448 Sir Norman Lockyer and Dr. W. J. S. Lockyer. [Mar. 17, 



zones of spots existing at one time, so there might be one, two, or 

 occasionally three zones of prominences in existence in each hemisphere 

 simultaneously. 



Further, a close examination 

 of the whole set of curves with 

 reference to these points of 

 maxima made it possible not 

 only to study the changes of 

 latitude of these points from 

 year to year and their positions 

 when commencing to develop or 

 about to disappear, but the in- 

 tensity of these centres in rela- 

 tion to each other. 



The accompanying illustration 

 (fig. 1) shows the curves drawn 

 for the years 1879, 1880, and 

 1881, from the observations of 

 Tacchini, and serves as an ex- 

 ample of the curves that have 

 been discussed ; they exhibit the 

 change from a single to a double 

 centre of activity in each hemi- 

 sphere. 



Thus in 1879, there was a 

 prominence maximum in each 

 hemisphere at latitudes ± 50°. 

 In the next year (1880), both the 

 maxima had retreated further 

 away from the equator, namely 

 to latitudes ± 60°, while another 

 centre of disturbance began to 

 make itself apparent at latitudes 

 ± 30°. In the year 1881, both 

 centres in each hemisphere were 

 strongly marked and became of 

 about the same intensity, their 

 mean latitudes in each hemi- 

 sphere being about ± 30° and 

 ± 60°. These curves thus indi- 

 cate that during these three 

 years, the direction of motion of these centres of activity tends pole- 

 wards or away from the equator. 



By examining both series of observations made by Tacchini and 

 Kicco and Mascari, and analysing the positions of the principal and 



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