Cloud atlas was published in 1802. It followed a similar effort in French by Jean-Baptiste Lamarck in 1801. Howard's nomenclature defined four fundamental types of clouds: cirrus or thread-cloud, cumulus or heap-cloud, stratus or flat cloud (level sheet), and nimbus or rain-cloud (see Classification of clouds). There followed a long period of development of the field of meteorology and the classification of clouds, leading up to 1896, the International Year of Clouds. The history of this period is the subject of a popular book, "The Invention of Clouds". During that time, the Englishmen Rev. Clement Ley and Hon. Ralph Abercromby, were influential.
Sheet erosion some limited unevenness in the sheet flow arising from clods of earth, rock fragments, or vegetation. Sheet erosion occurs in two steps; first rainsplash dislodges small particles of the substrate and then the particles are carried away, usually short distances, by a thin and uniform layer of water known as sheetflow. Transport by the sheetflow is usually small distances meaning sheet erosion is a low magnitude process. However the frequency in time with which the occur may be high, compensating for the small change observed in each individual episode of sheet erosion. A sheetflood can be distinguished from ordinary an