Inventor, Lexicographer. He was the creator of the first "Thesaurus," a book that lists words in groups of synonyms and related concepts. The original purpose of this publication was to facilitate authors, who were searching for words. His "Thesaurus of English Words and Phrases" was published in 1852, has never been out of print, and at the book's 150th anniversary in 2002, had sold 32 million copies. Born the son of a Swiss cleric, Jean Roget, he was of French Huguenot ancestry. His father died of tuberculosis in 1738, and his widowed mother, Catherine Romilly, the daughter of a wealthy jeweler, moved several times before settling in Edinburgh. His uncle was Sir Samuel Romilly, a successful politician known for prison sentencing reforms. Starting at age 14, he studied medicine at the University of Edinburgh, graduating in 1798. He was considered a "gifted" student, who was known for having an obsession with making lists to keep an organized system in his life. This included making a list of words with the same or similar meanings. During a tour of Europe in 1802, he was imprisoned for two months because he was an Englishman in Napoleon's France. He moved to London in 1808 and in 1809 became a licentiate of the Royal College of Physicians yet never had a large medical practice. He was a private teacher of mathematics and anatomy. In 1814, he invented the "log-log," a type of slide rule for calculating the roots and powers of numbers. From 1815 to 1817 he wrote medical articles for the "Encyclopedia Britannica." In 1824 he presented a paper to the Royal Society about a peculiar optical illusion, which was described as the phenomenon of "persistence of vision," establishing the theoretical prototype of the modern movie camera. He also improved the kaleidoscope. On March 16, 1815, he became a fellow of the Royal Society, and later from 1827 to 1848, he was Secretary of the Royal Society. In 1821 he became a Fellow of the Royal College of Physicians. A prolific writer, he authored papers on tuberculosis, various medical issues concerning prison inmates, London's water supply, and various disorders affecting the nervous system. In 1834 he published his two-volume text "Animal and Vegetable Physiology Considered with Reference to Natural Theology" for "Bridgewater Treatises." In 1834 he became the first Fullerian Professor of Physiology at the Royal Institution, helped found the medical school at Manchester, and helped found the University of London in 1837. After ending his medical practice in 1840, he focused on the study of languages and other interests. He published a 50-page article "Galvanism" in the "Encyclopedia Metropolitan" in 1845. In 1824 he married Mary Taylor Hobson, a French Huguenot, and the couple had a son and a daughter. His son, John Lewis Roget, became a well-respected artist with his work on display at the British Museum and revised and expanded the "Thesaurus," as well as his grandson Samuel Romilly Roget in 1950. After his wife died in 1833 of cancer, he became deaf and his unmarried daughter became his caregiver. While on vacation in Worcestershire with his daughter, he died during a heatwave and was buried there. His daughter, Kate, shares his marker. In honor of him, he has a University of Edinburgh plaque erected in George Square in Edinburgh.