His father, John Horner, was a linen merchant in Edinburgh, and partner in the firm of Inglis & Horner. Leonard, the third and youngest son, attended the High School and entered the University of Edinburgh in 1799. There in the course of the next four years he studied chemistry and mineralogy, and gained a love of geology from Playfairs Illustrations of the Huttonian Theory. At the age of nineteen he became a partner in a branch of his father's business, and went to London.
Career
In 1808 he joined the newly formed Geological Society of London and two years later was elected one of the secretaries. Throughout his long life he was ardently devoted to the welfare of the society; he was elected president in 1846 and again in 1860. In 1811 he read his first paper On the Mineralogy of the Malvern Hills and subsequently communicated other papers on the Brine-springs at Droitwich, and the Geology of the S.W. part of Somersetshire. He was elected fellow of the Royal Society in 1813. In 1815 he returned to Edinburgh to take personal superintendence of his business, and while there he was instrumental in founding the Edinburgh School of Arts 101 the instruction of mechanics, and he was one of the founders of the Edinburgh Academy. In 1827 he was invited to London to become warden of London University, an office which he held for four years; he then resided at Bonn for two years and pursued the study of minerals and rocks, communicating to the Geological Society on his return a paper on the Geology of the Environs of Bonn, and another On the Quantity of Solid Matter suspended in the Water of the Rhine. In 1828 he returned to Edinburgh to take charge of his ailing father's company. In 1829, on the death of his father, he took full charge of the company, and continued in this role until 1833. In 1833 he was appointed one of the commissioners to inquire into the employment of children in the factories of Great Britain, and he was subsequently selected as one of the inspectors. He held this post for 26 years and during this time arguably did more to improve the working condition of women and children in the mills of north England than any other person in the 19th-century and for which he was praised by Karl Marx in Capital. In later years he devoted much attention to the geological history of the alluvial lands of Egypt; and in 1843 he published his Life of his brother Francis.
Family
Horner married Anna Susanna Lloyd, daughter of Gamaliel Lloyd. They had six daughters, who were all educated to a high standard for the age. The eldest sister, Mary Elizabeth, married Sir Charles Lyell, author of The Principles of Geology in 1832. Her younger sister Katharine married Lyell's younger brother Henry in 1848, and later edited The Life, Letters and Journals of Sir Charles Lyell. A third daughter, Frances, married Charles Bunbury, a noted paleobotanist. A fourth daughter, Leonora, married Georg Heinrich Pertz, a historian and archivist; one of their children was Dorothea Pertz and through this connection Horner was the step-great-great-grandfather of astronomer and astrophysicist Cecilia Payne-Gaposchkin. Two other daughters, Susan and Joanna, did not marry but were known in their day as the authors of a book on walking tours of Florence, Italy.
Freemasonry
He was Initiated into Scottish Freemasonry in 1803 in Lodge Canongate Kilwinning, No.2. He was also an honorary member of Lodge Kirknewton and Ratho, No.85, this also being conferred in 1803.
