Electric light be made with a screw-thread base, two metal pins, two metal caps or a bayonet cap. The three main categories of electric lights are incandescent lamps, which produce light by a filament heated white-hot by electric current, gas-discharge lamps, which produce light by means of an electric arc through a gas, and LED lamps, which produce light by a flow of electrons across a band gap in a semiconductor. Before electric lighting became common in the early 20th century, people used candles, gas lights, oil lamps, and fires. Cornish chemist Humphry Davy developed the first incandescent light in 1802, followed
Royal Society of Edinburgh Royal Society of Edinburgh or the Royal Society of London. Presidents of the Royal Society of Edinburgh have included: The Society traditionally has more than one Vice President at any given time. Vice Presidents of the Royal Society of Edinburgh have included: Royal Society of Edinburgh The Royal Society of Edinburgh is Scotland's national academy of science and letters. It is a registered charity, operating on a wholly independent and non-party-political basis and providing public benefit throughout Scotland. It was established in 1783. , it has more than 1,660 Fellows. The Society covers a broader selection of fields than the