Humphry Davy (1778-1829), British chemist. Davy invented a miner's safety lamp (1815) for use in coal mines. In 1807 and 1808, Davy discovered the elements potassium, sodium, calcium, barium, magnesium and strontium. Davy is also credited with the concept of allotropes, elements that are physically different due to their structural arrangements. He proposed that diamond was an allotrope of carbon. He also discovered nitrous oxide or laughing gas, which he suggested could be used as an anaesthetic. Artwork from 'Electricite' (1911) by Max de Nansouty, part of the 'Les merveilles de la science' series of 1867-1891 by Louis Figuier.