164 HISTORY OF ASTRONOMY. 



Mr. Maclear, at the Cape of Good Hope, for the purpose 

 of ascertaining the parallax of this star. The observations 

 consisted of double altitudes measured with the mural 

 circles, and they gave a parallax of 0".91 ; and from sub- 

 sequent observations extending down to 1848, he found 

 it to be 0".98. 



Mr. Maclear also made a series of observations of ft 

 Centauri, in the years 1842-44, from which he has de- 

 duced a parallax for this star amounting to 0".47, with a 

 probable error of 0".04. 



In the year 1835, M. Struve commenced a series of ob- 

 servations, with a view of detecting the parallax of the 

 bright star a Lyrse. His method of observation consisted 

 in measuring with a micrometer the distance between this 

 star and another very small star situated about 43" from 

 it, repeating the operation at different seasons throughout 

 the year. The result of this inquiry assigned a parallax 

 of 0".26 toaLyrae. 



The more recent researches of M. Peters at the Pul- 

 kova observatory tend to prove that this star has a visible 

 parallax, although the result is less than that assigned 

 by M. Struve. These observations were made with the 

 great vertical circle of Ertel, and his result was a 

 parallax of 0".10, with a probable error of 0".05. 



M. Otto Struve has recently given the result of fifteen 

 months' observations on this star, and finds a parallax 

 of // .14. Combining this result with the former values 

 of M. Struve and Peters, he obtains a mean value of 

 0".15, with a probable error of 0".01. 



