162 GALILEO AND HIS JUDGES. 



apparent force, which no one now would attribute 

 to it. Galileo himself had some hope of overcoming 

 the difficulty by discovering some annual displace- 

 ment in certain stars, but it is needless to add that 

 his instruments were unequal to such a task. Sub- 

 sequent observers tried various methods, but 

 without any real success until the present century, 

 when Bessel and other observers found that a star 

 called 61 Cygni had a certain annual parallax ; and 

 not long afterwards, Henderson, making his obser- 

 vations at the Cape of Good Hope on a conspicuous 

 star in the constellation of the Centaur, a constel- 

 lation belonging to the southern hemisphere, found 

 at length that this star, which in fact is a double 

 star, and known as a Centauri, had a parallax of 

 nearly 1" ; subsequent calculations show it to be 

 probably rather less, that is to say about O'"91. This 

 means that it is more than twenty billions of miles 

 distant, and that light takes more than three years to 

 travel from a Centauri to the earth. It is, however, 

 believed to be much the nearest of all the stars, no 

 other coming within double of the distance. 



Now it is difficult to evade the conclusion which 

 naturally follows from these results, that the Earth 

 really does move in an annual orbit round the Sun. 

 It is no part of my present task to give a list of the 

 stars of which the parallax has been found, but I 

 may say there are several others besides the two I 

 have named ; and I know of no method of accounting 



