296 A Short History of Astronomy tea. xi. 



astronomical or otherwise. During the next few years he 

 made a number of contributions to mathematical physics, 

 as well as to the problem of three bodies ; and published 

 in 1749 his work on precession and nutation, already 

 referred to (chapter x., 215). From this time onwards 

 he began to give an increasing part of his energies to work 

 outside mathematics. For some years he collaborated 

 with Diderot in producing the famous French Encyclopaedia, 

 which began to appear in 1751, and exercised so great 

 an influence on contemporary political and philosophic 

 thought. D'Alembert wrote the introduction, which was 

 read to the Academic Franfaise* in 1754 on the occasion 

 of his admission to that distinguished body, as well as a 

 variety of scientific and other articles. In the later part 

 of his life, which ended in 1783, he wrote little on mathe- 

 matics, but published a number of books on philosophical, 

 literary, and political subjects ; t as secretary of the 

 Academy he also wrote obituary notices (eloges] of some 

 70 of its members. He was thus, in Carlyle's words, "of 

 great faculty, especially of great clearness and method; 

 famous in Mathematics ; no less so, to the wonder of some, 

 in the intellectual provinces of Literature." 



D'Alembert and Clairaut were great rivals, and almost 

 every work of the latter was severely criticised by the 

 former, while Clairaut retaliated though with much less 

 zeal and vehemence. The great popular reputation acquired 

 by Clairaut through his work on Halley's comet appears 

 to have particularly excited D'Alembert's jealousy. The 

 rivalry, though not a pleasant spectacle, was, however, use- 

 ful in leading to the detection and subsequent improvement 

 of various weak points in the work of each. In other 

 respects D'Alembert's personal characteristics appear to 

 have been extremely pleasant. He was always a poor 

 man, but nevertheless declined magnificent offers made to 

 him by both Catherine II. of Russia and Frederick the 



* This body, which is primarily literary, has to be distinguished 

 from the much less famous Paris Academy of Sciences, constantly 

 referred to (often simply as the Academy) in this chapter and the 

 preceding. 



f t E.g. Melanges de Philosophic, de FHistoire, et de Litte'ra'ure ; 

 Elements de Philosophic ; Sur la Destruction des Jesiiites. 



