NEWTON S PRINCIPIA. 97 



ample justice to Newton s transcendent merits in other 

 respects. But here Bailly has a far higher authority than 

 his own against him, justly as his own name is held in 

 respect. Laplace, in his earlier writings*, had seemed 

 not sufficiently impressed with the inestimable value of 

 that part of the Principia; and had, while he distinctly 

 gave the work at large the f pre-eminence over all other 

 productions of the human understanding,&quot; yet appeared 

 to regard the theory of disturbed planetary motion, and 

 especially of the moon s motion, as a sketch left for others 

 to complete when the calculus should be more improved. 

 Yet in his last work, the concluding part of the Me- 

 canique Celeste, published the year before his death, he 

 distinctly declares this very portion of the Principia to 

 be among the greatest monuments of the author s genius. 

 &quot; Je n hesite point a les regarder (recherches sur la theorie 

 de la lune) comme une des parties les plus profondes 

 de cet admirable ouvrage.&quot;f 



It remains, however, that we mention an unaccountable 

 statement of the truly great geometrician whom we have 

 last cited. In treating of the history of the lunar theory, 

 he says that Newton, when seeking the correction of the 

 sun s disturbance of the moon s gravitation towards the 

 earth, &quot; supposes that disturbance to be 3 1 7 of the moon s 

 gravity, or that which results from the observed amount of 

 the lunar apogee.&quot; (Mec. Cel. lib. xv. chap. 1.) For this 

 he refers to Book iii. Prop. iv. of the Principia, which is 

 evidently a wrong reference, that proposition, and indeed 

 that part of the book, treating of other subjects. Nor can 

 any place be found that Laplace could have had in his 

 view, except the Twenty-first proposition of the Third 



* Systeme dn Monde, liv. v. chap. 5. 

 f Mt-c. Ccl. liv. xvi. chap. 1. ; published in 1825. 

 II 



