Cloud types, 19th century artwork. At lower left is a cumulonimbus cloud, a storm cloud that has developed vertically to form an anvil-shaped thunderhead. Above it to its right is a cumulus cloud. Directly above the cumulonimbus clouds are altocumulus and then cirrocumulus clouds. At top are cirrus clouds. Artwork from 'A Treatise on Meteorology: With a Collection of Meteorological Tables' (1868) by the American mathematician Elias Loomis (1811-1889).