Masterpieces of Science 



In these pages any account of his work would 

 be out of place. We need only dwell upon the 

 result, and upon other discoveries which have 

 been made by observers who have taken up the 

 same work. 



Schwabe found that in the course of about 

 eleven years the solar spots pass through a com- 

 plete cycle of changes. They become gradually 

 more and more numerous up to a certain max- 

 imum, and then as gradually diminish. At 

 length the sun's face becomes not only clear of 

 spots, but a certain well-marked darkening 

 around the border of his disk disappears alto- 

 gether for a brief season. At this time the sun 

 presents a perfectly uniform disk. Then grad- 

 ually the spots return, become more and more 

 numerous, and so the cycle of changes is run 

 through again. 



The astronomers who have watched the sun 

 from the Kew Observatory have found that the 

 process of change by which the spots sweep in a 

 sort of "wave of increase" over the solar disk 

 is marked by several minor variations. As the 

 surface of a great sea-wave will be traversed by 

 small ripples, so the gradual increase and diminu- 

 tion in the number of the solar spots is charac- 

 terized by minor gradations of change, which 

 are sufficiently well marked to be distinctly 

 cognizable. 



There seems every reason for believing that 

 the periodic changes thus noticed are due to the 

 influence of the planets upon the solar photo- 

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