158 



NA rURE 



[Jlne iS, 1908 



The Mai'L-h number of Terrestrial Magnetism and 

 Atmospheric Electricity contains an article by Dr. L. A. 

 Bauer on the question of the exact nature of the action of 

 the earth on a magnet, which, according to our present 

 ideas, should reduce to a couple. Most careful and 

 accurate weighings of a magnet with its a.xis pointing 

 in various directions have been made on a balance specially 

 constructed to be free from magnetic material, and show 

 that on the average for stations in Alaska, British 

 Columbia, Kansas, Maryland, and Washington, the weight 

 when the south pole of the magnet was to the north 

 exceeds that when the magnet is reversed by i part in 

 1,000,000. In disturbed regions the differences of weight 

 observed exceeded i part in 100,000. Preliminary experi- 

 ments on the influence of magnetisation on the weight of 

 a magnetisable material show an increase of the order of 

 I part in 1,000,000 on magnetisation. 



The Transactions of the English Ceramic Society for 

 the session 1906-7 show that a great deal of active experi- 

 mental work is being done by members of the society, and 

 that very considerable progress is being made, with the 

 aid of scientific method, in elucidating obscure points in 

 pottery work. A number of useful investigations are de- 

 scribed in the Transactions, of which a few may be referred 

 to as possessing more than a purely technical interest. 

 Mr. Page contributes a paper on the properties of refrac- 

 tory clays, dealing principallv with the connection between 

 chemical composition and fusibility ; Dr. J. W. Mellor and 

 Mr. F. J. Austin have examined the changes in the micro- 

 scopic character of various types of refractory substances 

 when subjected to prolonged heating; and Dr. Mellor deals 

 at length with the behaviour of pyritiferous clays on 

 weathering and when heated. The members of the society 

 are to be congratulated on the work they are doing in 

 extending our knowledge of a very difficult subject. 



An eighth edition of " A Treatise on Qualitative .Analysis 

 and Practical Chemistry adapted for Use in the Labora- 

 tories of Colleges and Schools," by Dr. Frank Clowes, has 

 ■been published by Messrs. J. and A. Churchill. The pre- 

 sent edition has undergone revision mainly in the section 

 on the preparation and detection of gases, and in sections 

 dealing with the reactions and detection of organic 

 substances. 



In Prof. D'Arcy Thompson's paper " On the Shapes 

 of Eggs " in Nature of June 4, the formula on p. 113 



T T' 



should be /« + — 4- — = P, and in paragraph 13 the words 

 r r 



" the egg is invariably spherical " should be " the yolk is 



invariably spherical." The first word on the penultimate 



line of this paragraph should also be yolk and not egg. 



OUR ASTRONOMICAL COLUMN. 



Enxke's Comet, igo86. — According to the ephemeris 

 given by M. Kamensky in No. 4241 of the Astronomische 

 Nachrichten, the southerly declination of Encke's comet 

 is increasing, and the comet is apparently travelling rapidly 

 through the southern constellations Sculptor and Grus 

 towards Indus. Its position on June 21 will be' 



R.A. = 24h. om., dec. = 



-41- 



From an announcement in No. 4252 of the same journal 

 (p. 71, June 3) we learn that the position determined by 

 Mr. Woodgate, at the time of re-discovery on May 27, 

 gave corrections of -hsm. 22s. and —33' to the ephemeris. 



A Fourth Minor Planet near Juptter. — Elements 

 calculated by Dr. Ebell for the orbit of the minor planet 



NO. 2016, VOL. 78] 



190SC.S. indicate that this object belongs to the Achilles 

 group of asteroids, which travel in orbits near to that of 

 Jupiter. This malces the fourth member of this group to 

 be discovered (the Observatory, June, p. 257, No. 397). 



Observations of Jupiter's Eighth .Satellite. — A note 

 by Prof. E. C. Pickering, published in No. 4253 of the 

 Astroiioniische. Nachrichten (p. 87, June 5), states that, 

 according to a telegram from Prof. Campbell, the eighth 

 satellite of Jupiter was observed by Prof. Perrine, at the 

 Lick Observatory, on April i and 29. The last observation 

 at Greenwich was made on .April 24, so that Prof. Perrine 's 

 second observation will serve to extend the path already 

 observed, and will pro\'ide a useful check on the ephemeris 

 calculated from the results of the Greenwich observations. 



Photographic Determination of Star Colours. — In 

 No. 3, vol. xxvii., of the Astrophysical journal (.April, 

 p. i6g) there is an interesting paper by Messrs. Parkhurst 

 and Jordan, of the A'erkes Observatory, on the photo- 

 graphic determination of star colours and their relation to 

 spectral types. The method employed is based on that 

 suggested by Schwarzschild, in which it is assumed that 

 a satisfactory measure of a star's colour may be obtained 

 by comparing the visual magnitude of the star with the 

 magnitude derived from photographs taken on ordinary 

 plates, but the present workers have modified it by deter- 

 mining the " visual " magnitudes by photographic means. 

 With this object in view, they regularly exposed pairs of 

 ordinary (" Seed ") and " Pan-iso " plates, the latter 

 giving the " visual " magnitude. Their results show that 

 this method furnishes a simultaneous comparison of the 

 visual and photographic magnitudes of a star freed from 

 most of the uncertainties of ordinary visual methods. .As 

 the colour intensities thus derived correspond, in general, 

 to definite spectral types, this procedure furnishes a method 

 of determining the spectra of stars which are too faint 

 for the ordinary spectrographic method. 



The Maximum of Mira in October, 1907. — During the 

 period July 13, 1907, to March 9, 1908, Prof. A. A. 

 Nijland made a series of observations of the magnitude of 

 Mira, and in No. 4253 of the Astronomische Nachrichten 

 (p. 79, June 5) he publishes the results obtained. These 

 show that the maximum (mag. 3-25) was attained on 

 October 30, i907 = J.D. 2417879. The four last maxima 

 observed are compared, as regards their dates, with the 

 ephemeris published by Dr. Guthnick, and the differences 

 (O-C) are thus shown to be +2, —19, —13, and —16 days 

 respectively. The magnitudes at maximum range from 

 3'9 (J.D. 2417214) to 20 (J.D. 24x7552), and the periods 

 between the four most recently observed maxima, are 

 shown to have been 310, 338, and 327 days respectively. 



Determin.ation of Longitude Difference. — Bulletin 

 No. 130 from the Lick Observatory describes the recent 

 determination of the difference of longitude between the 

 Lick and Mare Island Observatories, carried out by Messrs. 

 Tucker and .Sanford during April. The difference deter- 

 mined was 2m. 30-74S., with a probable error of +o-ois., 

 and, accepting that of the Lick Observatory as 

 8h. 6m. 34-8 IS. W., this gives the longitude of the Mare 

 Island Naval Observatory as 8h. 9m. 5-555. W. 



Coronal Streamers. — In No. 4, vol. xxvii., of the 

 Astrophysical Journal (p. 286, May), Prof. J. .A. Miller 

 describes a method whereby it becomes possible to deter- 

 mine the heliocentric position of a certain class of coronal 

 streamers. The streamers discussed are those which first 

 curve away from, and then towards, the projection of the 

 pole of the sun, or vice versd. Applying his method to 

 the discussion of such a streamer, shown on the photo- 

 graphs taken by Prof. Cogshall and himself in Spain in 

 1905, he finds the latitude and longitude of the point from 

 which the streamer matter was projected, and also shows 

 that the force of repulsion is so nearly equal to the attrac- 

 tion of the sun (the ratio being as 099 : i-o) that the 

 particle considered had probably been ejected some 251,860 

 seconds — or about seventy hours — before the eclipse 

 occurred. At the time of the eclipse this particle was at 

 the point of the streamer, where it reversed its direction 

 of curvature, and was about 1-3 radii of the sun from its 

 centre. 



