Two beautiful pieces of public sculpture went on view in Washington last month: Nancy Holt's "Waterwork," a long, airy structure made of gray-painted six-inch plumbing pipe and permanently placed on a soft green hill near the Kendall Demonstration Elementary School on the Gallaudet College campus, and James Rosati's "Triple Arc I," a glistening set of intersecting arcs made of welded and polished steel and temporarily installed in the paved courtyard of the American Institute of Architects headquarters building.

The pieces, sponsored by clients with differing aims in different parts of the city, have nothing to do with one another. Their appearance at the same time is totally coincidental. And yet, because the pieces are so strikingly dissimilar in intention and effect, this coincidence raises interesting questions concerning the state of the art of public sculpture.

Rosati's abstract piece, which inaugurates a welcome rotating sculpture program established by the American Institute of Architects, is a splendid example of the type of work that has come to dominate the landscape of public art in the last three decades. It is possible to very much admire the daring expertise of its manufacture and respond to the crystalline elegance and improbable precision of its geometry, and still come away feeling that there is something missing -- that the piece, though it nicely accentuates the sheltering curves of its architectural setting, somehow fails to say anything important about why it is there. Conceived in isolation, with no notion of the space in which it might be displayed, "Triple Arc I" refers almost entirely to itself.

Holt's piece, although by no means lacking in spatial surprises, is by contrast richer in communicative possibilities. This is because it was made to order for the specific setting, and because it engages certain simple but inescapable environmental facts -- namely the infrastructure of water pipes that normally is hidden underground. "Waterwork," the most recent and best of the pieces commissioned as part of Gallaudet's program of public sculpture, is just as serious an art piece as "Triple Arc I," but it also is openly playful, and this metaphorical and visual wit gives it yet another pleasing dimension.

Art historian Albert Elsen, writing in a catalogue for a recent exhibition of Rosati's monumental sculptures, notes that Rosati "has not accepted commissions that ask him to interpret the client's business or what an institution stands for, nor that require creation for an existing site. Corporations and cities have learned to accept the artist's vision." This approach clearly places great value upon individual artistic creativity and conscience -- a necessary precondition (though no guarantee) of great art. But it can and too often does produce what is unkindly but aptly disparaged as "plunk art," meaning art works placed in parks or plazas without much thought to visual and symbolic relationships. This can happen to the best of artists -- an earlier Rosati piece, commissioned by the General Services Administration, is so poorly sited and so out of scale with the plaza of the Hubert Humphrey Building that it is hardly distinguishable from nearby benches or traffic bollards. Even more importantly, this attitude places definite and unnecessary limits upon the possible roles public sculpture can play.

Yes, works of art in public places should be the very best the artist can imagine and make, but such works also can and should strive mightily to establish meaningful relations with a particular spot. These include not only the physical dimensions and other visual aspects of a place, but also its social characteristics -- its history, its present-day uses, its future potentials. The argument about public sculpture often is cast in terms of a split between abstract and representational art, but this is misleading. Adherence to one style or the other is no true test of a work's quality, unless the viewer comes to the piece wearing ideological blinders that rule out one or the other.

Traditional representation does, it should be said, offer the possibility of immediate access to historical (or religious) events in ways that abstract works do not, and figurative pieces are often more immediately accessible in their meanings to a broader portion of the population. But one need not go outside of Washington to find figurative works that fail miserably -- the bathetic Boy Scout Memorial near the Ellipse probably is the best (or worst) example -- or abstract works that triumphantly succeed, such as the Washington Monument or the wall of the Vietnam Veterans Memorial. In other words, figurative works can be "plunk art," too.

If pure abstraction has been the prevalent mode of public sculpture in recent decades, discontent with its performance has produced a number of positive reactions. These range from anecdotal trompe l'oeil figuration, as seen in Lloyd Lillie's bronze chess players in John Marshall Park; to traditional fountains such as the one David Phillips ornamented with lily pads and frogs, in the same park; to full-blown classic revival allegories of the kind that Washington sculptor Raymond Kaskey created with his 27-foot-high figure of "Portlandia" for Michael Graves' municipal office building in Portland, Ore.

But reactions to the predominance of pure, formalist abstraction have by no means been confined to artists working in traditional figurative modes. Vanguard artists, too, have participated in this process of creative rethinking and, again, one does not have to go farther than Washington to find pertinent examples. Rockne Krebs created here an exhilarating new form of civic sculpture with his inimitably site-specific laser structures. Yuri Schwebler, emphasizing forms and environments related in various ways to basic physical forces or to the history of public art forms (the magnetic North Pole, for instance, or the Russian Constructivists), was an early urban earth artist. Jim Sanborn, whose "Lightning and Other Earthly Forces" was selected for the Hirshhorn's current "Content" exhibition, continues to explore this evocative vein. Ed McGowin created the first of his hybrid "Inscapes" while living here, and though the piece (in the 1200 block of 19th Street NW) is in sad repair today, the idea of using strong abstract forms as containers for provocative narrative tableaux remains as potent as the day it was conceived. (It is interesting to consider the Vietnam Veterans Memorial in this context. It, too, is a hybrid, a joining of abstraction -- the wall -- and representation -- the statue of three soldiers -- that is successful despite having been forced.)

Nancy Holt, a New Yorker who recently received a commission to supervise the reclamation of a huge garbage dump in the New Jersey Meadowlands, has added significantly to this broadening lexicon of public sculpture in the Washington area, first with her "Dark Star Park," a merging of art and landscape architecture completed this year in Rosslyn, and now with her inventive "Waterwork."

Located on a grassy hill in the rear of the Kendall School (near the West Virginia Avenue entrance to the Gallaudet campus), "Waterwork" at first glance seems to be more industry than art, put there perhaps by an engineer with a sense of whimsy and a distinct feeling for clean lines. But the Rube Goldbergian good humor of the piece, as it zips up from the earth and down into it again, serves several purposes well: The "hands-on" playfulness (the pipes are comfortable to sit on in spots, and the water can easily be turned on) reflects the psychology of its location next to an elementary school, the use of everyday (though usually invisible) materials undercuts the idea of art as something set apart from the environment, and the general wit of the configuration makes the ultimate seriousness of the piece all that much more surprising and delightful. One discovers this serious intent by degrees. At first one is simply enchanted by the play of lines in space, as exciting, in its way, as that of any piece by Mark di Suvero. Then one becomes aware of the sense of ceremony in the progression of lines: The pipes divide and soar upward, like gates, and when one enters there is a good view, right on line, of the Capitol dome. Eventually one gets the point: The piece is a fountain that reverses conventional expectations. That is, its normal mode is off, but the viewer can simply turn a valve and the water runs into a sequence of basins.

"From these basins," the artist writes, "the water flows into the city sewer system and eventually out to sea, where with evaporation and rain, it returns once more to the rivers, streams and reservoirs to be recycled through the city water system." That straightforward, poetic idea -- making art and making a place out of the mundane innards of the urban environment -- is the fresh kind of symbiotic connection among art, artist and place that contemporary public sculpture needs if it is to attract and hold our attention as a lasting source of wonderment and pride.