1886.] Sun-spot Spectra Observations at Kensington. 361 



It will be convenient to refer here to the facts which have been 

 recorded during those eclipses which have been observed at the 

 sun-spot minimum and maximum. 



At the minimum the corona is dim ; observations made during the 

 minimum of 1878 showed that it was only -f as bright as the corona 

 at the preceding maximum. There are no bright lines in its 

 spectrum, and both photographic and eye observations proved it to 

 consist mainly of a ring round the equator, gradually tapering towards 

 its outer edge, which some observations placed at a distance of twelve 

 diameters of the sun from the sun's centre. 



The same extension was observed in the previous minimum in 1867, 

 and the polar phenomena were observed to be identical in both 

 eclipses. At the poles there is an exquisite tracery curved in opposite 

 directions, consisting of plumes or 'panaches, which bend gently and 

 symmetrically from the axis, getting more and more inclined to it, so 

 that those in latitudes 80° to 70° start nearly at right angles to the 

 axis, and their upper portions droop gracefully, and curve over into 

 lower latitudes. 



Although indications of the existence of this ring have not been 

 recorded during eclipses which have happened at the period of 

 maximum, there was distinct evidence both in the eclipses in 1871 

 and 1875 of the existence of what I regard as the indications of out- 

 ward upper polar currents observed at minimum. 



The fact that the solar poles were closed at the maximum of 1882, 

 while they were open in 1871, is one of the arguments which may be 

 urged that at times the whole spot-zones are surmounted by streamers, 

 with their bases lying in all longitudes along the zones. 



It was probably the considerable extension of these streamers 

 earthwards, in 1882, which hid the finer special details at the poles, 

 while in 1871, the part of the sun turned towards the earth was not 

 rich in streamers of sufficient extension. 



Touching these streamers, it is an important fact to be borne in 

 mind, that no spots ever form on the poleward side of them. 



It is obvious, therefore, that spots are not produced by the 

 condensation of materials on their upper surfaces, for in that case the 

 spots would be produced in differently on either side of them, and the 

 width of the spot-zones would be inordinately increased. 



Although in the foregoing I have laid stress upon the indications 

 afforded by the observations of 1878 of the existence of a ring, it 

 should be remarked that, so far, the eclipse appearances on which the 

 idea rests have not been observed at maximum. This, however, is 

 not a fatal objection, because precautions for shielding the eye were 

 necessary even in 1878 when the corona was dim; and if it is 

 composed merely of cooled material it would not readily be photo- 

 graphed. 



