232 



NA TURE 



[December 24, 1908 



spectrum of the comet, including some taken with a 

 calcite-quartz spectrograph, which show new radia- 

 tions and will enable better wave-length values to be 

 determined ; the conclusions published in the first note are 

 to be looked upon as only provisional. 



Observations of the Surfaces of Jupiter's Principal 

 Satellites and of Titan. — During the 1907-8 opposition 

 of Jupiter, M. J. Comas Sola continued his observations 

 of the principal Jovian satellites, and now publishes his 

 results, with drawings of J iii. and iv., in No. 4290 of 

 the Astronomische Nachrichten (p. 290, December 11). 



Satellite i. appears to be definitely ellipsoidal, the 

 flattening amounting to as much as one-fifth of the major 

 axis. The direction of the longest axis is not, according 

 to M. Sola's observations, parallel to that of Jupiter's 

 bands, but has a position-angle some 28° greater than 

 that of the bands. 



With most other observers, M. Sola finds that the 

 second satellite always appears round. 



The observations of J iii. are given in detail, and many 

 features on the satellite's surface noted, .^mong these, 

 white polar caps, varying in intensity and size from time 

 to time, equatorial bands, and shadowy areas were 

 observed, and, from the varying appearance of the latter, 

 it would appear that the effects of the satellite's rotatior 

 were seen. 



Satellite iv. presented no feature which could be seer 

 definitely, with the exception of a very faint north polai 

 cap on December 24, 1907, but several wore suspected 

 from time to time. 



The observations of Titan indicate that this member 

 of the Saturnian family has a more or less dense atmo- 

 sphere, for the limbs were always dark and difficult to 

 see, whilst towards the centre of the disc lighter patches 

 were visible. The drawing for .'\ugust 13, 1907, shows 

 two of these patches having the appearance of a very 

 difi'use double star. 



Corrections of the Position and Diameter of 

 Mercury. — From observations of the contacts during the 

 transit of Mercury on November 13-14, 1907, Prof. Stroo- 

 bant has deduced corrections for the position and diameter 

 of the planet, and publishes the results in part i., vol. xii., 

 of the Annates astronomiques de VObservatoire royal dc 

 Bclgique. 



The observations were made at thirty-three observa- 

 tories in diffrrent localities in Europe, South .Africa, and 

 the United States, and their discussion leads to the follow- 

 ing results : — Instead of the diameter being 6"-6i, at unit 

 distance, as usually accepted, it is 6"-i6, and, consequently, 

 the actual radius, taking the equatorial radius of the earth 

 as 6378 km., is 2232 km. From this it follows that, as 

 compared with that of the earth, the volume of Mercurv 

 is 0043 instead of 0052, whilst the density is 1-42 instead 

 of 117, if the accepted value for the mass be retained. 

 The corrections to the nosition of the planet in the equa- 

 torial coordinates are Aa= -|-o-ofi6s. and A5= -o"-22, and 

 in the ccliotic coordinates 4-o".97 and +o"-o^ in longitude 

 and latitude respectively. 



The South Polar Cap of Mars. — Bulletin \o. 35 of the 

 I-owell Observatory contains Prof. Lowell's liieasures, 

 made from drawings, of the size of the south polar cap 

 of Mars between March 22 and November 13, 1007. 



The tabulated results give the history of the cap for 

 about eight of our months, from about its maximum to 

 near its minimum area, and show that its size decreased 

 regularly from about 0-388 of a hemisphere to 0002. 



The " Companion to the Observatory.". — This useful 

 annual, published by Messrs. Taylor and Francis at 

 i.t. 6d., contains the usual data and ephcmerides for the 

 observations of the sun, planets, eclipses, satellites, 

 variable and double stars, &c. 



Mr. Denning has revised the meteor notes, Mr. Maw 

 has supplied a number of observations of double stars, 

 and M. BaiUaud has furnished advance proofs of the 

 Annuaire du Bureau dcs Longitudes from which the list 

 of Algol variables has been copied. 



A useful list of the standard times of various countries 

 using the Greenwich meridian is given on p. 32, and from 

 the table of the magnetic elements for Greenwich Observa- 

 NO. 204,^, VOL. 7q] 



tory we see that the " inferred " values for 1909 are : — 

 declination, 15° 50' W. ; horizontal force, 0-1854; ^'Pi 

 66° S5'- 



The Ntzamiah Observatory at Haidarabad. — The 

 establishment by his Highness the Nizam of Haidarabad 

 of a well-equipped astronomical observatory in his 

 dominions is referred to in the Times of December 17. 

 The equipment includes, besides the purely astronomical 

 and meteorological instruments, a very complete photo- 

 graphic department and extensive workshops fitted with 

 modern tools and appliances for both wood and metal 

 working. 



PRIZE SUBJECTS PROPOSED BY THE 

 FRENCH ACADEMY OF SCIENCES FOR 



THE YEAR 1910. 

 f'^ EOMETKY. — The grand prize of the mathematical 

 sciences (3000 francs). The problem of finding all 

 the systems of two raeromorphic functions in the plane 

 of a complex variable and connected by an algebraic rela- 

 tion is known. The analogous question is suggested for 

 a system of three uniform functions of two complex 

 variables, having everywhere at a finite distance the 

 character of a rational function and connected by an 

 algebraic relation. In default of a complete solution of 

 the problem, to indicate examples leading to classes of 

 new transcendental functions. The Francoeur prize (1000 

 francs), for work in pure or applied mathematics; the 

 Poncelet prize (2000 francs), for a work on pure mathe- 

 matics. 



Mechanics. — A Montyon prize (700 francs), for invent- 

 ing or improving instruments useful to the progress of 

 agriculture, the mechanical arts, or sciences ; the 

 Fourneyron prize (1000 francs), for an experimental and 

 theoretical study of the effects of shocks of a hydraulic 

 ram in elastic tubes. 



Navigation. — The extraordinary prize of 6000 francs, for 

 work tending to increase the efficiency of the French 

 naval forces ; the Plumey prize (4000 francs), for improve- 

 ments in steam engines or any other invention contributing 

 to the progress of steam navigation. 



.Astronomy. — Pierre Guzman prize (100,000 francs), for 

 the discovery of a means of communicating with any 

 planet other than Mars, or, failing this, the interest will 

 be awarded for work leading to progress in astronomy ; 

 the Lalande prize (540 francs) ; the Valz pi ize {460 francs) ; 

 the Janssen prize, for an important progress in astronomical 

 physics. 



Geography. — The Tchihatchef prize (3000 francs), for 

 .■\siatic exploration : the Binoux prize (2000 francs'), for 

 work on geography or navigation ; the Delalande- 

 Gu^rineau prize (1000 francs) ; the Gay prize (1500 francs), 

 for zoological and anthropological researches in South 

 America, especiallv in the region of the .Andes. 



Pliysics. — The Hijbert prize (1000 francs), for a discovery 

 in electricity of practical or industrial use ; the Hughes 

 prize (2500 francs) ; the Kastner-Boursault prize (2000 

 francs), for the best work on the application of electricity 

 in the arts, industry, or commerce. 



Chemistry. — The Jecker prize (10,000 francs), for work 

 in organic chemistry ; the Cahours prize (3000 francs), for 

 the encouragement of young chemists ; Montyon prizes 

 (unhealthy trades) (2500 francs and a mention of 1500 

 francs), for improving the hygienic conditions of an un- 

 healthy trade or calling ; the Berthclot prize (500 francs) ; 

 the .■\lhumbert prize (looo francs), for an experimental 

 study of the electrical properties of the metallic alloys. 



Mineralogy and Geology. — The Delesse prize (1400 

 francs). 



Botany. — The Desmazi^res prize (1600 francs), for a 

 memoir on cryptogams; the Montagne prize (1500 francs), 

 for w^ork on the anatomy, physiology, development, or 

 description of the lower cryptogams : the de Coincy orize 

 (900 francs), for a work on phanerogams : the de In Fors- 

 Melicocq prize (ooo francs), for a work dealing with the 

 botany of the north of France ; the Bordin prize (3000 

 francs), for a study of the origin, development, and dis- 

 appearance of the transitory tissues which may enter at 

 various periods into the structure of the vascular plant. 



