252 



CAUSE OF THE CHANGES OF RELATIVE 



IV. 



Account of the Changes that have happened, during the laji Twenty" 

 five Years, in the relative Situation of Double Stars ; xvith aii 

 Invefiigation of the Caufe to which they are owing. By Wil- 

 liam Her scHEL, LL. D. F, R. S, From the Philofophical 

 Jranfaaiom for 1 803 . * 



(Concluded from Page 221.) 



I 



Obfervationsand J[ SHALL now enter into a more detailed examination of the 

 ipefting the feveral angles of pofition I have taken at different times, and 

 changes of rela- fhow that they agree perfeflly well with the appearances which 



tlve fituatlon in 



rauft ari(e from the revolution of a fmall ftar round Caftor. A 



ftars extremely 



near each other, calculation of thefe angles may be had, by finding the annual 



motion of the fmall ftar, from the change of 21® 54'', which has 

 been fliown to have taken place in 23 years and 142 days. 

 Accordingly, I have given^ in the firft column of the following 

 table, the lime when the angles were taken. In the fecond, 

 are, the angles as they were found by meafure ; they are all in 

 the norJ,}»-pi"eceding quadrant. The third column contains a 

 calculation from the annual motion of 56^,18, obtained as before 

 mentioned: it (hows what thefe angles fliould have been, ac- 

 cording to our prefent fuppofition of a revolving ftar. And 

 the laft column gives the difference between the obferved and 

 calculated angles. 



On 



