Summary. 



The present investigation of the motions of tlie sun-spots is based on measure- 

 ments of the co ordinates of the spots during the period 1886 — 1909 published in the 

 Greenwich Observations. From these measurements the motions of the spots 

 have been computed in minutes of arc per hour. All such spots are included in 

 the investigation as have been observed within 60° from the central meridian for at 

 least two consecutive days, and the motion of which in longitude and latitude is 

 smaller than 10' and 5' respectively, corresponding to a linear velocit}^ of 82 and 41 

 km. per hour. 



I shall here give a summary of the results obtained, based, for the most part, 

 on no less than 16742 observations of loiigitude and latitude motions. 



1. The daily mean area of the sun-spots A expressed in millionths of the sun's 

 visible disk may be computed with considerable accuracy from the relative 

 numbers r of Wolf by means of the formula 



A = 7.466 ■ r '-'"^ (Page 5). 



2. The »latv of Sporer» is positively confirmed from the table on page 14. 



3. The distribution of the motions in longitude as well as in latitude is attended 

 by a considerable positive excess, which still remains unexplained. The 

 skewness, on the contrary, is, upon an average, equal to zero. There exists 

 possibly an inconsiderable decrease of the skewness of the motions in longitude 

 with increasing distance from the equator (Table XII). The dispersion of the 

 longitude motions is double the size of the dispersion of the motions in latitude. 

 (Page 28, 33, 59). 



4. On account of the considerable dispersion, the angular velocity cannot be 

 determined with great accuracy. The daily rate of the sun's rotation is 

 obtained from the following formulée: 



First Period (1886—1900) : F= 14».577 + 0°.096 sin ß — 2°. 322 sin ; 

 Second Period (1898—1909) : V = 140.489 — 0«.076 sin ß — 2«.i66 sin ^ß. 



By way of comparison the following formulas may be mentioned here. 



Carrington (1853—1861): F= 14''.417 — 2<'.750 sin '/'ß ; 



Sporer (1861—1871): F= 80.532 -f 50.798 cos ß ; 



Maunder (1879- 1901): F = 14^.443 — 2°.l33 sin =ß. 



