PHENOMENA OF GROUPS OF SOLAR SPOTS. 187 



been alluded to in any astronomical work or memoir, but 

 which seem to me to merit attention, as indicating the 

 direction in which future inquiries ought to be made ; and 

 I have therefore thought that a brief notice of them might 

 not be unacceptable to the members of this section. 



The first point to which I would draw attention is the 

 fact that in those groups, which consist of spots differing 

 considerably in size, the largest spot is generally in the 

 preceding part of the group. An examination of such 

 published drawings and descriptions of the solar spots by 

 other observers as have fallen under my notice has con- 

 firmed the conclusion drawn from my own observations ; 

 and in a series- of unpublished diagrams of the solar spots 

 made by my friend Mr. Williamson of Cheetham Hill, in 

 the years 1849, 1851, and during the present year, and 

 which he has kindly allowed me to inspect, I find that out 

 of thirty- one difierent groups only four had the largest 

 spot in the following part of the group, the ratio of excep- 

 tions to the rule being therefore about one to seven. My 

 own observations indicate a much smaller ratio, and I 

 must remark that as Mr. Williamson's principal object 

 was to show the positions of the groups on the solar disc 

 and not to delineate very exactly their details, many of 

 the groups laid down in his diagrams do not exhibit any 

 very decided difference of size in their components, and 

 are therefore not available for the purposes of this branch 

 of the inquiry. 



The next feature in the constitution of groups of spots 

 to which I have to allude is, that a great number of these 

 groups may be regarded as consisting of two sub-groups^ 

 each of which generally contains one or two spots deci- 

 dedly larger than the rest. In their early stages these 

 sub-groups have often no apparent connexion, but after a 

 certain time small spots break out in the interval between 

 them, and form an irregular line or band which completes 



