D'ALEMBEET. 467 



employment of it to arrange the whole of mechanical 

 science, exceeds anything accomplished by either of his 

 illustrious contemporaries in usefulness, indeed in origi- 

 nality ; while of a most important calculus he was, if not 

 the father, certainly the person who by applying it and 

 teaching its uses, almost changed the face of geometrical 

 and physical science. His investigation of the lunar 

 orbit, of the earth's figure, of the precession and the 

 nutation, would have entitled him to rank with Euler and 

 with Clairaut, and before Fontaine, had his ' Dynamique ' 

 and his ' Partial Differences ' * never been given to the 

 world. On the latter subject, Euler and Fontaine in 

 some sort anticipated him; but taking the former dis- 

 covery into our account, and his application of the cal- 

 culus, we shall probably be justified in placing him the 

 first among the philosophers and geometricians who 

 succeeded Sir Isaac Newton. 



It is equally clear that no comparisons can be insti- 

 tuted between him and that most illustrious of the 

 human race. The 'Principia' stands at an immeasurable 

 distance before the ' Dynamique ;' and the Calculus of 

 Partial Differences is but an improvement, though a very 

 great one, of the Method of Fluxions ; while the optical dis- 

 coveries of Newton have so little that can be compared 

 with them in the history we are contemplating, that 

 D'Alembert never could bring himself to take an interest 

 at all in experimental philosophy, much less to make 

 any discoveries for extending its bounds. Not only 

 was he without any pretension of this kind, but he was 



* It is in his two works on Fluids, and in his Memoirs on the 

 Winds and Vibrating Chords, that we find this method, and rather 

 used or applied than explained. 



o w o 



~J ti -f 



