442 REPORT — 1882. 



6. On some Matters relating to the Sun. 

 By Dr. Arthur Schuster, F.E.S. 



Observations of tlie sliape assumed by the solar corona in successive eclipses 

 during the last fifteen years have shown remarkable changes coincident with the 

 sunspot period. The corona of sunspot minimum is characterised by a certain 

 symmetry about an axis not far removed from the sun's axis of rotation, but very 

 likely not quite coincident either with it or with an axis perpendicidar to the plane 

 of the ecliptic. Some apparent irregularities in the symmetry seem to be due to 

 differences in the position of the earth in its annual orbit. Changes in the spectro- 

 scopic and polariscopic properties of the corona which are coincident and con- 

 nected with the changes of form seem to point to a partly meteoric origin of the 

 corona. 



7. On the Method of Harmonic Analysis used in deducing the Numerical 

 Values of the Tides of long period, and on a Misprint in the Tidal 

 Eeportfor 1872. By G. H. Darwin, F.B.S.—See Reports, p. 319. 



8. On the Photographic Spectrum of Comet (Wells) 1, 1882. 

 By William Huggins, B.C.'L., LL.D., F.B.S. 

 [Plate IX.] 



Last year I had the honour of presenting to the British Association an account of 

 a photograph of the spectrum of the brightest comet of that yeai', accompanied by 

 some remarks on the unity of type of spectrum of all the comets to which the 

 spectroscope had been applied since 1864. 



The bright comet of the present year presents, for the first time, a spectrum 

 differing essentially from the hydrocarbon type to which aU the other comets 

 belonged. 



Observations of the visible region of tlie spectrum had already showed the 

 probable absence of the usual hydrocarbon groups, one or two observers suspecting 

 only the brightest of the groups. The comet gave a brilliant continuous spectrum, 

 and also a bright double line coincident witli that of sodiimi at D of the spectrum, 

 and some other bright lines. 



On May 31, I obtained a photograph of the spectrum of this comet. The plate 

 was exposed for one hour and a quarter. Through the second half of the slit I took 

 on the same plate a spectrum of a Ursa majoris for the determination ui position of 

 the lines of the comet's spectrum. 



The photographic plate showed a strong continuous spectrum extending from 

 about F to a little beyond II. 



In the continuous spectrum of the comet of last year the Fraunhofer lines were 

 clearly visible, but in the stronger continuous spectrum of the present comet, I was 

 not able to distinguish any of these solar lines. 



The slit was indeed more open than was the case last year, and this circumstance 

 would make these lines less distinct, but tlie lines G and II are weU seen in the 

 star's spectrum taken under the same conditions. We may conclude therefore that 

 the part of the comet's original light whicli gives a continuous spectrum is much 

 stronger relatively to the reflected solar light in this comet than was the ease in 

 the comet of last year, and for this reason the Fraunhofer lines are not to 

 be seen. 



In agreement with eye observations made in the visible region, this photo- 

 graph does not contain the strong ultra-violet group assigned to cyanogen ; also 

 the bright groups of the comet of last year between G and /;, and between /* and H 

 do not appear to be present. 



In the continuous spectrum at least five places of greater brightness can be dis- 

 tinguished, which undoubtedly represent groups of bright lines, though they are 

 not sufficiently distinct in the photograph to admit of resolution into lines. The 

 correctness of this interpretation is rendered much more probable by the circum- 

 stance that these groups, as is shown in the diagram, project beyond the strong con- 



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