In The Stones of Venice England's leading art critic, John Ruskin (-), made explicit the importance of geological knowledge for architecture. Clearly an architect's choice of stone was central to the character of a building, but Ruskin used the physical composition of rock to help define the nature of the Gothic style. He invoked a powerful geological analogy which he believed would have resonance with his readers, explaining how the Gothic 'character' could be submitted to analysis, 'just as the rough mineral is submitted to that of the chemist'. 1 Like geological minerals, he asserted that the Gothic was not pure, but composed of several elements. Elaborating on this chemical analogy, he remarked that, 'in defining a mineral by its constituent parts, it is not one nor another of them, that can make up the mineral, but the union of all: for instance, it is neither in charcoal, nor in oxygen, nor in lime, that there is the making of chalk, but in the combination of all three'. 2 He concluded that the same was true for Gothic: the style was a union of specific elements, such as naturalism (the love of nature) and grotesqueness (the use of disturbing imagination). 3 His analogy between moral elements in architecture and chemical elements in geology was not, however, just rhetorical. His choice to use geology in connection with architecture was part of a growing consensus that the two disciplines were fundamentally linked.In early Victorian Britain, the study of geology invoked radically new ways of conceptualising the earth's history. Charles Lyell (-), in his Principles of Geology (-), had argued that the earth's form was best examined by studying geological activity, such as volcanoes, earthquakes and erosion. 4 Others, such as the Oxford cleric and geologist William Buckland (-), rejected this emphasis on examining natural phenomena, and instead promoted geology as a subject best studied through fossil collecting and the observation of the earth's strata layout. 5 Despite these differences over what was the correct approach to investigate geology, the investigation of the earth was becoming increasingly intimate with the construction of architecture. Geology involved new ways of analysing the composition of stone, and changing perceptions of how various rock types Architectural History (), -.