THE CORCORAN has a shock in store for those who think of Britain's Tony Cragg as a lively, witty and inventive minor sculptor. Cragg, the Corcoran shows us, is a genius who's likely to be ranked among the great artists of this century.

Overuse of superlatives has sapped the snap and crackle of language, but only superlatives will do for this exhibition of works Cragg has created since 1975. The Corcoran, built to a grand scale in an ebullient era, has for the moment found works equal to its monumentality.

Scale is central to Cragg's work. He makes great big things, whose size may at first seem to be bravado but which soon reveal themselves to be just right. As a poet and prophet of the post-industrial era, Cragg has progressed from showing us the ironic beauty of our trash to revealing the limitless promise of material mastery.

Look what you've done to the world, Cragg used to carp. See what you could do with the world, he now croons, luring us into his vision with beautiful and beguiling shapes, textures, colors and materials. Bronze, plaster, glass, wood, lapis lazuli, steel, sandstone, plastic, granite, rubber, cast iron . . . . Whatever comes to Cragg's hand is transmuted into whatever he wills it to be.

Sugar beets, for instance. Nothing on this planet is more ordinary and ugly than a sugar beet. In "Inverted Sugar Crop" (1986), Cragg gives us cast-bronze sugar beets, with pumpkin faces carved in them. Well, not pumpkin faces exactly, more like the faces on the piled corpses in concentration camp photographs. Well, no, not Holocaust heads exactly, nor something in between. They're both one and the other, grin and grimace, promise and warning.

Similarly ambiguous is "Code Noah" (1988), whose title and gene-echoing helix suggest a theme of world-with-an-end, amen. But the bronze spiral is made up of cuddly teddy bears and toy elephants and other nursery animals. It probably is an apocalyptic preachment, but it's also as endearing as Winnie the Pooh.

"Minster" (1987), several cunning stacks of junked tires, gears, flywheels, flanges, bell housings and whatever becomes, at second thought, an elegaic evocation of the ruins of Camelot, or the Kremlin, or Disneyland. The message is timely and timeless.

Some of Cragg's largest works seem to be entirely playful feats of derring-do, such as giant monolithic eucalyptus boles, towering sandstone bottles, humongous steel-pipe assemblages that challenge us, compel us, to stand there and take it in. Some are so massive that they promise to outlast history; others seem so delicate you tiptoe past for fear they'll shatter or topple.

And every piece is consummately executed. Cragg's skill is equal to his imagination, whatever the material at hand. In an era when lesser sculptors use deliberate slapdash to conceal their clumsiness and ignorance of their craft, Cragg's superb castings, flawless carvings and deeply thoughtful assemblages seem revolutionary.

Cragg well may come to curse the day when he began constructing his signature pieces, the scenes and figures made up of plastic objects and fragments found on beaches and in the streets. They're wonderful assemblages, sprightly and amusing, and occasionally have real power, such as "Newton's Tones" (1978), which echoes and honors the great scientist's discovery of the spectrum of light. While inherently limited, they're so distinctive they've become a label under which "Cragg, Tony (1949- )" can be conveniently filed.

But not after you've seen the Corcoran show (which was organized by the Newport Harbor Art Museum of Newport Beach, Calif., and, amazingly, is Cragg's first solo American museum exhibition). There are a half-dozen of the found-plastic mosaics among the 29 works on view, and some of them are huge, but they fade to a decorative frieze under the impact of Cragg's mighty "made" works.