John Dalton was a renowned British chemist, best remembered for introducing atomic theory into chemistry. This is the theory that all substances are made from tiny particles called atoms. His theory revolutionised scientific understanding, helping to explain chemical phenomena that had long puzzled scientists, and providing a theoretical foundation for chemistry that remains today.
James Joule became a world-renowned physicist, initially by seeking scientific advances to help his family brewery. He is best remembered for his discovery that different forms of energy - electrical, mechanical, heat - are interchangeable, and for establishing that energy can neither be created nor destroyed. The International unit of energy, the joule, is named in his honour.