Henry Cavendish (October 10, 1731—February 24, 1810) was a British natural philosopher, but he is best known for his work in experimental and theoretical chemistry and physics during the 18th century. His research was based on the composition of atmospheric air, the properties of different gases, the synthesis of water, and a mechanical theory of heat. His experiment to calculate the density of the Earth is named after him and is known as the Cavendish experiment.