The period between 1790 and 1820 saw striking changes in the depiction of British landscape. Conventional pictorial formulae (the sublime, the beautiful, and the picturesque) were abandoned in favour of what has been called a more 'naturalistic' mode of representation. The thesis argues that this is not the outcome of a logic internal to art alone, but best understood as interwoven with changes in the understanding of nature taking place more broadly at this time, in particular, in contemporary science. The first chapter links eighteenth-century aesthetic theories to contemporary physiological and philosophical investigations. Around the turn of the century a new understanding of the relationship between the mind and the world, based on a new conception of causality, replaced the eighteenth-century belief in a unifying common medium in all three fields. The second chapter focuses on one particular project in which art and science were consciously brought together under the auspices of a unitary metaphysics: Robert J. Thornton's botanical treatise The Temple of Flora. Its failure indicates that such enterprises were coming to seem increasingly fanciful. The third chapter counterposes geological treatises and their illustrations with contemporary landscape art. On the one hand, geological illustrations lagged behind the texts which they accompanied. On the other hand, the emergence of a new fieldwork approach in geology seems to have stimulated artists to perceive landscape .i,r.t ways that led beyond established formulae. The last chapter concentrates on the circle of artists around John and Cornelius Varley in London. It is argued that Cornelius Varley, who had serious scientific interests, was an important influence on the 'photographic' style of landscape depiction that developed within the circle. In conclusion, the traditional modes of landscape art were sustained by an epistemology which saw reality as mediated by a single, underlying common principle. As the credibility of such world-views came increasingly to be called into question, a subjectivistic approach, commonly termed 'naturalism' or 'empiricism', but which is better named phenomenalism, provided a short period of unstable synthesis at the beginning of the nineteenth century between the scientific observation of nature and the personal response of the perceiver.