1865.] Prof. Phillips Notice of a Spot on the Sun. 479 



Supplementary Note, Nov. 25, 1865* 



The spot to which the above notices refer has been made the subject of 

 careful observations by M. Chacornac, who has issued interesting descrip- 

 tions and drawings of it from October 7 to October 16. The Rev. Mr. 

 Hewlett has also scrutinized the same object, and prepared drawings to 

 October 17, the day when my first sketch was made. Thus we have 

 for this spot observations through one rotation and a half, and we may 

 perhaps have the pleasure of welcoming it again in a new form. J. P. 



III. " Notice of a Spot on the Sun, observed at intervals during one 

 Rotation." By JOHN PHILLIPS, M.A., LL.D., F.R.S., Professor 

 of Geology in the University of Oxford. With Drawings. Re- 

 ceived November 15, 1865. 



On the 17th of October, 1865, at 2 P.M. the spot referred to had tra- 

 versed a great portion of its arc, and was approaching the limb. It showed 

 two large unequal umbrae, and in each of them a blacker nucleus. Between 

 them were several small dark dots, partially coalescent. The edges of the 

 umbrse were very irregular. In the smaller umbra two bright dots. 

 Above the larger umbra (which appeared to the right in the telescope) was 

 an exceptionally bright band, traversed by two dark threads ending in dark 

 dots. This band crossed a part of the umbra, like a bridge, but itself was 

 there traversed by a small bar. Four bright patches lay in the continu- 

 ation of this facula toward the prolonged upper (apparently) extremity of 

 the penumbra, which was itself more luminous than other penumbral parts. 

 The penumbra had broken edges, and an interior mottling of small brighter 

 and darker spaces directed variously toward the umbrse. The granulated 

 surface of the sun with soft gleaming facular ridges was conspicuously 

 seen, and tracts of darkly dotted surface were seen beyond each extremity 

 and on one side (PI. X. fig. 1). 



Nov. 4, 9.45. The spot had now returned by rotation, and was very 

 distinctly seen amidst far extended clouds of bright faculae, though reduced 

 to less than half its former dimensions. It retained the two umbral tracts 5 

 but it was now the left-hand tract which was the larger. Being about 15 

 from the lirnb, the general figure was oval, as usual ; the umbrae were of 

 irregular figure, the larger one cut into by bright branches from the inter- 

 umbral space. Dark dots amidst the faculae on the border (PI. X. fig. 2). 



Nov. 6, 9.45. The spot had reached about 45 from the edge, and 

 appeared less elliptical, and otherwise changed in aspect. The large um- 

 bra was much dissected by bright streams, and the smaller one had assumed 

 a distinctly tripartite shape. The edges of the penumbra appeared rugged. 

 Many small spots and dark dots towards the edge of the disk (PI. X. fig. 3) 



Nov. 11, 9.45. The spot had now passed the central meridian, and 

 was greatly altered, and almost cut into two parts by a bright facular mass, 

 passing between the umbrse. The larger of these is now in a pentagonal 



