THE STARS. 155 



the Cape of Good Hope. But the climate of 

 South Africa did not suit his health, and after 

 a year he returned to Scotland. In 1834 he 

 became Professor of Astronomy in the Uni- 

 versity of Edinburgh, and Astronomer-Royal of 

 Scotland, which position he held till his death 

 on November 23, 1844, at the early age of 

 forty-six. 



During a year's work at the Cape, Hender- 

 son undertook a series of observations on the 

 bright southern star, a Centauri, with a view 

 to determining its parallax. These observations 

 were made in 1832 and 1833, but were not 

 reduced until Henderson's return to Scotland. 

 At length, on January 3, 1839, he announced 

 to the Royal Astronomical Society that he 

 had succeeded in measuring the parallax of 

 a Centauri, which he determined as about one 

 second of arc, corresponding to a distance of 

 about twenty billions of miles. This result 

 was confirmed by the observations of Thomas 

 Maclear (1794-1879), his successor at the Cape, 

 and by those of later observers, notably Sir 

 David Gill, who has reduced the parallax to 

 075". 



Other determinations of stellar parallax, some 

 genuine and others illusory, were made soon after 

 these successful observations. C. A. F. Peters 



