Sir Humphry Davy, Cornish chemist and physicist, (20th century). Davy (1778-1829) discovered the anaesthetic effects of laughing gas (nitrous oxide). In 1801 he was appointed lecturer at the Royal Institution, where he investigated, with his assistant Michael Faraday (1791-1867), his theory of volcanic action. Using electrolysis, Davy isolated the metals barium, calcium, magnesium, potassium, sodium and strontium, as well as proving that chlorine was a chemical element. He is probably best known for his invention in 1815 of the miners' safety lamp, which enabled deeper, more gaseous seams to be mined without risk of explosion.