Six's self-registering thermometer by Cary, 18th century.
© Science Museum / Science & Society Picture Library
James Six (1731-1793) retired early from business to devote himself to the natural sciences. He is best known for the invention of the self-registering thermometer, first designed in 1780, which recorded the maximum and minimum temperatures reached. It was the most widely used thermometer for taking deep-sea temperatures until 1870.