Stock Photo - Humphry Davy, English chemist, 1860. 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 wrote on the subject of agricultural chemistry, but 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. After a portrait by Sir Thomas Lawrence. From Chemistry by J Sheridan Muspratt. (London, 1860).