1900 – “Celestial Mechanics and the New Century” – Palais des Sciences, Paris
1901 – “Observations of the Transit of Mercury” – Observatoire de Lyon
1903 – “Stellar Photography: Capturing the Night Sky” – Société Astronomique de France, Paris
1904 – “The Moons of Jupiter: A Photographic Study” – Institut de France
1906 – “Cometary Orbits and Celestial Prediction” – Académie des Sciences, Paris
1907 – “Solar Eclipse Observations from Algeria” – Musée d’Histoire Naturelle, Paris
1909 – “Variable Stars of the Southern Hemisphere” – Observatoire de Nice
1911 – “Nebulae Classifications: New Discoveries” – Royal Astronomical Society, London
1912 – “Asteroid Belt Mapping Project” – Sorbonne, Paris
1914 – “War Time Astronomy: Maintaining Science” – Observatoire de Strasbourg
1916 – “Double Star Systems and Orbital Mechanics” – Académie de Bordeaux
1918 – “Post-War Astronomical Reconstruction” – Observatoire de Paris
1920 – “Einstein’s Relativity and Stellar Observations” – École Normale Supérieure
1922 – “The Great Andromeda Nebula Controversy” – Institut Astrophysique, Paris
1924 – “Planetary Atmospheres: Spectroscopic Analysis” – Observatoire de Meudon
1926 – “Twenty-Five Years of Celestial Photography” – Galerie Scientifique, Paris
1928 – “The Expanding Universe: New Evidence” – Collège de France
1930 – “Search for Trans-Neptunian Objects” – Observatoire de Toulouse
1931 – “Radio Waves from Space: A New Frontier” – Institut de Physique, Paris
1932 – “A Career in Astronomy: Retrospective Exhibition” – Musée des Arts et Métiers, Paris