214 HISTORY OF PHYSICAL ASTRONOMY. 



For the same reason we pass over many events 

 of this period which are highly important in the 

 history of astronomy. They have lost much of 

 their interest for us, and even for common read- 

 ers, because they are of a class with which we are 

 already familiar, truths included in more general 

 truths to which our eyes now most readily turn. 

 Thus, the discovery of new satellites and planets 

 is but a repetition of what was done by Galileo : 

 the determination of their nodes and apses, the 

 reduction of their motions to the law of the ellipse, 

 is but a fresh exemplification of the discoveries 

 of Kepler. Otherwise, the formation of Tables of 

 the satellites of Jupiter and Saturn, the discovery 

 of the eccentricities of the orbits, and of the mo- 

 tions of the nodes and apses, by Cassini, Halley, and 

 others, would rank with the great achievements 

 in astronomy. Newton's peculiar advance in the 

 Tables of the celestial motions is the introduction 

 of perturbations. To these motions, so affected, 

 we now proceed. 





Sect. 2. Application of the Newtonian Theory to 

 the Moon. 



THE Motions of the Moon may be first spoken of, 

 as the most obvious and the most important of the 

 applications of the Newtonian Theory. The veri- 

 fication of such a theory consists, as we have seen 

 in previous cases, in the construction of Tables 



