Peter Mark Roget
Peter Mark Roget is the English physician who is now famous for his dictionary of synonyms, the Thesaurus of English Words and Phrases. During his career he was a doctor in Manchester, a professor of physiology at the Royal Institution, and the secretary of the Royal Society. He retired in 1848 and devoted himself to his dictionary of synonyms, based on notes he'd been compiling since early in his career. In 1852 he published his thesaurus, now commonly called Roget's Thesaurus, which has been in print ever since.
Roget had wide interests and an inquisitive mind. His accomplishments include the invention of a slide rule he called a "log-log," used for calculating number roots and squares. He is also sometimes credited with a role in the history of cinema, thanks to a paper he presented in 1824 titled "Explanation of an Optical Deception in the Appearance of the Spokes of a Wheel Seen Through Vertical Apertures." In it he reported his observations of an optical illusion he had witnessed as he saw moving carriage wheels through vertical blinds. Although he apparently didn't pursue this line of inquiry, others have credited him with first noting the phenomenon called "persistence of vision" -- in which still photographs seen in rapid succession give the illusion of movement -- which in turn led to the cinema.