224 HISTORY OF PHYSICAL ASTRONOMY. 



wards. In 1720, when Louville refused to allow in 

 his solar tables the motion of the aphelion of the 

 earth, Fontenelle observed that this was a misplaced 

 scrupulousness, since the aphelion of Mercury cer- 

 tainly advances. Yet this reluctance to admit 

 change and irregularity was not yet overcome. 

 When astronomers had found an approximate and 

 apparent constancy and regularity, they were will- 

 ing to believe it absolute and exact. In the satel- 

 lites of Jupiter, for instance, they were unwilling to 

 admit even the eccentricity of the orbits ; and still 

 more, the variation of the nodes, inclinations, and 

 apsides. But all the fixedness of these was succes- 

 sively disproved. Fontenelle in 1732, on the occa- 

 sion of Maraldi's discovery of the change of inclina- 

 tion of the fourth satellite, expresses a suspicion 

 that all the elements might prove liable to change. 

 " We see," says he, " the constancy of the inclination 

 already shaken in the three first satellites, and the 

 eccentricity in the fourth. The immobility of the 

 nodes holds out so far, but there are strong indica- 

 tions that it will share the same fate." 



The motions of the nodes and apsides of the 

 satellites are a necessary part of the Newtonian 

 theory; and even the Cartesian astronomers now 

 required only data, in order to introduce these 

 changes into their Tables. 



The complete reformation of the Tables of the 

 Sun, Planets, and Satellites, which followed as a 

 natural consequence from the revolution which 



