What innovative sculptors have been up to

It's altogether too easy, especially when confronted by the truly extraordinary things that have happened in painting over the past century or so, to forget that modernist sculpture has been at least as revolutionary and innovative. We need only compare the work of Rodin and Saint-Gaudens with that of Brancusi, Calder, and Hesse, to note the dramatic changes that have occurred in sculpture since the 1890s. And if we want further proof, it can be found in any exhibition devoted to the sculpture of recent years.

``Transformations in Sculpture: Four Decades of American and European Art,'' currently at the Guggenheim Museum here, goes one step further and presents detailed evidence of just how significantly three-dimensionality in art has continued to change over the past 40 years. Its roughly 120 works by 58 artists fill most of the museum and demonstrate how successive generations have expanded modern concepts of sculpture. The pieces on view represent a wide assortment of movements and methods, and were drawn from public and private collections in Europe and America, as well as from the Guggenheim's own permanent holdings.

Particular attention is paid to the work of three seminal sculptors active during the late 1940s and 1950s: the Swiss Alberto Giacometti and the Americans David Smith and Joseph Cornell. Giacometti comes very close to stealing the show, not only because of his startling originality, but also because everything he did transcended style and formal effectiveness to touch upon and illuminate specifically human concerns.

His ``Four Figurines on a Base,'' ``City Square,'' and ``The Chariot'' are not only thoroughly ``modern'' in a formal sense, but in a psychological and philosophical sense as well. No one else in our time has presented human vulnerability as simply and with as much dignity and integrity as he. As a result, no matter how much we may prefer to see ourselves as robust and invincible, we cannot help but acknowledge that his perception of human nature as fragile and tentative also has the ring of truth.

David Smith, on the other hand, was more concerned with purely formal matters, with a greater flexibility of process and technique, and with a broader acceptance of iron and steel as legitimate materials for sculpture. That he knew what he was doing is proven in this show by ``Voltri VII'' and ``Cubi XXVII.'' The former is a large, rather humorous piece made of iron that rests on two wheels and a flat form, and the latter, an equally large but more radiant construction fashioned out of stainless steel.

No one in recent years has been more adept than Joseph Cornell at creating intensely private and haunting interior worlds out of tiny odds and ends picked up on the street or in variety stores, snippets of magazine and newspaper stories, carvings of birds and other objects, and photographs and reproductions of old master paintings. These were carefully arranged within small boxes that occasionally resemble tiny cabinets and at other times dimly lit miniature stages. Several of the best of these ``privat e worlds'' enrich this exhibition, including ``Space Object Box: `Little Bear, etc.' '' and ``Untitled (Medici Princess).''

Other outstanding pieces are by Dubuffet, Di Suvero, Edward and Nancy Kienholz, Rauschenberg (his ``Monogram'' is one of the classics of the post-World War II era), Hesse, Kelly, Klein, and Singer. The only questionable works are by de Kooning, although I must admit that Andre's ``Lead Piece (144 Lead Plates 12 in. by 12 in. by 3/8 in.)'' appears sillier every time I see it.

Since ``Transformations'' was intended to be -- and is -- a highly selective survey of some of sculpture's most significant recent developments, it is neither all-inclusive nor strictly up to date. Even so, it presents a rather remarkable overview of what many of our more innovative sculptors have been up to these past 40 or so years.

At the Guggenheim Museum through Feb. 16. Masterpieces of the American West

Anyone who takes the time to see ``Masterpieces of the American West,'' at the American Museum of Natural History here, is in for a special treat. In galleries not far from the museum's stuffed lizards and turtles, the visitor will come upon an altogether fascinating exhibition celebrating the wonders of the American West as seen through the eyes of as varied a group of painters as ever set brush to canvas. There are pictures of Indian life painted by George Catlin in 1832; mountain and prai rie landscapes by Moran, Bierstadt, and Blakelock; depictions of cowboy life by Remington and Schreyvogel; studies of Indians at war and at play; and some canvases by more recent artists detailing what they saw and felt while visiting or working in the Far West.

The 91 paintings by 74 artists range from the precisely realistic to the totally abstract, and include examples by Durand, Russell, Dixon, O'Keeffe, Benton, Marin, Pollock, and Frankenthaler. Some may be a bit too pretty or romantic for contemporary urban tastes, but every one embodies an important aspect of Western life. They are on loan from the Anschutz Collection, which owns roughly 500 works of art documenting 150 years of American history, and which regularly sends exhibitions like this to museums

throughout the United States.

At the American Museum of Natural History through Feb. 16.