Eight-Year Cycle in Relation to Physical Cause 105 



by his English contemporary, Mr. Manuel Johnson, 

 President of the Royal Astronomical Society: 



"His plan is to note by a number each spot in 

 the order of its appearance, carrying on his nota- 

 tion from the first to the last spot in each year. He 

 reckons an isolated spot or a cluster of spots where 

 there is no visible separation between their penum- 

 brae, as one group. 'Hence,' he observes, 'the num- 

 ber of spots will depend in a great measure on the 

 excellence of the telescope; and it often happens 

 that the clusters of many hundred, nay, of many 

 thousand spots, will be designated by one number 

 only, just as a single isolated spot will be. So great, 

 however, is the Sun's tendency to present his spots 

 in the form of clusters, that observers will in the 

 course of a year, assuredly not find any great dif- 

 ference between their numbers and mine.' But he 

 particularly impresses his reader that he attaches 

 importance not so much on the absolute number of 

 groups, as on the ratio which obtains between them 

 in different years." 



For ten years Schwabe's daily countings of the sun- 

 spots were published annually in the Astronomische 

 Nachrichten apparently without attracting any atten- 

 tion. In 1838 he grouped his annual observations 

 for the period 1826-1837 but forebore to indicate a 

 periodicity, and his researches were still ignored by 

 his fellow astronomers. For five more years he con- 

 tinued to publish his records annually when in 1843 

 he made the announcement of periodicity in his data. 



