150 



Dr. W. J. S. Lockyer. 



[Jan. 16, 



to continually approach the equator, but superposed upon the line of 

 uniform descent was a series of minor oscillations. In this connection 

 he wrote :* " Die Sporer'sche Entdeckung der in jeder Periode 

 auftretenden Annaherung der Flecken-Zone gegen den Aequator findet 

 somit in unsern Beobachtungen eine unmisskennbare Bestatigung. 

 Allerdings sine! die Zeichnungen nicht clurchaus von demselben Gehilfen 

 ausgefiihrt worden, und dieser Umstand mag einigen Einfluss in Bezug 

 auf diese Wahrnehmung haben . . . Sehr aufFallend erscheint 

 eine gewisse secundare periodische Schwankung der mittleren Breite 

 mit einer Periode von etwa 1 Jahr und einer Amplitude von reichlich 

 2 Graden . . . Diese mag wohl einem Zufall zuzuschrieben sein, 

 welche nur wahrend dieser vier Jahre obwaltete, vielleicht auch mit 

 clem Wechsel der Zeichner in Zusammenhang steht. Doch ware es 

 immerhin von Interesse, dass diese Wahrnehmung durch die Discussion 

 anderweitiger Beobachtungen gepriift und eventuell naher untersucht 

 wiirde." 



The present investigation seems to throw light on these peculiar 

 changes of curvature shown by the mean heliographic latitude curves. 

 These latter (Plates 4 and 5, Curves B) are individually really nothing 

 more than the integration of the corresponding Curves A. Every 

 change of curvature in Curves B is due to either the outburst of spots 

 in another "spot-activity track" or by one "spot-activity track" 

 becoming more intensified in relation to another, or lastly by the 

 extinction of a " spot-activity track " as the equator has been reached 

 as shown in the Curves A. 



To illustrate this, let the curve for the mean heliographic spot 

 latitude in the southern hemisphere (Plate 5, Curves B) beginning in 

 the year 1879 be considered. This is practically the period referred to 

 above by Dr. Braun. 



At this time there is only one " spot-activity track " (latitude 22°) 

 in existence, as shown in Plate 5, Curve A ; so Curve B consequently 

 commences in the same latitude. By the next year the " spot-activity 

 track " (Curves A) has reached latitude 17°, and a new one has made its 

 appearance in latitude 25°. Curve B, therefore, takes the mean position 

 of about 20°, when allowance has been made for the difference of 

 intensity of these two tracks. 



In the following year 1881 both these "spot-activity tracks "have 

 approached nearer the equator, but another has appeared in latitude 25°, 

 so that the mean latitude for the whole hemisphere has only slightly 

 changed. 



By the year 1882 still another "spot-activity track" has come into 

 existence in latitude 28°, while the first " spot-activity track " mentioned 



* Ibid., p. 83. 



