D'ALEMBERT, 425 



distance of that body from each of the two others, and 

 the almost elliptical path of the one whose orbit was 

 sought, leaving its deviation from that path alone to be 

 sought after. Accordingly, the paper of 1743 did not 

 satisfy its illustrious author, who, in 1747, produced 

 another worthy of the subject and of himself. This was 

 read 15th November, 1747, but part of it had been read 

 in August. He asserts positively in a note ('Mem./ 1745, 

 p. 335,) that though Euler's first paper had been sent in 

 the same year, he had never seen it till after his solution 

 was obtained; therefore, Lalande had no right to state 

 in his note to the very bad edition of Montucla which 

 he published, wholly incapable of the task, that Fon- 

 taine always said that Clairaut was enabled to obtain his 

 solution by the paper of Euler, (Vol. iv. p. 66.) 



At the time that Clairaut was engaged in this 

 investigation, D' Alembert, unknown to him, was working 

 upon the same subject. Their papers were presented on 

 the same day, and Clairaut's solution was unknown to 

 D' Alembert ; but so neither could D'Aleinbert's solution 

 have been known to Clairaut, because the paper is 

 general on the problem, and the section applicable to the 

 moon's orbit was added after the rest was first read, and 

 was never read at all to the Academy. Nothing, there- 

 fore, can be more clear than that neither of these great 

 geometricians borrowed from the other, or from Euler. 

 It is just possible that Euler in his complete solution 

 of 1752 might have had the advantage of their pre- 

 vious ones; but as it clearly flowed from his earlier 

 paper, there is no doubt also of his entire originality. 

 Nevertheless, when D' Alembert 's name became mixed 

 up with the party proceedings among the literary and 



