NEWTON S PRINCIPIA. 95 



be mentioned, that the statement made by Bailly is even 

 more incorrect upon this subject of the moon s apsides than 

 upon the motion of the planetary axis. He asserts that 

 Newton represented the theory as ( giving the quantity 

 of the moon s apogeal motion with exactness ; &quot; and that 

 this having been a mere dictum of his without a demon 

 stration, philosophers waited to find it proved by subse 

 quent inquiry, as the theory had been on so many other 

 points. The great inaccuracy of the substance is assuredly 

 not rendered the less distasteful by the manner of this 

 statement. &quot; II avait souvent parle a la maniere des pro- 

 phetes qui disent ce qu on ne peut voir : alors c est la foi 

 qui croit, il faut que la raison se soumette.&quot; (Hist, de 

 TAstron. iii. 150.) Newton never asserts anything which 

 may not, from what he himself lays down, be strictly 

 demonstrated. He certainly leaves much to be supplied ; 

 but he never leaves the reader who would, with due know 

 ledge of the mathematics, follow his reasoning, to trust 

 his word. Even the scholium at the close of the Lunar 

 theory (after Proposition xxxv. B. iii.), where more of 

 the investigation is omitted than perhaps in all the rest of 

 the Principia together, may be followed argumentatively 

 by a learned and diligent reader, as the Jesuits have shown 

 in their inimitable commentary upon it. But touching 

 the particular instance referred to by Bailly, nothing can 

 be more contrary to the fact than his statement. Sir 

 Isaac Newton in the general proposition which we have ana 

 lysed above, after finding that any body acted upon by a 

 disturbing force in the given proportion to the centripetal, 

 will have by the theory a progressive motion of its apsides 

 equal to 1 31 28&quot;, although he had not in the whole 



as having been undertaken by them and Euler at the same time. See 

 Life of D Alembert, p. 427., where the history of this celebrated investigation 

 is given at length. 



