptes rcndiis. No. 14). 



Atmospheric Origin of " Sh.\dow Bands." — In No. 

 4049 of the Astronomische Nachrichteh Signor T. Zona, 

 of Palermo, suggests that the shadow bands observed 

 during a total eclipse of the sun are of a purely atmo- 

 spheric origin. He has observed that the rays of light 

 projected from a man-of-war's searchlight on to a w'all 

 several kilometres from the ship exhibit just the same 

 kind of light and dark bands that he observed at Sfax 

 during the recent solar eclipse. 



Similarly, he noticed that the light from Venus projected 

 through a small window on to the opposite wall of the 

 room in which he was seated exhibited the same appear- 

 ance. 



Signor Zona suggests that the atmospheric vibrations 

 which cause the agitation seen at the sun's limb, when 

 the latter is observed directly, are the cause of the 

 oscillating bands seen during total eclipses. 



A Spectrogr.aphic Determin.ition of the Sol.ar 

 P.\R.\LL.AX. — In Nos. 4048-g of the Astronomische Nach- 

 richtcn Herr F. Kiistner describes in detail a method which 

 he has employed to determine the sun's parallax spectro- 

 graphically, from measurements of sixteen lines on each 

 of eighteen spectrograms of Arcturus, obtained during the 

 period June 24, igo4-January 15, 1905, with the Bonn 

 spectrograph. From these measurements he found the 

 radial velocity of Arcturus relative to the sun to be 

 — 4-83 +0-27 km. for the epoch 1904-8, and the value for 

 the mean velocity of the earth to be 29-617 + 0057 km., 

 the accepted value for the velocity of light in vacuo being 

 299865 + 26 km. per second. 



As the solar parallax previously accepted, viz. 8"-8oo, is 

 'based on the assumption that the earth's velocity is 

 29-765 km., and as these two quantities varv proportionally, 

 it follows that with a more correct value for the latter a 

 more refined value for the former may be determined. 



Having made the determination, Herr Kiistner arrives 

 at the quantity 8"-844 + o"-oi7 as his final result for the 

 value of the solar parallax. 



Nov.^ Aquil.^ No. 2. — The results of several recent 

 observations of the Fleming Nova are published in No. 

 4049 of the Astronomische Nachrichten. 



Prof. Wolf, observing on September 17 at 8h. 4-3m. 

 (Konigstiihl M.T.), found [he Nova's magnitude to be 

 9-6, showing a decrease of not quite 0-3 mag. since 

 September 4. 



Dr. Guthnick, observing at Bothkamp, obtained the 

 photometric results shown in the following table : — 



Sept. 5 



The magnitudes are based on those given for the com- 

 parison stars in the Harvard photometric revision of the 

 B.D. catalogue. 



LiGiiT-VARHTiON OF S.1TURN 's SATELLITES. — From observ- 

 ations made on twelve evenings. Dr. P. Guthnick, of 

 Bothkamp Observatory, has determined the phases of the 

 magnitude changes of Tethys, Dione, Rhea, and Titan. 



He found that the first named is brightest when at 

 easterly elongation (90°) and faintest at about 330°. Dione 

 reaches its maximum brightness at 90° and its minimum 

 at about 40°. Rhea apparently has two maxima, one at 

 40°-i20° and a fainter one at 240°, the corresponding 

 minima occurring at 180° and 330° respectively. The 

 maximum brightness of Titan occurs at 240°, its minimum 

 brightness at 20°. In regard to Japetus, Dr. Guthnick's 

 observations confirm the results obtained by Prof. Picker- 

 ing, viz. that the maximum brightness of that satellite 

 occurs at the western, and the minimum at the eastern, 

 elongation. The range of light-variation for each of the 

 satellites Tethys, Dione, and Titan is about 0-75 mag., 

 for Rhea about i-o mag., and for Japetus about 1-75 mag. 

 (Astronomische Nachrichten, No. 4049). 



NO. 1877, VOL. 72] 



INTERNATIONAL CONGRESS ON RADIOLOGY 

 AND lONISATION. 



T^HE first international congress for the study of 

 radiology and ionisation, organised under the auspices 

 of the Belgian Government, was held at L\6ge on 

 September 12-14. The work of the congress was divided 

 into two sections, devoted respectively to physical and 

 biological science. The first section dealt with the follow- 

 ing questions : — (i) physics of electrons, comprising also 

 radiations of all kinds ; (2) radio-activity and the accom- 

 panying transformations ; (3) meteorological and astro- 

 nomical phenomena attributable to ionisation, radio-activity, 

 and to radiations of different kinds. The second section 

 had for its scope the study of the physiological properties 

 of the radiations and their application in medicine. 



The opening session of the congress was held in the 

 physics theatre of the University of Li^ge on September 12 

 under the presidency of Prof. Kuborn, member of the Royal 

 Belgian Academy of Medicine. Among the members present 

 mav be named Profs. Becquerel, Bouchard, and Bergonie, re- 

 presenting the French Republic, Senor J. Murioz del Castillo, 

 officially representing Spain, Drs. E. F. Nichols and \V. 

 Dieffenbach (United States), Prof. Hurmuzescu (Roumania), 

 Prof. Gillon (Italy), Dr. Yankorits (Servia), Lion Sy Thang 

 (China), Dr. Arrago (Guatemala), Dr. Ortiz (Argentine). 

 Prof. Lassar represented the Rontgen .Association of Berlin, 

 Prof. Onnen the Royal Society of Batavia, and Mr. Wilton 

 the University of Adelaide, .South Australia. The follow- 

 ing were also present : — Messrs. Birkeland, Himstedt 

 (Freiburg in B.), Gariel (Paris), and Legge (London). 



Sir William Ramsay had intended to present an address 

 on radio-thorium, but in his unavoidable absence it was 

 read on his behalf. M. Becquerel gave a lecture on the 

 analysis of the radiations of radio-active substances. The 

 address will be published in the Conrptes rcndiis of the 

 congress, shortly to be issued by the organising committee 

 (general offices. No. i Rue de la Prevote, Brussels). 



On September 13 a general meeting w-as held. Prof. 

 Wind, of Utrecht, presented a communication on the 

 diffraction and wave-length of the ti-rays, and demonstrated 

 the character of the apparatus designed by his colleague 

 M. Haga and himself for the study of this much contro- 

 verted question. Prof. Lassar, of Berlin, gave an account 

 of the practical application of the new radiations. M. 

 Tommasina, of Geneva, described a study of the radio- 

 activitv produced by atmospheric air (Elster and Gcitel's 

 phenomenon), and papers relating to the therapeutic action 

 of the X-rays and of radium were read by Drs. Bergonit- 

 (Bordeaux), Dieffenbach (New York), and Kassabian 

 (Philadelphia). The latter's hands, owing to their frequent 

 exposure to the radiations used for therapeutic treatment, 

 have during the past few years undergone characteristic 

 changes. 



The following papers of notew-orthy interest were pre- 

 sented at later meetings : — Remarks relative to the termin- 

 ology of ionisalirn. Prof, de Hemptinne (Louvain) ; dis- 

 ruptive discharge in gases at high pressures. Prof. Guye 

 (Geneva) ; the spectroscopic study of radium light. Prof. 

 Himstedt (Freiburg in B.) ; the kinetic theory of the 

 electron serving as a basis for the electronic theory of 

 radiation. Dr. Tommasina (Geneva) ; on the radio-active 

 constituents of sediments from Echaillon and Salins- 

 Moutiers, Dr. Blanc (Rome) ; a new apparatus for deter- 

 mining the radio-activity of spring-waters, Dr. H. Sieve- 

 king (Karlsruhe) ; Moser's radiations. Prof. Piltschikoff 

 (Kharkofl) : discharge phenomena caused by X-rays and 

 radium radiations, and the transformation of these rays. 

 Prof. Hurmuzescu ; critical observations on the theories of 

 atomic disintegration and chemicophysical dissociation. 

 Prof. Munoz del Castillo ; the method of transmission of 

 e.xcited activity to the kathode, Mr. Makower (Manchester); 

 radio-activity of the lava from Vesuvius (eruption of 1904), 

 Dr. Tommasina ; on the change of properties of the 

 chemical elements. Prof. Fabinyi (Kolozsvar, Hungary) ; 

 (i) the experimental methods of studying the transform- 

 ations of the X-rays and the secondary rays resulting there- 

 from, (2) classification and mechanism of the different 

 electric phenomena caused by the X-rays, Prof. Sagnac 

 (Paris) ; absorption phenomena of radium and polonium 



