Dec, 1904.1 



KNOWLEDGE & SCIENTIFIC NEWS. 



291 



ASTRONOMICAL. 



Herr Nippoldt on the Connection between 

 Solar Activity and Terrestrial Magnetism. 



In the October number of the Asliofiliysical Journal, Herr 

 A. Nippoldt, of the Potsdam Maj,'notic Observatory, criticised 

 a recent paper by Father Cortie on " The Solar Prominences 

 and Terrestrial Magnetism." The latter had endeavoured to 

 show that the eclipse spot i;rotip of i()0i, if it may so be called, 

 by far the largest spot group of the year, had no effect upon 

 terrestrial magnetism. Herr Nippoldt claims that .a sm.iU l>ut 

 e\'ident disturbance did take place duriug the pa=sage of the 

 spot. He is also emphatic that we have no right to assume 

 that no disturbance has taken place unless m.agnetic stations 

 near the pole have exhibited no deviations from their normal 

 curve. He insists that there should be no kind of statistical 

 definition of the idea of disturbance, that the maximum ampli- 

 tude can hardly be usable to decide whether or not a curve is 

 disturbed, and that we may represent the nature of the effect 

 of the solar action upon terrestrial magnelisni as a sort of 

 relay action — "the strength of the releasing solar activity need 

 not have a definite relation to the strength of the magnetic 

 storm." He therefore desires to sub.stitute for the statistical 

 method the investigation in detail, and calls for a continued 

 and uninterrupted registration of the changes occurring on 

 the sun. 



The paper is most disappointingly vague and inconclusive. 

 The small disturbance of which he gives a trace can hardly 

 be said to have been ''simultaneous " with the spot, except in 

 a very loose sense of the term, whilst it is only by a searching 

 application of the statistical method that we can hope to dis- 

 criminate between synchronisms which are purely accidental. 

 and those which may be legitimately taken as establishing 

 connection. 



* * * 



Demonstration of the Solar Origin of 

 Magnetic Disturbances. 



Quite a different method of treating this question was adopted 

 by Mr. E. W. Maunder in a paper read before the Royal 

 Astronomical Society on November 11. Tabulating all the 

 magnetic disturbances of 20' in declination and over, recorded 

 at Greenwich Observatory from 1882-1903, and computing the 

 heliographic longitude of the centre of the sun's disc for the 

 time of commencement of each disturb.ince, it became clear 

 at once that many of these disturbances recurred wlieu the 

 same solar meridian returned to the centre of the disc. lu 

 fact more than three-fourths of the total luuuber catalogued 

 (276) were included in some one of these series. There is only 

 one conclusion, it was urged by Mr. Maunder, to be drawn 

 from this relation, namely that the exciting cause of our mag- 

 netic disturbances was associated with definite limited areas 

 on the sun. Further the magnetic action, whatever its nature, 

 did not radiate equally in all directions, like light and heat, 

 but acted along verj- definite aud restricted lines. The uie.m 

 rotation period indicated for these areas was the same as that 

 given in the mean by the sunspots ; the extreme periods were 

 those given by what we may fairly call the extreme sunspots, 

 that is to say those on the equator and in latitude 30. Mr. 

 Maunder found an analogy to these magnetic streau) lines in 

 the long rays of the corona, as photograi)hed in the 1898 total 

 solar eclipse. The solar action being of this nature, it is per- 

 fectly clear that the stream lines from many spots may miss 

 our earth altogether, and hence a great spot need not neces- 

 sarily be accompanied by a magnetic storm. On the other 

 hand some of the disturbances recurred rotation after rotation 

 when the spots with which they synchronised at their 

 commencement had ceased to be visible. The paper there- 



fore not .lii. I . M: ..,:.i, an entirely new conception of the 

 solar action ni producing our magnetic disturbances, but sug- 

 gests that there are definite .ictive .ireas on the sun, intermit- 

 tent in their activity, of whieli aetivity spot formation is an 

 important phase. 



* * * 



The Spectra of R Scuti and W Cygni. 



Mr. Ralph II. ("nrtiss has succeeded iu photographing the 

 spectra of both of these stars, and found the hydrogen lines 

 bright at maximum. H Scuti gave a spectrum resembling the 

 solar type ; U' Cygni a banded spectrum, with the bands sharp 

 towards the violet and shaded off towards the rod. 



Rotation Periods of Venus and Mars. 



In till.' " Cnniptes Ki'iidus " of the I'.uis Academy, Mr. Lnwell 

 gives the result of a series of spectrographic determinations of 

 the rotation of these two planets. For Venus, the; spe(?d of 

 motion of a point on the equator was found to be practically 

 nil, the probable error of the observation only amounting to 

 o'oo.S kilometres per second, the result thus supporting the 

 idea that Venus rotates iu the same period as her revolution. 

 For Mars the speed was found as o'228, the computed value 

 being o'24i. The probalile error in the case of Mars was 

 0'0j6. The satisfactory result obtained for Mars lends sup- 

 port to that for the Larger and brighter planet. 



W'c deeplv regret to recurd the death of Mr. Frank McClean, 

 M.A., I,L.d1, F.K.S., M.Inst.C.E. Mr. McCleau was distin- 

 guished for his important tpeetroscopic researches and his 

 liberal donations to further the cause of astronomy. His 

 spectroscopic work included an ekiborate series of compara- 

 tive photographs of the high and low sun, a fine atlas in which 

 he studied the comparative photographic spectra of the sun 

 and the metals, and a great spectroscopic survey of all the 

 brighter stars in the heavens. In order to render this work 

 complete. Mr. McClean visited the Cape (observatory iu 1897, 

 where for six months he carried on his survey of the southern 

 heavens. In the course of this work, he was able to identify 

 between 40 and 50 of the lines of oxygen in the spectrum of 

 Beta Crucis. His bt'uefacf ions to astronomy include his foun- 

 dation of the Isaac Newton Studentships at Cambridge, and 

 the magnificent photographic telescope with its fine spectro- 

 scopic equipment which he presented to the Cape Observa- 

 tory. Mr. McClean died at Brussels on the morning of 

 November 8 in his sixty-seventh year. 



We heartily congratulate the Astronomer Royal, Sir 

 W. H. M. Christie, F.R.S., on his promotion to the rank of 

 Knight Commander of the Order of the Bath (K.C.B. Civil 



Division). 



* » * 



Encke's Comet. 



Enckc's Comet has been not only [iliotographed, but has 

 also been seen and observed by Professor M. Wolf at the Astro- 

 physical Observatory, Kunigstuhl, Heidelberg, on October 29. 

 It has also been observed by Professor IC. Millisevich, at the 

 Observatnry of the Roman College, in Rome, on October 30, 

 and by Professor E. Hartwig, at the Bamberg Observatory, 

 on Octolx-r 31. The Comet is nnich fainter than was antici- 

 pated, and it is feared will never be bright enough to be seen 

 with the naked eye. 



* * * 



The Parallax of Alpha. Centauri. 



At the station in the southern hemisphere of the Lick 

 Observatory, located at Santiago de Chile, observations have 

 been made during the past year of Alpha Centauri, and an 

 average difference between the radial velocities of the two 

 components is found of about 5' 17 km. This may perhaps 

 lie due to the relative orbital motion of the two components, 

 and, if so, it would indicate a parallax of 076, a combined 

 mass of the components of i'9 that of the sun; and a mean 

 distance between the two components of 3-46 X 10'' km. 

 The parallax thus indicated is almost precisely that resulting 

 from heliometer observ.ations. 



