Mr Herschel and Mr South's Observations on Stars. 281 



equilibrium. I have the honour to be, your humble and 

 obedient servant, 



Seguin ain£. 

 Annonay, Dep. de VArdeche, 

 March 28, 1825. 



Art. XIV. — Observations on the apparent Distances and 

 Positions of 389 Double and Triple Stars. By J. F. W. 

 Herschel, Esq. Sec. R.S. Lond. and F.R. S. Edin., and 

 James Sooth, Esq. F. R.S. Lond. and Edin. 



More than forty years ago, the late celebrated Sir W. 

 Herschel directed the attention of astronomers to the im- 

 portance of determining the distances and positions of double 

 stars ; and during the years 1779 and 1784, he published in 

 the Philosophical Transactions, descriptions and names of 

 702 double and triple stars. The result which he obtained 

 in this inquiry, may be considered as forming an entirely new 

 department of physical astronomy, in wiiich the agency of 

 attractive forces has been found to exist in the remotest 

 regions of the sidereal universe. 



It was fortunate for astronomy, that a subject of such in- 

 terest was taken up by his son, whose mathematical acquire- 

 ments, and habits of nice observation, fitted him in a peculiar 

 manner for the task, and that he was aided by such an excellent 

 observer as Mr South. The object with which these gentlemen 

 commenced this inquiry, was to determine the existence and 

 amount of annual parallax, but this was soon lost sight of 

 amid the more extensive views of the construction of the uni- 

 verse, which gradually unfolded themselves. They have 

 clearly established the existence of binary systems, in which two 

 stars perform to each other the offices of sun and planet. 

 They have ascertained with considerable exactness the periods 

 of rotation of more than one such pair. They have observed 

 the immersions and emersions of stars behind each other ; and 

 they have detected among them real motions sufficiently rapid 

 to become measurable quantities in very short intervals of 

 time. 



