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XXXII. On the Calculation of the Orbits of Double Stars. 



By Professor ENCKE*. 



TT was the immortal Herschel who, among his many grand 

 - views, first directed the attention of astronomers to the 

 highly remarkable phenomenon that so many stars are placed 

 closely together, and to the conclusion which he drew from 

 this circumstance, that there is great probability that two such 

 stars, separable only by highly magnifying telescopes, are not 

 only apparently near each other, owing to the place whence 

 they are viewed, but that they really form in space a coordinate 

 system ; that they act upon one another, and in consequence 

 undergo changes in their relative positions, which, after longer 

 or shorter intervals, may be capable of observation, and whose 

 laws may be developed in the course of time ; and from that 

 moment a new field has been opened for practical astronomy, 

 the extent of which it is not yet possible to determine. Herschel 

 was not satisfied with merely advancing this hypothesis, but 

 he, in the beginning of his career, thoroughly examined the 

 heavens, and recorded a number of observations on the rela- 

 tive positions of stars thus placed closely together, in order to 

 transmit to future times safe points of comparison; and he en- 

 joyed the satisfaction of learning, that on a new examination, 

 after a lapse of more than twenty years, such sensible changes 

 were observed, in several double stars, as left no doubt re- 

 garding the truth of his hypothesis. After him, Struve ofDorpat 

 first resumed these investigations, confirmed the observations 

 of Herschel, and after a due appreciation of his wonderful 

 zeal, and the eminent skill evinced by him in the management 

 of inferior means, he obtained, in the great refractor of 

 Frauenhofer, one of the most powerful instruments for accu- 

 rately investigating this subject. Herschel (the son), and South, 

 had in the mean time likewise devoted their eminent talents 

 to the observation of double stars; and since the new cata- 

 logue of Struve has proved the vast number of such systems ; 

 since the comparison of the observations made with different 

 instruments, and after different methods, promises a by far 

 greater degree of accuracy than was formerly expected ; since, 

 lastly, practical optics, in England, France, and Germany 

 have, with regard to the size of instruments and the distinct- 

 ness of images, reached a perfection hitherto deemed unattain- 

 able, the observations of double stars have obtained much 

 additional interest. 



Our experience is, indeed, as yet too short to derive from 

 it any thing permanently correct; the whole space of time to 



* From Encke's Ephemeris, for 1832. 



which 



