Calcul des probabilites. Lecons professées pendant le deuxieme semestre 1893-1894
(french ed.: Gauthier-Villars, Paris, 1896)
at The Cornell Library Historical Mathematics Monographs
[historical.library.cornell.edu/cgi-bin/cul.math/docviewer?did=05200001&view=50&frames=0&seq=7]

La Science et l'hypothèse
(french)
at Project Gutenberg Europe
[pge.rastko.net/dirs/pge/pge05/100025/e100025.html]

La Science et l'hypothèse
(french)
at Abu
[abu.cnam.fr/cgi-bin/go?scihyp2]

Lecons de mecanique celeste professees a la Sorbonne (vols. I-III)
(french ed.: Gauthier-Villars, Paris, 1905, 1907, 1910)
at The Cornell Library Historical Mathematics Monographs
[historical.library.cornell.edu/cgi-bin/cul.math/docviewer?did=04450002&seq=7]
[historical.library.cornell.edu/cgi-bin/cul.math/docviewer?did=04270002&seq=7]
[historical.library.cornell.edu/cgi-bin/cul.math/docviewer?did=04330002&seq=7]

Sechs vorträge über ausgewählte gegenstände aus der reinen mathematik und mathematischen physik, auf einladung der Wolfskehl-kommission der Königlichen gesellschaft der wissenschaften gehalten zu Göttingen vom 22.-28. april 1909 (with preface and sixth lesson in french)
(german ed.: B.G. Teubner, Leipzig und Berlin, 1910)
at The Cornell Library Historical Mathematics Monographs
[historical.library.cornell.edu/cgi-bin/cul.math/docviewer?did=00200001&seq=5]

Theorie des tourbillons. Lecons professees pendant le deuxieme semestre 1891-92
(french ed.: G. Carré, Paris, 1893)
at The Cornell Library Historical Mathematics Monographs
[historical.library.cornell.edu/cgi-bin/cul.math/docviewer?did=01800002&seq=7]

Théorie du potentiel Newtonien. Leçons professés [à la Sorbonne] pendant le premier semestre 1894-1895
(french ed.: Gauthier-Villars, Paris, 1899)
at The Cornell Library Historical Mathematics Monographs
[historical.library.cornell.edu/cgi-bin/cul.math/docviewer?did=03230001&seq=5]