PORTION OF THE COSMOS. MULTIPLE STARS. 201 



double stars, exclusive of such as are more than 32 /x apart ; 

 now, a hundred years later (thanks principally to the great 

 labours of the two Herschels and Struve), there have been 

 discovered in both hemispheres about 6000. Among the 

 earliest described double stars, ( 332 ) are Ursse maj. (7th 

 Sept. 1700, by Gottfried Kirch), a Centauri (1709, by 

 Eeuillee), y Virginia (1718), a Geminorum (1719), 61 

 Cygni (1753, the distances and angles of direction were 

 observed in this and the two preceding cases by Bradley), 

 p Ophiuchi, and % Cancri. The number of double stars 

 enumerated gradually augmented, from Plamsteed who 

 employed a micrometer, to the Star Catalogue of Tobias 

 Mayer, which appeared in 1756. Two men, sagacious in 

 conjecture and apt in combination of thought, Lambert 

 (" Photometria," 1760 ; and " Cosmological Letters on the 

 Arrangement of the Structure of the Universe/' 1761), and 

 John Michell (1767), although they did not themselves 

 observe double stars, were the first who promulgated just 

 views respecting the relations of attraction of stars in partial 

 binary systems. Lambert, like Kepler, ventured to suppose 

 the distant suns (fixed stars), to be, like our own sun, sur- 

 rounded by dark bodies, as planets and comets, but respect- 

 ing fixed stars in near proximity to each other, (although he 

 otherwise seems inclined to entertain the supposition also of 

 dark central bodies), his belief was, ( 333 ) that they performed 

 within a moderate time a revolution around their common 

 centre of gravity. Michell, ( 334 ) who had no knowledge of 

 Kant's and Lambert's ideas, was the first who, with much 

 sagacity, applied the calculus of probabilities to close groups 

 of stars, especially to multiple stars, binary and quaternary. 

 He showed the probabilities to be 500,000 to 1 against the 



