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 Geographical Society of Australasia A. A. Simpson (president 1925–1930), John Lewis (president 1913–1920) and Clive M. Hambidge (president 1944–1947). Royal Geographical Society of Australasia On 22 June 1883, the Geographical Society of Australasia started at a meeting in Sydney. A branch was formed in Victoria in the same year. In July 1885, both the Queensland and the South Australian branches started. In July 1886 the society became the Royal Geographical Society of Australasia. The New South Wales branch's new constitution in 1886 widened its scope to encourage interest in scientific, commercial, educational and historical aspects of geography. The Society sponsored several important expeditions, notably