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 Scottish Society of Painters in Watercolour Barbara Rae. Past presidents include William J L Baillie (1975–1988), Ian McKenzie Smith (1988–1998), Philip T L Reeves (1998–2005), John Inglis (2005–2016); the current president is Jim Dunbar. Past vice presidents include Alison Dunlop, Helga Chart, Gregor Smith and Iona Montgomery. Royal Scottish Society of Painters in Watercolour The Royal Scottish Society of Painters in Watercolours (RSW) is a Scottish organisation of painters. It was founded in 1876, with the support of the Royal Scottish Academy, by artists to "promote, through exhibition, the medium of watercolour and encourage the bold, free and colourful qualities of Scottish Painting." The society received