452 



Solar Prominence and, Spot Circulation. 



[Mar. 17, 



this curve with that representing the changes of latitude of the 

 zones of prominences. In every case, arid for each hemisphere, the 

 subsidiary maxima are coincident in time with the presence of two 

 zones of prominences, each well-developed, while at the principal 

 minima only one zone is in evidence. 



We have already explained the fact that spots are restricted to a 

 zone having its limits at latitudes ± 5° and ± 35°, while prominences 

 occur all over the sun's disc, even up to the poles, and also that spots 

 always commence their cycle in high latitudes (about ± 35°) and 

 gradually approach the equator until within 5°, when a new cycle is 

 commenced in high latitudes. Prominences on the other hand begin in 

 comparatively low latitudes (about ± 24°), and finish their cycle near 

 the poles. 



A glance at the Plates 6 and 7 brings out the interesting fact that 

 at sunspot minima, when two zones of spots are in evidence, there is 

 only one zone of prominences, while when only one zone of spots 

 exists the prominences are for the most part confined to two zones. 



The conclusions arrived at in the present communication may be 

 summarised as follows : — 



1. The centres of action of prominence activity undergo an appa- 

 rently regular variation. 



2. The direction of motion of these centres is from low to high 

 latitudes, the reverse of that of spots, which travel from high to low 

 latitudes. 



3. At epochs of prominence minima (which are concurrent with 

 sunspot minima) these centres of action are restricted to one zone 

 (about latitude ± 44°) in each hemisphere, while those of the spots 

 occupy two zones in each hemisphere. 



4. At nearly all other times these centres are apparent in two 

 zones, while those of the spots occupy only one in each hemisphere. 



5. The subsidiary maxima exhibited by the curves representing the 

 percentage frequency of prominence activity for each entire hemi- 

 sphere, are due to the presence of two well-developed centres t)f pro- 

 minence activity in each hemisphere. 



