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APPENDIX. 



de Motuum Coelestium Causis.&quot; As these tracts coincide 

 in their subjects and in many of their doctrines with the 

 propositions of Sir I. Newton, it has been held by some, 

 and apparently by Sir Isaac himself, that their author 

 had obtained from those propositions the substance at 

 least of his own. This is certainly a grave charge against 

 Leibnitz ; inasmuch as he affirms that he had not seen 

 the Principia when he wrote his two papers, admits that 

 he had seen an abridgment of it in general terms, and 

 expresses regret at not having seen the work itself. He 

 further states his inability to comprehend by what me 

 thods the most important of Newton s discoveries, as de 

 scribed in the abridgment, the elliptical motion of the 

 heavenly bodies, is demonstrated mathematically from 

 the data obtained by observation, and the law of attrac 

 tion governing that motion ; a proposition which Leibnitz 

 gives as deduced by himself with the aid only of the 

 differential calculus. The whole statement, though not 

 in direct terms, yet by manifest implication, represents that 

 he had made his investigation, and arrived at the result, 

 without any further knowledge of the Principia than the 

 fact of Sir I. Newton having obtained the same result 

 by his process, whatever it might be. 



It cannot be denied, therefore, that the strongest proof 

 is required to authorise the belief of his having seen the 

 Principia, and borrowed his propositions from thence. But 

 instead of proofs there appear to exist only certain sus 

 picious circumstances. His statement (Act. Erud. 1689, 

 January, p. 36.) is perhaps too particular in describing 

 his absence from home on his official journey. Newton 

 says that a copy of the Principia had been given imme 

 diately after its publication, to Facio Duiller, a young 

 mathematician, a friend of Huygens and of his own, for 

 the purpose of its being sent to Leibnitz ; but there is no 

 evidence that it reached him. (Macclesfield MS. Paper 

 in Newton s handwriting. Rigaud s Historical Essay, 

 App. Nos. XIX. XX.) The same paper of Newton 



