Leonard Horner (1785–1864) was a prominent geologist, educator and, later, a factory inspector. In 1833 he was appointed to the Royal Commission on the employment of children in factories, and he inspected sites around the north of England. His earlier scientific work saw him elected a fellow of the Royal Society in 1813, and he was twice president of the Geological Society. The two-volume Memoir of Leonard Horner, edited by his daughter, Katharine Lyell, and published in 1890, is a selection of letters to and from his family and friends. The correspondence gives vivid insights into the world of this influential reformer, his scientific, social and political concerns, and key moments in his personal life.