Black, known for his discovery of latent heat, specific heat and carbon dioxide, was an influential member of the Scottish enlightenment. Cullen (who had taught him) and Watt (a close collaborator) became lifelong friends — in Watt’s case, after their Glasgow days, mainly by correspondence. Smith (another friend for life), Hutton, Hume and Ferguson were among his clubbable Edinburgh circle; he was Hume’s doctor, and sold a house to Ferguson. With Smellie and his close friend Hutton, he was a regular at Monboddo’s weekly ‘learned dinners’. He entertained Franklin, taught Beddoes, and was present when Burns met Scott.