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 the foundation of the modern sciences. From the 20th century onward, the society functioned not only as a focal point for Scotland's eminent scientists, but also the arts and humanities. It still exists today and continues to promote original research in Scotland. In February 2014, Dame Jocelyn Bell Burnell was announced as the society's first female president, taking up her position in October. The Royal Society has been housed in a succession of locations: Fellowship of the Royal Society of Edinburgh is an award in its own right that entitles fellows to use of the initialism or post-nominal letters FRSE