Nizette Brennan's ambitious show of stone sculpture at the new Wallace Wentworth Gallery, 2006 R St. NW, finds her in the throes of shifting from the small-scale, sensuous and intimate approach for which she is best known hereabouts, to a large-scale public one. Because it covers the past seven years, the show offers a telling look at how this determined and imaginative artist has felt compelled to move on -- if not always ahead -- in search of new forms.

The earliest works remain, for this viewer, the most fulfilled: made from rounded river stones, they are minimally cut and combined into a series of primal, altar-like pieces made for the artist's sculpture garden in Pietrasanta, Italy, the world's great stone-carving mecca where she studied in the late '70s. After a stint as an assistant to Isamu Noguchi, Brennan began thinking in terms of larger, environmental works, and the model for one of the best of them -- "Marketplace Pi and Talents" (1980) -- is here: a limestone piece made of eight pie-shaped segments that lie flat on the ground, several scooped out, and then refilled with their own chipped, crumbled or rounded bits of stone.

A child of foreign service parents, Brennan is referring here -- as in several related pieces -- to the "talent" as an ancient unit of money, and it is a form and configuration that has become her hallmark. The full-scale version of "Marketplace Pi" was purchased by the Rouse Co. and now floats in a pool at the White Marsh Mall.

Since then, the possibility of other site-specific commissions -- notably in Bethesda -- has inspired other projects, the best a witty sundial called "Solar Farm," which, with luck, someone still might build. A more serious piece, titled "Cut Boulder/Split Stone," echoing the dramatic angle of the National Gallery East Building, combines various elements of the sculptor's basic technical vocabulary, and cuts, splits and juxtaposes natural and manmade masses of stone to dramatic effect.

It is during the past two years that a distinctly new vocabulary of forms has been developing while the intensity of the work has been diminished. Leaving more challenging issues of primal evocation and sculptural process behind, such pieces as "The Great Wicomoco" are, in fact, no more than semi-abstract imitations of cresting waves with worked surfaces that are irrelevant and merely decorative. Setting them in sheets of corrugated aluminum webbing to imitate the sea is simply too literal a device, and does not solve the artist's ongoing concern with incorporating the base into the work. So far, this series, titled "Wetlands," remains unresolved, with the possible exception of "Chincoteague, " which stands determinedly -- and amusingly -- atop a classic column.

The show is a most welcome one, both for its depth and for the opportunity to see Brennan's ample -- and widely recognized -- talents unfold. The new Wallace Wentworth Gallery, at 2006 R St. NW, is welcome as well, adding yet another good gallery to a block that now includes Marsha Mateyka (where a Leonard Cave sculpture show also opens today) and Manfred Baumgartner, where paintings by Jacob Kainen are currently on view. Brennan's show continues through Dec. 8. Gallery hours are 1 to 6, Wednesdays through Saturdays.