564 



NATURE 



[June 22, 191 1 



iiickly by an electric field. In the former case satura- 

 1 on currents can be obtained, in the latter the current 

 increases indefinitely with the voltage applied. In either 

 case the conductivity of the surrounding gas increases 

 rapidly as its pressure is diminished. 



Unoer the title of " First Report of the Bird Construc- 

 tion Committee," the Aeronautical Society of Great Britain 

 has issued an attractive pamphlet, in which it is sought 

 to summarise existing knowledge of the mechanical con- 

 stants associated with the flight of birds. A special 

 feature is the tabulated list of about 460 species of bird 

 with numerical values of their wing dimensions, weights 

 of their muscles, and similar data, compiled from the 

 works of Harting, Marey, Moillard, Mullenhof, Legal and 

 Reichel, and Winter. To the ornithologist, the list of 

 Latin names with their equivalents in English, French, 

 German, Italian, Spanish, and Russian will be exceedingly 

 useful, .'\nother pamphlet dealing with natural flight is 

 Dr. Wolfgang Ritter's study of " The Flying Apparatus 



t the Blow-fly," published by the Smithsonian Institution 

 iioii)' For the first time in this connection, photography 



vas used to delineate the structure of the wings and 

 arrangement of the thoracic muscles, most of the illustra- 

 tions being stereoscopic. Other figures give kymographic 

 curves showing the movement of the wings, and serial 

 photographs of the insect in the act of flight. Natural 

 flight also figures in a pamphlet by Dr. Otto Wiener 

 entitled " V'ogelflug, Luftfahrt und Zukunft " (Leipzig : 

 Johann Ambrosius Barth, 1911, pp. 60), based on the 

 author's contributions to the Deutsche Revue. In addition, 

 however, to sailing and other flight, the article deals with 

 the influences of artificial flight in peace and war, its 

 future effects on human progress, and other considerations 

 of an equally general character. 



OUR ASTRONOMICAL COLUMN. 



The Eclipse of the Sun, April 17, 1912. — Next year's 

 eclipse of the sun, although, under the best conditions, of 

 very short duration, is arousing a great deal of interest 

 owing to the proximity of the central line. It was at first 

 suggested that a very brief totality might occur near Paris, 

 but the slight uncertainty as to the moon's semidiameter 

 makes this doubtful ; probably it will be a very large 

 annular eclipse there. According to the data of the Con- 

 iiaissance des Temps a six seconds' totality should occur 

 in Spain, but according to those of The Nautical Almanac 

 the eclipse will not become more than annular anywhere. 



In the June number of L'Astronomie M. Landerer dis- 

 cusses the conditions for Spain, and, taking the moon's 

 semidiameter as 15' 31-62'', he finds that at one or two 

 places in the peninsula an evanescent totality should occur. 

 At El Barco (Orense) the eclipse path should have a 

 diameter of 166 metres, and totality should last for 

 0-2S., so that an intending observer would have to make 

 very sure of his position. Between El Barco and Penafiel 

 (near Oporto) would probably prove a better station, the 

 computed totality at the latter place being 0-45. For 

 Castandiello, a small village in the province of Oviedo, the 

 computed magnitude is 0-9900, and the eclipse may easilv 

 prove total. All the places are shown on a map' accom- 

 panying the article, and a special article dealing with the 

 conditions for eclipse in France is promised in the next 

 number. 



The Changes on Jupiter, 1881-1909. — An important 

 monograph of i8o pages discussing the features of Jupiter 

 during the period 1881-1909 is contributed bv Dr. O. Lohse 

 to vol. xxi. of the Publikationen des Astrophysikalischen 

 Ohservatoriums zu Potsdam, No. 62. 



The observations of the various spots, bands, and other 

 surface features of the planet are discussed individuallv, 

 and the descriptions often illustrated by a sketch of the 



NO. 2173, VOL. 86] 



special feature made at the time of observation. Meri- 

 of the equatorial and polar diameters were frequently ; 

 with a filar micrometer, and are tabulated and di'scu;- 1 

 for each opposition. For the mean values Dr. Lo';-,' 

 obtains 38-343* ±0059'' for the equatorial, and 36-031' ± 

 0044'' for the polar, diameter; the ratio expressing the 

 amount of flattening is 1/16-584. 



The changes in various features and many other interest- 

 ing points are discussed, and the monograph concludes 

 with twelve excellent plates, eleven reproducing drawings 

 of the planet and the twelfth showing the normal jovio- 

 graphic longitudes of the Red Spot during the period 1879- 

 1909. 



Barnard's Comet, 1892 V.— The third return of 

 Barnard's 1892 comet is due this }'ear, and if the period 

 lies between 623 and 6-52 years, as given by two of the 

 three sets of elements prepared by M. J. Coniel, there is a 

 chance of its being rediscovered. 



To facilitate the search, M. Coniel publishes a compre- 

 hensive ephemeris in No. 4504 of the Astronomische Xach- 

 richten, which is based on the assumption of a period equal 

 to 6-37 years, and shows the places (for 1911) week by week 

 from July i to the commencement of 1912. 



The Motion of the Pole. — The provisional report of the 

 results obtained by the International Latitude Service, for 

 19 10, is published, as usual, by Prof. Th. Albrecht in 

 No. 4504 of the Astronomische Nachrichten. The figure 

 accompanying the paper shows that practically since 1906-1 

 the swing of the momentary, from the true, pole has been 

 increasing; the curve for 1910-0-1911-0 encircles the 

 previous spiral curve described since 1900-0. The x and y 

 values (extrapolated) for 1911-0 are +0002* and —0-282' 

 respectively. 



The Proper Motions of the Stars. — Several interesting 

 conclusions are deduced by Dr. Oppenheim in a paper 

 wherein he subjects to harmonic analysis the proper 

 motions of the stars between declinations -^38" and -+-65' 

 given in the Greenwich new reduction of Groombridge's 

 catalogue of circumpolar stars. He finds that the position 

 of the stars into swarms along definitely directed " high- 

 ways " is not finally established, and that their motions 

 can be accounted for analytically by assuming a relative 

 motion analogous to the geocentric paths of the minor 

 planets, but he leaves the question of an ideal central body 

 open (Astronomische Nachrichten, No. 4497). 



Stellar Parallaxes. — More stellar parallaxes are given 

 by Dr. Schlesinger in No. 4, vol. xxxiii., of The Astro- 

 physical Journal. Seven stars are considered, and of these 

 four have positive parallaxes greater than o-i". Among 

 the latter, one of special interest is the well-known star 

 Positiones Mediae 2164, otherwise designated Struvc 239S. 

 The distance separating the components is now 17", having 

 increased nearly 5" since the double was first measured by 

 Struve in 1832. Recent measures show that the pair has 

 a comparatively rapid orbital motion considering the great 

 separation and the faintness of the components. Dr. 

 Schlesinger finds the parallax to be +0-282' ±0-003', and 

 his results are so concordant, inter se and with independent 

 determinations, that he considers that there are few star? 

 the distances of which from us are known with so small 

 a probable error. 



Positions of Stars in the Huvghenian Region of the 

 Orion Nebula. — As a Bulletin of the Philosophical Society 

 (University of Virginia), vol. i.. No. 4, Mr. Ralph E. 

 Wilson publishes newly determined positions of a number 

 of stars in the Huyghenian region of the Orion nebula. 

 After reviewing the earlier work on the subject he gives 

 his measures in detail ; all the measures were referred 

 finally to Bond's No. 628, but Nos. 558, 669, and 6S5 were 

 also emploj'ed as fundamental stars. Six stars show what 

 appears to be proper motion, which in the case of Bond's 

 612 and 618 amounts to 4* or 5' a century northwards. 

 The motions of 622 and 636 can be explained by the sup- 

 position that they are physically connected with the 

 trapezium and share its motion. In the cases of Nos. 686 

 and 688, the proper motions are affected by large proper 

 motions, or Bond's positions are erroneous ; observations in 

 I ten years' time would probably settle this point. 



