George Julius Poulett Scrope (1797–1876) published Considerations on Volcanos in 1825. The work contains the results of his observations of volcanos in the volcanic regions of central France, Italy and Germany. It includes scientific descriptions of all volcanos in these areas, with each categorised according to its level of activity, main characteristics and geological history. Scope's work was one of the first attempts at a comprehensive theory of volcanic action and an understanding of the significance of volcanos as evidence for the earth's history. Scrope argued that volcanos should be studied in terms of known geological processes, and that 'non-catastrophic' causes should be considered to explain their formation. He argued that a gradual cooling of the earth was key to the formation of volcanos. This is a major work of nineteenth-century geology that sets out many of the principles still followed in vulcanology.