Franklin , Benjamin

(1706–1790) American scientist, statesman, diplomat, printer, and inventor

Franklin's father left England in 1682 and the following year settled in Boston, Massachusetts, where he worked as a candle maker and soap boiler. Although originally intended for the clergy, Franklin, who was born in Boston, was forced to leave school at the age of ten for financial reasons; after helping his father for some time he was apprenticed to his brother, a printer, in 1718.

He continued his trade as a printer in London (1724–26), and thereafter in Philadelphia where he published, from 1729, thePennsylvania Gazette and, from 1733, the hugely successful Poor Richard's Almanac. Shortly afterward Franklin began his life in public affairs serving as clerk of the State Assembly (1736–51) and as deputy postmaster representing the colonies (1753–74), during which he saw further service in London (1757–62; 1764–75). On his return to America Franklin played an active role in the revolution and was one of the five who drafted the Declaration of Independence in 1776. He was sent to France in 1776 to seek military and financial aid for the colonies and largely through his own popularity succeeded in achieving an alliance in 1778. Returning to America in 1785, he performed his last public duty as a member of the Constitution Convention in 1787 before retiring from public life in 1788.

Despite such an active political and public life Franklin also made important contributions to 18th-century physical theory in the period 1743–52. By conversation with scholars in London, reading, and correspondence with friends, his interest in the newly discovered phenomena of electricity had been aroused.

Franklin would have known of the work of Stephen Gray and Charles Dufay and the basic distinction established between electrics (such as glass and amber), which could be electrified by rubbing, and nonelectrics (such as metals), which resisted such treatment. Electrics were further divided into vitreous substances, such as glass, and resinous substances, such as amber. Dufay had concluded that there were two distinct electric fluids – the vitreous and the resinous – in his two-fluid theory.

Franklin agreed with Dufay that electricity was a fluid. More significant properties of electricity emerged out of Franklin's experiments from 1747 onward. From these experiments, including those on the Leyden jar, Franklin devised his one-fluid theory of electricity. He also introduced the terminology of ‘positive’ and ‘negative’ into the science.

Practical gains emerged from Franklin's discovery that lightning is an electric charge. He knew that the electric fluid was attracted by points but wondered if lightning would also be attracted. In 1752 he performed his famous, yet hazardous, experiment with a kite during a thunderstorm and established the identity of lightning with electricity. Following this he suggested the use of lightning rods on tall buildings to conduct electricity away from the building and direct to ground.

Franklin also published works on the problems of light, heat, and dynamics. Outside of physics Franklin's most important scientific work was in oceanography with his study of the Gulf Stream. He measured its temperature at different places and depths, estimated the current's velocity, and analyzed its effects on the weather. From reports supplied to him by Nantucket sea captains he also constructed the first printed chart of the Gulf Stream. Franklin is also remembered for his large number of inventions that included (in addition to his lightning rod) bifocal spectacles, the rocking chair, and an efficient stove.