132 



Dr. W. Huggins. 



expect to see the coronal matter in all cases moving exactly towards 

 or from a planet, because this matter would be also under the influ- 

 ence of a motion in the direction of its primary repulsion, and also 

 of one of rotation about the sun* 



There has been some difference of opinion as to whether the corona 

 is uniform in constitution from the sun's limb outwards, or whether 

 it consists of two parts, which have been distinguished by the names, 

 " inner corona " and " outer corona." 



There can be no doubt that at certain times, and in certain solar 

 latitudes, a lower part of the corona, such as that described by Pro- 

 fessor Langley, extending from about 5' to 10', is so much brighter 

 than the parts outside of it that it seems to form what may be called 

 an inner corona. At the same time, the photographs of different 

 ellipses, and Mr. Wesley's drawings from some of them, show dis- 

 tinctly that all the stronger indications of structure can be traced down 

 almost to the sun's limb, and that the brighter parts within some 

 6' to 10' of the limb, are not equally bright all round the sun. This 

 brighter inner part is represented very strongly in several drawings 

 which accompany Mr. Stone's paper on the eclipse of 1874, especially 

 in one by Mr. Wright.j There seems great probability that the corona 



# General Tennant, F.R.S., informs me that since this lecture was read, he has 

 calculated the places of Mercury, Venus, and Mars for the eclipse of 1871 and the 

 eclipse of 1882. He says : — 



" The positions at the eclipse of 1871 are — 



Mercury position angle 100° 39* 



Venus „ 278° 40' 



Mars „ 80° 40' 



Mercury is thus not far from the direction of the great prominences lettered H and 

 I (see catalogue at page 27 of my report, ' Mem. R. Ast. Soc.,' vol. xlii) , and corre- 

 sponds to the greatest extension of the coronal matter, namely, 45' in my table. 

 Venus is near the group lettered V, W, and X, of which group V is less only to H 

 and I in height, and corresponds to the next greatest extension of the corona 

 namely, 34' 56" in my table. The real heights of the visible extensions, allowing 

 for the foreshortening, would be for Mercury, 41' 3" or 45' 31", according to the 

 reading taken ; and for Yenus, 47' 05". Any such calculation, however, implies a 

 form of the coronal extension which does not exist. The more foreshortened ray 

 would, in fact, on account of its breadth, seem longer in proportion than the one 

 which is seen more nearly perpendicularly to its axial direction ; and in this case 

 this consideration would tend to reduce the real extension of the Yenus ray. Mars 

 does not seem to have any marked ray directed to him, but any such ray would be 

 much foreshortened if it existed. 



" At the time of the eclipse of May 16, 1882 ('Phil. Trans.,' vol. clxxv, Plate 13), 

 we should have the effects of the planets Mercury and Yenus coincident, and not 

 much foreshortened, in the coronal pictures. The combined effects of these planets 

 are shown in the protruding angle at the upper left side of the engraved corona. 

 There seems a marked protrusion of the general light thereabouts which would be 

 opposite to the planets." — August 15, 1885. 

 f " Mem. Eoy. Astron. Soc," vol. xlii, pp. 43, 51, and 53. 



