Humphry Davy (1778-1829), English chemist. Davy is best known for his invention of the miner's safety lamp, also known as the Davy lamp, which could be used in gassy coal mines. In 1807 & 1808, Davy discovered the elements potassium, sodium, calcium, barium, magnesium and strontium. He did this by driving an electric current into molten solutions, a technique known as electrolysis. 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.