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2. A great number ot groups may be regarded as consist- 
ing of two sub-groups, each containing one or two spots 
decidedly larger than the rest. These sub-groups may in 
their early stages have no apparent connexion, but sooner or 
later small spots generally break out in the interval between 
them and complete the group. 'The preceding sub-groups of 
binary groups are generally the first to appear and the last 
to disappear. Amidst all the changes to which groups of 
spots are liable, there seems to be a general tendency to 
assume the binary arrangement; and it often happens that 
groups which have apparently quite lost their original binary 
character, again resume it before their final decay and extinc- 
tion. Mr. Williamson’s diagrams contain many groups 
which exhibit the binary character; and from the descrip- 
tions of the solar spots given by former observers, there 
can be little doubt that groups of this class have at all times 
been of common occurrence. An observation of Sir William 
Herschell, in January, 1801, is quoted as an illustration. 
The two centres of force or activity in binary groups are 
sometimes very widely separated, instances not uncommonly 
occurring in which the distance between them exceeds 90,000 
miles. 
3. Groups which exhibit anomalous appearances, and 
undergo complicated changes, sometimes consist of two 
binary groups which have originally broken out near each 
other and have extended themselves until they form one 
compound group. 
4. Spots which exhibit indications of rotation are generally 
the principal members of preceding sub-groups ; but the 
Author considers that his observations are far from being 
conclusive as to whether this rotation is real or only apparent. 
It is difficult to conceive the mode of operation by which 
the forces that produce the spots in a binary group should 
first devclopc themselves — sometimes almost simultaneously — 
at fivo points so widely distant from each other; and the 
