Engraving of the English chemist Sir Humphrey Davy by J. Thomson after a painting by H. Howard, c 1822. Humphry Davy (December 17, 1778 - May 29, 1829) is best known for his invention of the miner's safety lamp, also known as the Davy lamp, 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 anesthetic.