CHAPTER IL 



The Longitude Motions of the Sun-spots. 

 A. The Classification of the Observations. 



In order to be able to examine the motions in longitude as well as in latitude 

 the whole material must first be divided into classes according to AX cos ß and Aß. 

 (For the meaning of this notation see page 20). 



This classification was done in the following manner. The whole material of 

 observation was first classified according to years. In each year the cards were 

 afterwards distributed according to the latitudes of the spots, so that all the spots 

 the latitudes of which satisfied the relation 



0".c < ß < + 2".4 

 were taken together, and in the same way all those where 



4- 2^5 < ß < -f 4".o etc. 

 For the southern hemisphere the limits of the classes were determined from 



— 0°.] >ß> — 20.5 etc. 

 The number of cards in each such class will be seen in table IV. 



To begin with I was uncertain whether it would be necessary to divide the 

 material into latitude-zones as narrow as 2". 5. I fixed, however, on this class-interval. 

 Should it prove during the progress of the work that a class-interval of 5°.o was 

 sufficient it would then be an easy matter to conjoin the classes. 



When this classification into latitude-zones of all the years comprised in the 

 investigation had been performed we could proceed to arrange the material in each 

 such zone according to the motions in longitude and latitude, i. e. according to 

 AX cos ß and Aß. In the classifying of the material according to the size of AX cos ß 

 I fixed on a class-interval of I'.o. As it proved that the motions in latitude amounted 

 to about half this value, I chose the class-interval for this classification at 0'.5. 

 The class where 



— I'.o < AX cos ß < — O'.i 



was indicated by 0. 



