186 MR. JOSEPH BAXENDELL ON THE 



XI. — On the Phenomena of Groups of Solar Spots, 

 By Joseph Baxendell, F.R.A.S, 



Eead before the Physical and Mathematical Section, 

 October 13th, 1859. 



It is well known that the spots on the sun generally occur 

 in groups, which differ considerably in size and form, and 

 in the duration of their appearance ; and which frequently 

 undergo great changes in short intervals of time. Although 

 they have long engaged the attention of astronomers, little 

 progress has yet been made in the investigation of the 

 laws which regulate their formation and their diversified 

 appearances and changes. It has long been known that 

 they occur principally in two bands or zones parallel to the 

 solar equator, and that they are rarely seen beyond the 

 limits of 35° north and south latitude ; and Mr. Carrington 

 has shown that the position in latitude of these zones is 

 subject to considerable and rather sudden changes. M. 

 Schwabe^s long series of observations has proved that there 

 is a pretty regular period of increase and decrease in the 

 number of the solar spots. Mr. Dawes and Professor 

 Secchi have observed that large spots have sometimes a 

 movement of rotation; and Dr. C. H. F. Peters and Mr. 

 Carrington have pointed out that the individual spots of 

 small groups have a tendency to diverge or recede from 

 each other. There are^ however, certain phenomena of 

 groiips of spots which, so far as I am aware, have not 



