Richard Long

Bristol City Museum and Art Gallery

To celebrate the re-opening of its 20th-Century British Art room after redecoration, Bristol's municipal art gallery has commissioned a new work by the city's most famous artist, and assembled a small exhibition of works on paper from the Anthony D'Offay gallery to complement it. The work in question, Delabole Bristol Slate Circle 1997, is exactly that, a medium-sized assembly of slate slabs from the Delabole quarry in Cornwall, laid out on the parquet floor of the gallery to form a circle whose red perimeter-markings are sometimes still visible in between the slabs.

So what do you say about it? Well, it's certainly attracting a lot of attention. Small children run headlong into the gallery only to stop and stare, as if confronting some alien form that has only just beamed down; museum attendants walk past tutting disapprovingly; Sunday afternoon browsers look down questioningly, consult the title and the laminated sheet of educational notes on the wall, and move on. Long's work is famously resistant to interpretation. It is what it is, and the slate circle is just that, a circle made of slates. It's also very beautiful and the satisfyingly thick, long slabs cover the ground with a pleasing inevitability, as if they simply fell into place.

The colour of the circle (state-grey?) is also stunningly effective within the rather dim, institutional setting of the Victorian gallery. From a distance, it's a black hole, seeming to absorb all the ambient light of the space; yet, close to, it's light and delicate and some of the slabs glint with the browny-yellow residue of oxidised minerals. Viewed from above, the circle is flat and monumental; from a low angle, it's as rugged and spiky as the stones of the Giant's Causeway that the text-piece on the wall behind, All Ireland Walk, refers to.

Apart from All Ireland Walk, the other four works on paper are being shown for the first time. The most intriguing is River Avon Mud Drawing, which is, of course, exactly that. "It is made by mud and water and gravity," Long told the Gallery's Curator of Fine Art, Sheena Stoddard, last week. "The paper is dipped into a bucket of muddy water and left to dry. Part of the intellectual excitement is that it is a drawing, but not actually made by my hand." It looks like an archeological find from the Euphrates, the dripping lines of mud on paper drying to the texture of slip on ceramic. The other text pieces are by-products of the artist's famous walks: Concentric Days traces the line of a walk in Scotland on to an Ordnance Survey map; A Circle of Middays records "a clockwise and meandering walk of 12 days, intersecting each day at midday with an imaginary circle 63 miles wide". Gobi Desert Circle is a photograph of a circle of stones made in Mongolia in 1996.

Though the works might resist interpretation, to always take them at their word is to risk solipsism, for each viewer has to bring something of themselves to bear on them, and while a circle might not have a beginning or an end, it has to have a context and a meaning. The beauty and purity we perceive in Long's work is partly a consequence of its marvellous way with the geometry of archetypal forms, and the poverty of means he uses to express them, but it's also our response to a language as freighted with symbolic references as the circle itself. The text pieces use the modernist typography and black and red colours of the British Constructivist publication Circle, and even recall Frank Pick's iconic London Underground map of the Thirties. The text of All Ireland Walk juxtaposes the "found" language of the walk itself - descriptions of weather, etc - with a poet's eye and ear for compositional structure.

None of this, of course, diminishes the work, and the museum's complementary display of 19th-century fossils from the Delabole quarry, which were sold by quarry-workers to visitors, adds a pleasing contextual footnote to the slate circle. And whether we try to square the circle or not, Long has a strong claim to being the most important artist of the age.

The exhibition continues until the end of April at Bristol City Museum and Gallery, 0117 9223571