DOUBLE STARS 219 



them are not merely double in appearance, but must be 

 allowed to be real binary combinations of two stars, inti- 

 mately held together by the bond of mutual attraction." 



Herschel's first catalogue of double stars was pre- 

 sented to the Royal Society in a memoir of fifty pages 

 on January 10, 1782. It was a work of enormous 

 labour to be undertaken and carried out by a hard- 

 working musician during the nights, that followed 

 days of absorbing business. Of the number 269, con- 

 tained in this catalogue, 227 had not been noted by any 

 astronomer before him. It was not only a new field 

 of research he may be considered to have opened up. 

 He had also two distinct ends in view, which may be 

 said to have been equally novel. One of them was, 

 by means of these double or triple systems, to discover 

 the distances of the stars from our sun, and the other 

 to ascertain whether " small stars revolved round large 

 ones." He failed in the former, he was successful in 

 the latter. The arithmetic of the one was too hard for 

 him ; the poetry of the other was reduced to the 

 commonplace of fact, after a waiting period of twenty- 

 five years. 



Everyone knows that if a tree and a house be 

 in the same line of sight from a distant spectator, 

 the eye of the spectator may imagine the tree to 

 be at the same distance as the house, but cannot 

 measure the space between them. We cannot see 

 distance; it is an acquirement gained by experience 

 from the sense of touch, and gained so insensibly that 

 we think we see distance in front of us, height or 

 depth, it may be, while, in fact, we only see length and 

 breadth. An observer, seeing two stars so close that, 

 to the naked eye, they seem only one, may consider 



