previewed here last night during the Corcoran Ball at the Corcoran Gallery of Art -- will strike thrill-seeking viewers as a little on the dull side. Henri struggled for the new, but didn't struggle hard enough. History rushed by him. His briskly painted portraits have somehow lost their daring. Late 19th-century artifacts, locked into their time, they're tamer than we thought.

Still, Robert Henri matters. He changed this country's painting. His kindness and his courage -- and especially his teaching -- were more important than his art.

Henri (1865-1929) taught Edward Hopper, Stuart Davis, George Bellows, Rockwell Kent, Patrick Henry Bruce, Paul Manship, Moses Soyer and a thousand other artists. (Many are represented in "Henri's Circle," a footnote exhibition now also at the Corcoran.) He didn't teach a technique or style, but something more elusive -- affection for the commonplace, distrust of the prissy, and willingness to wing it. His confidence was contagious. Henri helped prepare America for modernism. He brought an optimistic Whitmanesqe freedom to our art.

Henri championed dash. He abhorred the picky-picky. He was "a catalyst, an enthusiast, a healthy-minded man," wrote John Sloan, his friend and student. "He wanted the technique that could most quickly respond to life. Henri belonged to the quick-brushwork school . . . He had the nervous strength to be able to paint at high speed and concentration. . . . He used to say that the greatest portrait in the world could be painted in half an hour -- and he spent a great deal of his time and strength pursuing this ideal."

Those who wander through his show should look past the dull, dark suits worn by the men he painted, and past the just-a-bit-too-sweet faces of the children he so frequently portrayed. The chief lessons of his art are best seen in the swiftness, the assurance, of his brush. Look, for instance, at the way his thick strokes bring to life the bright white apron worn by the little Dutch girl he portrayed in 1907, or the way his brush evokes the rolling of the sea.

Henri loved the rough, and the roughness of the city. At a time when other artists were painstakingly depicting demure ladies playing lutes, Henri would happily lean out of his window in Philadelphia and briskly sketch the trolley cars. He would have agreed with Gauguin that "the ugly may be beautiful, the pretty never."

Henri preferred art for life's sake. He believed in the authenticity of the instantaneous response and in the unmediated gesture. "Work with great speed," he told his students. "Finish as quickly as you can. There is no virtue in delaying." The action painters of the New York School, and the Neo-Expressionist figure painters who have followed in their footsteps, and who scrawl their growling dogs with such unrestrained abandon, are all to some degree in Robert Henri's debt.

His name looks French, but isn't. He pronounced it "Hen-rye." It is, though his friends didn't know it, a made-up name, as American as a shoot-em-up.

Henri was born Robert Henry Cozad on June 24, 1865, in Cincinnati. Bennard Perlman's catalogue informs us that his father, John Jackson Cozad, "was a professional Mississippi riverboat gambler who invested his winnings in land development and real estate." He founded both Cozaddale, Ohio, and Cozad, Neb. In October 1882, he argued with a workman, pulled a pistol from his boot and shot the fellow dead.

The father, under indictment for first-degree murder (he was never caught) changed his name to Richard Henry Lee. The boy's name was changed to Henri, and he was referred to ever after as Mr. Lee's adopted son.

Henri enrolled in the Pennsylvania Academy of the Fine Arts in 1886, a school much marked by the teachings of Thomas Eakins, who had just resigned his post there. Soon Henri went to France.

The Bohemian life in those days was still relatively innocent and relatively sweet. Young Americans in Paris, wearing floppy artists' ties, spent their winters in the city and their summers at the beach sketching Norman peasants and speaking about art. Henri followed suit. He was much impressed by Manet and by the darkish colors of Goya and Velazquez. Rather daringly he turned his back on the highly polished finish of French academic art. When he returned to Philadelphia, he made his studio a good-natured version of a modern French salon.

Every Tuesday evening he invited in young Philadelphia painters. There might be a lecture by, say, a visiting Japanese artist who would demonstrate ink memory drawings, or a reading from Shakespeare (by an artist costumed as the Bard). Henri shared his Walnut Street studio with John Sloan. Later, when he moved to Chestnut Street, he took William Glackens as a studio mate, while Glackens, in turn, gave his studio to George Luks. The halftone had not yet been perfected, and most of Henri's young friends were earning their livings making drawings for the newspapers. Henri, fresh from Paris, made them all decide to give themselves to art.

"We became painters," wrote Sloan, "because Robert Henri had that magic ability as a teacher which inspires and provokes his followers into action. He was a catalyst; he was an emancipa- tor . . ."

By 1900, Henri, then 35, was already something of a star. He'd shown in three Paris salons and seven Pennsylvania Academy annuals. Though the rather snooty academic juries of the time found his art acceptable, they were tougher on his friends. At last, in 1907, when work by his associates was rejected by the American Academy of Design (of which Henri was a member), he organized a counterexhibition. The artists who showed -- Maurice Prendergast, Arthur B. Davies, Ernest Lawson and five Philadelphians (Henri, Glackens, Luks, Sloan and Everett Shinn) -- are known to history as "The Eight."

Most of them, following Henri's lead, produced images of city life. So disturbing were their pictures that Henri and his Philadelphia colleagues became known as "Ash Can" painters.

"It was the content, rather than the handling, that was shocking to the American public," Sloan would recall later. "The subject matter: It was not considered polite. People with taste wanted a kind of 'Ivory Tower' art . . . We were painting the everyday life of the American cities and countryside . . . We kept away from the social veneer of life.

"Instead of painting powder puffs," wrote Sloan, "we painted brooms."

Wherever he taught, in Philadelphia or later in New York, Henri always urged his students to be true to life -- and true to themselves. His school, wrote Stuart Davis, "was regarded as radical and revolutionary in its methods, and it was. The usual art school routine was repudiated. Individuality of expression was the keynote."

The trouble with Henri's show is that his expression no longer seems all that individual. His leprechaun-like Irishmen, blanket-wrapped Taos Indians and Spanish matadors, despite the boldness of the brushwork, look a bit too much like Central Casting types. Henri tends to flatter the children he so often paints, and his fashionable ladies too. His best portraits are those of his painting pals. In these handsome images, his good heart shines through.

The 100-picture show does contain surprises. Though Henri is best known for his portraits, his spontaneity produced some extraordinary landscapes. And his lack of prudishness allowed him to portray some red-haired nudes so lushly sexy that the painter's wife felt it necessary to publish a disclaimer in "Town & Country:" "Mrs. Robert Henri wishes . . . to announce that, although she herself has red hair, she does not pose for her husband's red-haired paintings."

Henri's taste was inclusive rather than restrictive. He sponsored art shows open to all comers and fought the art establishment on behalf of the rejected. Between 1907 and 1913, he was the leading liberator of American art. But all that was changed by the Armory Show of 1913. That astonishing exhibit pointed toward new realms -- toward Fauvism, toward Cubism, toward complete abstraction -- where Henri could not go. One still feels a pang of pity for poor Henri. Once New York's leading rebel, he was suddenly old hat.

The Henri exhibition was organized by the Delaware Art Museum. It closes June 16.