6 'OUTLINES OF NATURAL PHILOSOPHY. 



pear single, are found, with higher magnifiers, 

 to consist of two, sometimes three or more 

 stars, extremely near to one another. 



a. Dr HERSCHEL has observed no less than 700 of 

 these multiple stars, of which only 42 were known 

 before. In some of them the small stars are dif- 

 ferent in brightness, and in the colour of their 

 light. Thus y Andromedae is double ; the stars 

 very unequal, the largest a reddish-white, the 

 smallest a sky-blue, inclining to green. See VINCE, 

 669. 



35. The fixed stars are not entirely exempt 

 from change ; several stars which are mention- 

 ed by the ancient astronomers having now ceas- 

 ed to be visible, and some being now visible to 

 the naked eye, which are not in the ancient ca- 

 talogues. 



a. It was the appearance of a new star that induced 

 HIPPARCHUS to begin his catalogue. A new star 

 which appeared in Cassiopeia's Chair, in 1572, 

 exceeded Sirius in brightness, and was seen at 

 noon-day. It did not change its place, but gradu- 

 ally decayed, and in about sixteen months disap- 

 peared entirely. It is supposed to have appeared 

 before in 945, and 1264. \ 7 iNCE, 704. 



b. A star of the same kind was seem by KEPLER in 

 1 604 ; and several similar facts are recorded. 



c t Algol, 



