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
Thomas Graves (1802–1856) died in Malta on 28 August 1856, from a wound inflicted by Maltese boatman Giuseppe Meli. Meli was later tried for Graves's murder. Thomas Graves R.N. was a Member of the Belfast Natural History Society and an Associate Royal Geographical Society. Thomas Graves (1802–1856) Thomas Graves (1802 – 28 August 1856) was an officer of the Royal Navy and naturalist who worked extensively in the Mediterranean. Thomas Graves was born in Belfast in 1802 and entered the Navy in 1816. In 1827 he was promoted to lieutenant in HMS "Adventure", under the command of Philip Parker King and surveying on