44 A CENTURY'S PROGRESS IN ASTRONOMY. 



years of observation was published in Hum- 

 boldt's ' Cosmos,' and Schwabe was able to show 

 that the spots increased and decreased in a period 

 of about ten years. Astronomers at once recog- 

 nised the importance of Schwabe's work, and 

 in 1857 he was rewarded by the Gold Medal 

 of the Royal Astronomical Society of London. 



Rudolf Wolf (1813-1892) of the Zurich Ob- 

 servatory now undertook to search through the 

 records of sun-spot observation, from the days 

 of Galileo and Scheiner, to find traces of the 

 solar cycle discovered by Schwabe. He was 

 successful, and was enabled to correct Schwabe's 

 estimate of the length of the period, fixing it as 

 on the average 11 '11 years. Additional interest, 

 however, was given to Schwabe's and Wolf's 

 investigations by the remarkable discoveries 

 which followed. In September 1851 John 

 Lamont (1805-1879), a Scottish astronomer, 

 born at Braemar in Aberdeenshire, but employed 

 as director of the Munich Observatory, after 

 searching through the magnetic records collected 

 at Gottingen and Munich, discovered that the 

 magnetic variations indicated a period of 10^- 

 years. Soon after this Sir Edward Sabine 

 (1788-1883), the English physicist, from a dis- 

 cussion of an entirely different set of obser- 

 vations, independently demonstrated the same 



