Taking the long view: Roni Horn's allusive serial art makes use of pairings, sequences and minutes compositional shifts. An eight-month, two-part exhibition at New York's Dia Center recently enabled viewers to experience the subtle mnemonic qualities of her work

"Identity is purely mathematical--it has no place in real experience, in actuality," says Roni Horn. (1) What she means is that no two encounters with a person, object or place are the same. But her choice of words, always exact, is telling. Most of us think of identity as the single irreducible thing that defines character, or place, or culture. To Horn, identity thus understood is deeply suspect, for experience cannot be repeated, nor, as a consequence, verified.

Presenting her work at New York's Dia Center for the Arts gave Horn an exceptionally good opportunity to put this conviction to the test. Dia's unusual scheduling system, in which artists typically are invited to occupy an entire floor of the building for nearly a year, often results in installations that change midway, generally to present related, but distinct, bodies of work. Ideally, viewers see both installations, and carry the memory of the first when viewing the second. This kind of half-remembered, half-observed perceptual experience is a central structuring element in nearly all of Horn's work. At Dia (as with her other recent installations), individual features of objects and images matter less than what happens between and among them--and those relationships are seldom simple. "Thwarting the narrative," Horn has said with respect to an earlier series of photographs, "is an important way to engage people's interest." (2)

First to be encountered at Dia, and one of two works present throughout Horn's entire eight-month project, was a photo installation called This is Me, This is You (1999-2000). On each of two opposing walls was a grid of 48 color shots (each 12 1/2 by 10 1/2 inches) of a girl mugging for the camera. Her remarkably large blue eyes are consistently arresting, but all else--facial expression and body language, clothes, hair and demeanor--changes dramatically from frame to frame. The photos show the girl at a time of particular flux (she ranged between the ages of 8 and l0 during the lengthy period over which thy photos were shot), and while sometimes beautiful, her self-dramatizing grins and grimaces as often make her seem painfully awkward, perhaps enough to deflect close, critical viewing. That may be one explanation for an almost unavoidable first impression that the two grids of photographs are identical. In fact, they are composed of related but significantly different images (corresponding positions within the grids present neighboring frames in the same roll of film): what seems a tidily symmetrical set of reflecting images is actually a thoroughly warped mirror.

One issue in this work is propriety, both formal and social. The girl in the photos, who is Horn's niece, reveals herself without inhibition; while altogether chaste (in contrast to the abundant sexy-young-girl photography lately shown in New York), the imagery has the emotional intimacy suggested by the informality of the title. This is Me, This is You relies, both verbally and visually, on the semantic promiscuity of pronouns, grammatical shifters which Horn tosses around as if they were dice. The questions the title deliberately begs--who is speaking and who is spoken of?--are repeated by the perceptual wobble in which viewers are caught. Sent shuttling from one set of pictures to the other, the audience searches in vain for a fixed subject.

If the changeability of a young girl's face appeals to Horn, she has also explored fluidity in another, more elemental form in several extended series of photographs of natural and artificial bodies of water. Especially in a freely flowing river, water proverbially lacks self-identity (that is, you can never step into the same stream twice). Its almost infinitely variable character is explored in Some Thames (2000), an 80-image sequence of photographs of which 32 were included in the first installment of Horn's Dia show. (3) All represent the same short stretch of the river and are tightly framed, excluding anything not aqueous (there is neither shoreline nor horizon, and no boats, bridges or people). But visual information abounds. Horn finds a stunning variety of texture in the Thames, which sometimes assumes the aspect of polished stone--granite, obsidian--and under other conditions looks like beaten brass or zinc. It is shown pitted and pocked by rain, churned by currents, oiled by indeterminate spillage and flecked with foam and debris. All the things you can do to paint with a brush, or to stone with a carving tool, seem exemplified in these images: the water is swirled and troweled, etched, chiseled and gouged. Color ranges just as broadly, from steely blue-gray to pure cobalt to pale milky blue, from grayish green to amber, from lavender to black.

Horn would like to install the full set of 80 photographs (which have never been shown together) in a continuous sequence throughout a single building, with the water images flowing uninterruptedly between public and private spaces. It would be a model, Horn says, of a kind of "lateral monumentality," a term that relates to public-art practices by others of her generation: Tom Otterness and his peers in the early-'80s collective Colab used similar words to describe the penetration of public space by inexpensive, widely distributed objects and images. The strategy was taken a step further by the late Felix Gonzalez-Torres, with the stacks of offset photos or printed texts he designed to give away for free. Horn, who was a good friend of Gonzalez-Torres, says he would never have embraced her phrase, and, indeed, in her usage it has a meaning distinctly different from his and Otterness's. Rather than describing a pattern of public distribution, it suggests a bid for space and attention that is as incrementally, insidiously aggressive as the action of water on rock.