The Systematic Motions of Sun-spots. 



13 



X and Table XI. These velocities are plotted gra2)liically in Fig. 

 4. Thé dotted curve in the same figure represents the mean 

 angular velocity, as computed from Maunder' s, SjoOrer's, and Car- 

 rington' s formula}. Its numerical values are given in the last 

 column of Table X. For the sake of convenience, the two drifts 

 corresponding to Maximum I and Maximum II will in the 

 remainder of this article be called. Drift I and Drift II respectively. 



Angular Velocities of Drift I and Drift II. 



Fig. 4. 



10 ^ 



14°H 14° 



14° 



14°4 



\Td 



i3°a 'i'^'i ^X(^ 



w?. 14°?. ]4°i wo 

 Angular Vtlocity 



6. On the whole, the angular velocities of Drift I, as 

 represented in Table X, accord very Avell with the mean values as 

 computed from the formuhie of the three investigators, though 

 there is a small systematic différence of about 0°.04 on the average. 

 In fact, the values obtained by these authors do not exactly rep- 

 resent the angular velocities of spot-groups of maximum occur- 

 rence. 



7. As to Drift II, it will be noticed from Table XI that there 

 is a rather considerable discrepancy in the values derived from the 

 Greenwich observations and from the other two, although there is 

 no great difference between the results deduced from Spörer's and 

 Carrington's observations. It is evident that the values at 

 latitudes 2°.5 and 27°.5 are of low vreights, the first being based 



