1904.] Sunspot Variation in Latitude, 1861 — 1902. 



151 



above has vanished. The mean latitude for the whole hemisphere, as 

 is indicated in Curve B for this epoch, is increased to latitude 20 3 . 

 After this all three " spot-activity tracks " approach the equator and 

 Curve B does the same, but owing to the relative changes in the 

 amount of the spotted area in each of these " spot-activity tracks " as 

 indicated by their thickness, the mean heliographic latitude curve 

 suffers another change of curvature in 1885. In a similar way the 

 various changes of curvature in all the other curves (Curve B) can be 

 accounted for. 



Particular attention has been drawn to the fact that about the times 

 of sunspot maxima there is considerable spot activity in the highest 

 spot latitudes, which according to Sporer's law would not be expected. 



The following extract expressing the impressions of Messrs. De La 

 Bue, Stewart and Loewy on this point is therefore of interest, since 

 it shows that such activity at the maximum of 1871 was even remarked 

 as long ago as 1872.* " A striking feature of last year's observations 

 seems to have been the occurrence of groups in comparatively high 

 latitudes, especially in the southern solar hemisphere ; a group 

 observed between March 21 and 23 had the almost unprecedented 

 high latitude of 43°, while latterly, towards the end of the year, 

 several groups in almost as high a latitude have repeatedly made 

 their appearance.' 5 



The Wilna observers also drew attention to the high latitudes of 

 some spots about this maximum period, 1869 — 1871, as can be 

 gathered from the following extract.! 



" Generally speaking, during the last three years, about the last 

 maximum, the spots were most distant from the equator ; five spots 

 were observed near latitude 38° ; three about latitude 40 — 43° ; one 

 at 51J° latitude, . . ." 



A word may finally be said as to the relationship between the curves 

 representing the " spot-activity tracks " (Curves A), and those 

 indicating the "prominence-activity tracks" (Curves C). As was 

 pointed out in a previous communication £ the general drift of the 

 prominence activity is from low to high latitudes. 



It is of interest here to note that from the time of a sunspot 

 minimum when the " prominence-activity tracks " are approaching more 

 rapidly high latitudes, up to about a sunspot maximum when they 

 reach their highest positions, nearly all the " spot-activity tracks " come 

 into existence. Further, the nearer the "prominence-activity tracks" 

 approach the poles the higher in latitude do these " spot-activity 

 tracks " also occur, and this is the case for each hemisphere of the 

 sun separately. 



* ' Monthly Notices K. A. S.,' 1872, vol. 32, p. 225. 

 t ' Report of the Committee on Sola** Physics,' 1882, p. 155. 

 | ' Roy Soc. Proc.,' vol. 71, p. 452. 

 VOL. LXXIII. M 



