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 Tasmania having had a continuing existence since 1843. Earlier bodies include the 1837 formation of the Tasmanian Society of Natural History by Sir John Franklin assisted by Ronald Campbell Gunn. Queen Victoria became Patron of the Botanical and Horticultural Society of Van Diemen’s Land in 1844 and the name was changed to The Royal Society of Tasmania of Van Diemen’s Land for Horticulture, Botany and the Advancement of Science. Under the current Act of Parliament, passed in 1911, the name was shortened to The Royal Society of Tasmania. On the event of the sesquicentenary of the Society in 1993 it produced