1866.] Prof. Phillips on a Zone of Spots on the Sun. 



63 



II. "Notice of a Zone of Spots on the Sun." By John Phillips, 

 M.A., LL.D., r.R.S., Professor of Geology in the University 

 of Oxford. Received March 22, 1866. 



During the latter half of February and the first half of March, spots of 

 extremely varied character have appeared on the sun, and have been seen 

 with great distinctness, in good observing weather, through the whole or 

 parts of two semi-rotations. On the 13th of February, at 10*^ 25"', four 

 spots were visible on the disk, in the situations marked Z, A, B, C in the dia- 

 gram No. I. In that diagram the apparent course of the sun's equator is 



Diagram No. 1. 



marked by the curved line e, and the pole of rotation at P. Thus the four 

 spots indicated for observation being all on the same side of the sun's 

 equator, and all within the latitude of 10°, constitute a zone of spots. 

 Since that date a fifth spot, D, still in the same zone, has appeared, fol- 

 lowing C. Of these Z was about to disappear ; its reappearance was 

 noted, and several remarkable changes in form were observed while it 

 traversed half the disk, till its contraction to a black speck 1000 miles in 

 diameter, after which it was obliterated. The spot B had advanced some 

 distance on the disk, and was followed till the 21st of February, when it ap- 

 proached the edge, with indications of being a shallow concavity. It was 

 not observed to reappear. The spots A and C require longer notice, both 

 on account of their persistence through more than a rotation-period, and 

 because of the remarkable changes which they have undergone. 

 The spot D is now under observation. 



The spot A, visible from the 4th to the 16th of February, and again 

 reappearing early in March, was solitary, and approximately round, mea- 

 suring, on February 10, about 23,000 miles across the penumbra, and 

 about 8000 across the umbra. 



It had a clear brown tint over the whole penumbra, the body of the sun 

 appearing fairly white, and a deeper brown tint over part of the umbra, 

 the remaining and larger space of the umbra being black. The penunibral 

 space was marked with the broken structure represented in a former com- 



