DANIELL, JOHN FREDERIC

born March 12, 1790, London died March 13, 1845, London British chemist and meteorologist who invented the Daniell cell, which was a great improvement over the voltaic cell used in the early days of battery development. In 1820 Daniell invented a dew-point hygrometer (a device that indicates atmospheric humidity), which came into widespread use. In his Meteorological Essays and Observations (1823), Daniell revealed his findings on the behaviour of the atmosphere and on trade winds, in addition to giving details of improved meteorological equipment. In a later edition he also discussed the meteorological effects of solar radiation and the cooling of the Earth. Daniell's Essay on Artificial Climate Considered in Its Applications to Horticulture showed the importance of humidity in greenhouses. In 1831 he became the first professor of chemistry at the newly founded King's College in London. One year later, for his invention of a new pyrometer (a heat-measuring device) and for his papers detailing uses for the pyrometer, Daniell received the Rumford Medal of the Royal Society. The voltaic cell, though important as the first source of continuous electricity, is of limited use because it begins losing power rapidly as current is drawn. In 1836 Daniell proposed an improved electric cell that supplied an even current during continuous operation. The Daniell cell gave new impetus to electric research and found many commercial applications. In 1837 Daniell was presented the highest award of the Royal Society, the Copley Medal, for the invention of the Daniell cell.