The letters in this volume cover Poincaré's multifaceted career in astronomy in its entirety, extending from the time of his first publications in 1880 to the end of his life in 1912. At a tender age, Poincaré established his authority in questions of celestial mechanics, and his views were soon sought after on a vast array of questions by the leading astronomers and geodesists of his time, including C.V.L. Charlier, G.H. Darwin, H. Faye, F.R. Helmert, G. W. Hill, A. Lindstedt, A.M. Liapunov, N. Lockyer, S. Newcomb, K. Schwarzschild, and F. Tisserand. Poincaré and his correspondents take up topics ranging ... Read morefrom the three-body problem and perturbation theory to the determination of the geoide and the equilibrium figures of rotating fluid masses. The volume also sheds light on Poincaré's three terms as president of the Bureau of Longitudes, where he guided French astronomy and geodesy through ambitious projects, such as the measurement of an arc of meridian near Quito.

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Les lettres du troisième volume de la Correspondance de Poincaré scandent toute son œuvre astronomique, allant de ses premiers mémoires sur les courbes définies par une équation différentielle (1881), jusqu'aux analyses des hypothèses cosmogoniques (1911). Encore très jeune, Poincaré s'est fait remarquer pour sa maîtrise des questions de la mécanique céleste, de tel sorte que les astronomes et les géodésiens l'ont souvent interpellé, y compris O. Callandreau, C.V.L. Charlier, G.H. Darwin, F.R. Helmert, A. Lindstedt, A.M. Lyapunov, Simon Newcomb, Karl Schwarzschild et F. Tisserand.