PHYSICAL ASTRONOMY. 553 



tiou of the Xode of the Moon's orbit, coinciding exactly with one which 

 had been found to appear in the observations; 



Nothing can more strikingly exhibit the confirmation which in- 

 creased scrutiny brings to light between the Newtonian theory on the 

 one hand, and the celestial motions on the other. We have here a 

 very large mass of the best observations which have ever been made, 

 systematically examined, with immense labor, and with the set pur- 

 pose of correcting at once all the elements of the Lunar Tables. The 

 corrections of the elements thus deduced imply of course some error 

 in the theory as previously developed. But at the same time, and 

 with the like determination thoroughly to explore the subject, the the- 

 ory is again pressed to yield its most complete results, by the invention 

 of new and powerful mathematical methods; and the event is, that 

 residual errors of the old Tables, several in number, following the most 

 diverse laws, occurring in several detached parts, agree with the residual 

 results of the Theory thus newly extracted from it. And thus every 

 additional exactness of scrutiny into the celestial motions on the one 

 hand and the Newtonian theory on the other, has ended, sooner or 

 later, in showing the exactness of their coincidence. 



The comparison of the theory with observation in the case of the 

 motions of the Planets, the motion of each being disturbed by the 

 attraction of all the others, is a subject in some respects still more 

 complicated and laborious. This work also was undertaken by the 

 same indefatigable astronomer ; and here also his materials belonged 

 to the same period as before ; being the admirable observations made 

 at Greenwich from 1750 to 1830, during the time that Bradley, Mas- 

 kelyne, and Pond were the Astronomers Royal. 2 These Planetary ob- 

 servations were deduced, and the observed places were compared with 

 the tabular places : with Lindenau's Tables of Mercury, Venus, and 

 Mars ; and with Bouvard's Tables of Jupiter, Saturn, and Uranus ; and 

 thus, while the received theory and its elements were confirmed, the 

 means of testing any improvement which may hereafter be proposed, 

 either in the form of the theoretical results or in the constant ele- 

 ments which they involved, was placed within the reach of the astron- 



2 The observations of stars made by Bradley, who preceded Maskelyne at Green- 

 wich, had already been discussed by Bessel, a great German astronomer; and the 

 re?lts published in 1818, with a title that well showed the estimation in which he 

 held those materials : Fundamental Astronomia pro anno 1775, deducta ex Olserra- 

 tionibus viri incomparaUUs James Bradley in specula Astronomica Gnnoi'icensi p<-t 

 annos 1750-1762 instltutis. 



