Behind the scenes, lease-renewal problems again threaten the future of downtown Seventh Street as a viable commercial gallery center. But on the face of it, the core galleries at 406 Seventh St. NW seem to be thriving, and are currently filled with strong shows -- sculpture in particular -- ranging from new work by well-known New York postminimalist Jackie Ferrara to unknown work by talented newcomer Lisa Scheer. There's even a dollop of 19th-century French academic sculpture (including Carpeaux) at Osuna, which is also featuring paintings from the estate of Washington Color painter Howard Mehring, who died a decade ago.

Meanwhile, across the street, alongside Zygos Gallery, there are other encouraging vital signs, as recently arrived Zenith Gallery prepares to expand into additional space next week, and a newly opened cafe sprouts lines of eager customers at lunchtime. Could seer Robert Lennon's dream of a lively arts corridor between the Mall and the National Portrait Gallery/National Museum of American Art be on the verge of happening? Or will "406" -- like Gallery Row just opposite -- become more office space for the FBI? Stay tuned.

Jackie Ferrara at Kornblatt

Jackie Ferrara has become one of the most admired of American sculptors, both here and abroad, since Max Protetch first introduced her in his Washington gallery in 1975. In her current show at B R Kornblatt Gallery -- a high point of the season -- seven important works attest not only to Ferrara's staying power, but also to her growing power to mesmerize.

Ferrara fashions her reductive, modular sculptures from squarish strips of pine, poplar or redwood (Lincoln-log construction, but without notches), creating architectural forms that conjure ancient civilizations, temples and altars, but are, in fact, pure invention. The commanding, seven-foot-tall "Semaphore," for example -- a stepped pyramid made of pine lightly stained gray-green -- is stacked so that small openings repeat, or increase and diminish in size, creating rhythmic beats, or patterns, on the surface that hint at underlying mathematical sequences. Decoding them -- or rather attempting to -- engages the mind, as the eye is seduced by the pure sensuousness of the surfaces and the beauty of the craftsmanship.

Some of Ferrara's drawings -- elevations, cross-sections and views from the top of these sculptures looking down -- give a sense of how these patternings were designed to interact in three dimensions, as inlaid forms on one side echo openings on another. They graphically illustrate how clearly the artist thinks in three dimensions, and -- to some extent -- why it is so rare that one feels "finished" looking at one of her better works. "Square X" is another fine and mysterious piece that, in its patternings, also incorporates a distinctively postmodern look.

Ferrara arrives at Kornblatt Gallery just in time to resonate with a new show of work by Joel Shapiro at the Hirshhorn. Shapiro, like Ferrara, derived his pared-down formal language from minimalism, but has also transformed it into something very personal. How nice it would be if Ferrara were invited to create a site-specific piece to soften the Hirshhorn plaza.

The Kornblatt show, which opens today, will continue through Jan 6. Hours are 10:30 a.m. to 5:30 p.m. Tuesdays through Saturdays.

Lisa Scheer at McIntosh/Drysdale

Washington metal sculptor Lisa Scheer is having an unusually impressive first solo show at McIntosh/Drysdale, after surfacing in "Options '87" at WPA. At WPA, Scheer created a large, environmental piece that was so full of pent-up energy, it sent at least one viewer fleeing for fear of being overcome.

In her new wall reliefs at McIntosh/Drysdale, this obviously prodigious young artist continues to work in rusted sheet steel, cutting it into rectilinear, shard-like pieces that she then solders together into dynamic clusters, combining three-dimensional spirals, obelisks, ziggurats and chambered nautilus forms. In some ways, they have the look of scored, folded paper, and are, in fact, worked out in cardboard.

The sculptures often cantilever dramatically into the surrounding space. And though no energy has been lost in these new works, it has been most effectively harnessed and put to work in these seemingly self-generating arrangements of cubist/futurist-derived abstract forms that somehow manage to hint at narratives dealing with, appropriately, the unleashing of forces by ancient gods.

"Inanna's Descent," for example, based on an ancient Assyrian myth, seems to shoot energy from the sky, as does "Khat," in which a lightning bolt-like form is loosed. In the end, though titles range from "Leviathan" to "Mookie," the real subject here is energy seeking expressive form. And it does.

Scheer's show will continue through December, and gallery hours are 10 a.m. to 5 p.m. Tuesdays through Saturdays.