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