"The phenomenon develops calmly, but it is invisible, unstoppable. One feels, one sees it born and grow steadily; and it is not in one's power to either hasten it or slow it down. Any person, brought into the presence of this fact, stops for a few moments and remains pensive and silent; and then generally leaves, carrying with him forever a sharper, keener sense of our incessant motion through space."

“You are invited to come to see the Earth turn, tomorrow, from three to five, at Meridian Hall of the Paris Observatory.”

“Above all, we must be accurate, and it is an obligation which we intend to fulfil scrupulously.”

“May those men who are animated by the true scientific spirit cease to believe that they are obliged to consider only subjects of public utility; ...because, one must not hide it, the field of applications, so rich and fertile today, would not take long to be blighted by sterility if it ceased to be fertilized and revivified by the beneficial light which theoretical research radiates and pours incessantly upon it.”

“To contribute usefully to the advance of science, one must sometimes not disdain from undertaking simple verifications.”