Social reformer and geologist. Born in George Square in Edinburgh, the younger brother of Francis Horner (1778 - 1817), and educated at the University, Horner joined the family business and moved to London (1804). There he was able to indulge his interests in mineralogy and became a founder of the Geological Society of London.
On his return to Edinburgh, he set about trying to improve conditions for the working classes, and to this end founded the School of Arts (1821) one of the first institutions specifically for the technical education of tradesmen. Through funds raised in the memory of James Watt (1736 - 1819), the school was able to obtain new premises (1852), merged with George Heriot's Hospital (1885) and eventually developed into Edinburgh's Heriot-Watt University (1966).