The first facts about the Earth were worked out by the Ancient Greeks. A good estimate of the Earth's size was made by Eratosthenes (276 –194 ), using trigonometry. The first estimate of the Earth's age based on evidence was by Benoît de Maillet (1656–1738), a French diplomat, philosopher and naturalist. He thought the Earth must have developed by slow, natural forces. He studied geology in the field. He could see signs of erosion on land and sedimentation in the sea. He hid his ideas under the guise of a talk with an Indian philosopher, to avoid conflict with the Catholic Church. His work stayed in manuscript until after his death, when it was published after its editor had made changes which damaged it. Now there is a better modern edition based on the manuscripts. de Maillet estimated that the Earth was older than two billion years. He also recognized the true nature of fossils, and had early ideas about evolution.