The second type, metaphysical-mystical, involved looking up to the heavens rather than down to the things of this world. Rousseau tended to embark on this kind of walk at night: “Soon I lifted up my ideas from the surface of the earth to all the beings of nature, to the universal system of things ... With a sort of pleasure I felt overwhelmed by the weight of the universe; with delight I gave myself up to the confusion of these great ideas; in imagination I loved to lose myself in space.”

For the Lakeland poets, Wordsworth and Coleridge, perambulation through stretches of untamed nature was a necessary prelude to the composition of verse. William Hazlitt, who knew both men, believed that Wordsworth’s insistent sense of meter and Coleridge’s speculative, gadfly intellect were reflected in their very ways of walking: “Coleridge has told me that he himself liked to compose in walking over uneven ground, or breaking through the straggling branches of a copse-wood; whereas Wordsworth always wrote (if he could) walking up and down a straight gravel-walk, or in some spot where the continuity of his verse met with no collateral interruption.”

The ramblings of the Romantics lead circuitously but surely to the walks and works of Richard Long, a retrospective of whose perambulatory art has just opened at Tate Britain. Long calls himself a sculptor, but his reveries of a solitary walker range at will across many genres. Some of his works take the form of lists of objects seen or experiences undergone. Presented as words on paper or, sometimes, stencilled to a wall, they bear laconic witness to rituals performed in the name of self-enlightenment or sometimes, simply, self-annihilation in nature. On a twenty-one day walk in Nepal, the artist notes, for example, “Starlit Snow”, “Frozen Boots”, “Circles of a Great Bird”. Like Rousseau, he seeks out the solitary corners of the world, and is just as liable to think cosmic as he is to get lost in the microcosms of stone, shell and flower. In some of his word-walks, he notes not only the distance he himself has travelled in a day or a week, but the distance the earth has travelled too.

Other works are things made outdoors then preserved as photographs. Long might make an ephemeral painting by splashing water on a rock somewhere in the Avon Gorge; or he might make a sculpture by erecting a line of standing stones in an Andean wilderness. The work is a fleeting intervention, designed to disappear back into the natural flux from which it was originally conjured. The artist’s ethic is that of the nomad, who works within the rhythms of the landscape, moving through and leaving as is, rather than of the settler, who wants to own and thus enact a permanent transformation on a particular part of the face of the globe. Implicit in almost all that he does is a literal desire to save (or at least preserve) the world.

Two of the points joined up by Long’s many acts of walking are modern environmentalism and its origins in Romantic nature worship, which was sparked in no small part by the advent of the modern metropolis and modern forms of heavy industry. Always implicit in the Romantic rapture before nature was the fear that it might disappear.

Long, now in his mid-sixties, is the knowing heir of that tradition of anxious love. One of his very earliest walks/works, created in 1967, was simply entitled A Line Made by Walking. It consists of no more than a simply framed black-and-white photograph of a field somewhere in the English countryside. Across the grass and daisies, Long has trodden a single, straight, impeccably Wordsworthian line, pacing up and down so many times that he has left the trace of his own passage. The very first “walking sculpture” is a dream of disappearing into nature, being swallowed up by the greensward.

The sources for Long’s work are not only western but also eastern. Many of his gallery-based sculptures, circles of rock or stone, fields of marble chippings, seem inspired by the same Buddhist aesthetic as the great Japanese rock garden at Kyoto. But the western love of eastern mysticism might itself be said to have its roots in the Romantic movement, coloured as it was by a strong vein of orientalism.

There was always something priestly,  sacerdotal, about the Enlightenment fantasy of a return to nature. Over the years, Long’s sense of himself as a priest or shaman has undoubtedly grown. He plays with river mud with ever-increasing abandon, smothering walls with gestural fields of form that he himself compares to the ancient mark-making of cavemen. Other works demonstrate that he is not quite (certainly not always) the faux-naif primitivist suggested by such daubings. “Windmill Hill to Coalbrookdale” is a word-and-photograph piece documenting Long’s walk from the site of England’s earliest known human intervention in the landscape – a small, dimpled, circular protuberance in Shropshire – to the birthplace of the Industrial Revolution. The solitary walker dreams of being a primitive but knows that it is only a dream, at the same time. He travels to the furthest places to escape. He runs away to Canadian prairie, Bolivian wilderness, Norwegian wasteland. But he knows he cannot really escape and he bears within himself a sense of guilty complicity in the forging of the modern world.