286 A Short History of Astrcnomy [Cn. x., $ 2 7 



a number which long remained classical. The uncertainty 

 of the data is, however, shewn by the fact that other equally 

 competent astronomers have deduced from the observations 

 of 1769 parallaxes of 8"'8 and 8"'9. 



No account has yet been given of William Herschel, 

 perhaps the most famous of all observers, whose career 

 falls mainly into the last quarter of the i8th century and 

 the earlier part of the iQth century. As, however, his 

 work was essentially different from that of almost all the 

 astronomers of the i8th century, and gave a powerful 

 impulse to a department of astronomy hitherto almost 

 ignored, it is convenient to postpone to a later chapter (xn.) 

 the discussion of his work 



