CHAPTER X. 



OBSERVATIONAL ASTRONOMY IN THE l8TH CENTURY. 



"Through Newton theory had made a great advance and was 

 ahead of observation ; the latter now made efforts to come once 

 more level with theory." BESSEL. 



196. NEWTON virtually created a new department of 

 astronomy, gravitational astronomy, as it is often called, 

 and bequeathed to his successors the problem of deducing 

 more fully than he had succeeded in doing the motions of 

 the celestial bodies from their mutual gravitation. 



To the solution of this problem Newton's own country- 

 men contributed next to nothing throughout the i8th 

 century, and his true successors were a group of Continental 

 mathematicians whose work began soon after his death, 

 though not till nearly half a century after the publication 

 of the Prindpia. 



This failure of the British mathematicians to develop 

 Newton's discoveries may be explained as due in part to 

 the absence or scarcity of men of real ability, but in part 

 also to the peculiarity of the mathematical form in which 

 Newton presented his discoveries. The Prindpia is written 

 almost entirely in the language of geometry, modified in 

 a special way to meet the requirements of the case ; nearly 

 all subsequent progress in gravitational astronomy has 

 been made by mathematical methods known as analysis. 

 Although the distinction between the two methods cannot 

 be fully appreciated except by those who have used them 

 both, it may perhaps convey some impression of the differ- 

 ences between them to say that in the geometrical treatment 

 of an astronomical problem each step of the reasoning is 



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