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
Philosophical Transactions of the Royal Society to access without a login. Philosophical Transactions of the Royal Society Philosophical Transactions, titled Philosophical Transactions of the Royal Society (often abbreviated as Phil. Trans.) from 1776, is a scientific journal published by the Royal Society. In its earliest days, it was a private venture of the Royal Society's secretary. It became an official society publication in 1752. It was established in 1665, making it the first journal in the world exclusively devoted to science, and therefore also the world's longest-running scientific journal. The use of the word "philosophical" in the title refers to natural philosophy, which was the equivalent