The melancholy barmaid--lost in a distraction fit--rises like a Venus from a haze of light and laughter. She is solid as a statue. Nothing else is firm.

The painted scene around her pulses, flickers, flies apart. She is haloed by a stuttering, an odd disjunctive rhyming of bottles, flowers, chandeliers. Two round white lights behind her stare out like blind eyes. Two small feet, at upper left, stand on a trapeze. She is caught between two worlds, the mirror world and ours. Her mirror does not work as normal mirrors do.

It skews the laws of space and bends the laws of time. Her reflection ought to be immediately behind her, but is shifted to the right. The ghostly man she serves appears to stand where we stand, though we know that cannot be. He is a presage or a memory. Her vacant gaze assures us that he is not there.

"A Bar at the Folies-Berge re" was painted by Edouard Manet more than a century ago. It is the masterwork that closes his triumphant exhibition on view through Nov. 27 at the Metropolitan Museum of Art. The painting seems to occupy--as does the woman it portrays--a moment that exists in and out of time.

Manet (1832-1883) was older than Ce'zanne, Monet and van Gogh, yet his sense of time seems newer. Nothing in art history prepares us for the way he chops a moment into pieces. He prophesies the future. He intercuts the past.

His great and complex paintings here--"The Luncheon in the Studio" (1868), "The Balcony" (1868-69), "The Railroad" (1872-73)--and those that could not make the trip--"De'jeuner sur l'Herbe," "Olympia," and the National Gallery's "Old Musician"--are strangely discontinuous. Eliot's verse and Joyce's prose are filled with shifts as sudden. Abrupt leaps--from sitcoms into newscasts, from ball games into game shows--shear televison's flow. We have learned to see the splinterings, the quantum jumps, embedded in what once seemed continuity. Manet saw them first.

The viewers of his day were used to reading paintings as one might read a story. They expected noble sentiments and clarity of plot. Manet disappointed them. The longer they examined his "realistic" pictures, the more they looked like dreams. His stories made no sense. His "contemporary" scenes quoted the Old Masters. Manet's paintings opened thought paths that turned out to be dead ends.

That apparently straightforward work, "A Bar at the Folies-Berge re," swirls with innuendo. It simultaneously suggests innocence and sexiness, noisiness and silence, mystery and candor, drollness (the small trapeze) and sadness (her dark eyes). She was not a professional model, but a woman named Suzon actually employed at the Folies-Berge re. But those who recognized her face--the place was all the rage--found little satisfaction, for Manet nagged them on with other recognitions. That still life on the counter--was it not a reference to the Dutch masters or Chardin?

The picture confounds expectations. While its triangles and grids, its bottles and its flowers dance in rhymed complexity, the cropping at its corners seems offhand, photographic. It clearly is a studio work, obviously posed. Yet its sunny flicker calls to mind the art of the Impressionists, whose ranks Manet refused to join. The painting's forms--now concrete, now ephemeral--could hardly be more varied. Suzon's rounded wrists have ivory's solidity. The right hand of her customer is but a blob of gray.

Her loneliness suggests that portrayed by Edward Hopper. The white circles in the background are as crisp as Thomas Downing's. We cannot know her thoughts. Yet ours are set free.

When Manet died of syphilis at 51 in 1883, Edgar Degas, who knew him well, said, "He was greater than we thought." Manet resists our knowledge still. No 19th-century painter is more difficult to classify.

He was reluctant and impulsive, conservative and radical, admired and dismissed, absolutely confident and deeply apprehensive. Championed by Zola, Baudelaire and Mallarme', he was a member in good standing of the Paris avant-garde. The friends with whom he chatted almost every evening at the Cafe' Guerbois included many of the most advanced artists of his day: Ce'zanne, Degas, Renoir, Fantin-Latour and Sisley, the photographer Nadar, Pissarro and Monet. Yet he longed to be accepted by the establishment authorities who ruled the French Salons. He was never a bohemian. Manet was a gentleman, a boulevardier, a dandy. His manner was most elegant, his tailoring impeccable. Even when affecting the drawling slang of Paris, "he never achieved vulgarity," wrote a boyhood friend. "He was obviously a thoroughbred . . . There were few men so attractive." Yet this gentleman of fashion tore into the canons of accepted taste.

Despite his sweetness and politeness, he flew sometimes into rages. When in 1870 the critic Edmond Duranty objected to the oyster shells in Manet's "Philosopher," the painter slapped his face. The two men fought a duel in which the critic was slightly wounded. Reconciliation followed. "Manet behaved very well indeed," Duranty said, "and I have the highest esteem for him."

To hear the college teachers tell it, there are at least three Manets. There is Manet the inventor, whose formal innovations--the boldness of his patterning, the "flatness" of his space and the way he pinned his figures to clouds of gray or brown--changed the history of art. Then there is Manet the historian, who filled his complex pictures with cunning quotes from Raphael, Titian, Velazquez and Watteau. And there is Manet the reporter, the streetwise observer who portrayed changing Paris, its fashions, its cafe's, its railroads and street fights. (This reportorial Manet was the subject of "Manet and Modern Paris," last winter's exhibition at the National Gallery of Art.) There are other Manets, too. There is Manet the psychologist, the ironist, the prankster. The more we know about him, the more elusive he becomes.

As if dodging history, he left few quotes or writings. He seems a sort of realist--he painted prostitutes and beggars, news events and cafe's--yet his "realism" jars. His pictures often offer disturbing incongruities--the oysters underfoot, the naked woman at the picnic in "Dejeuner," the black cat in "Olympia," those feet on the trapeze. One never doubts his seriousness, and yet he contradicts it. He teaches with surprises, he promotes the artifical. He dares to flirt with farce.

His drawing was not masterful. He resisted for good reason the seductions of high finish, for unlike Raphael or Ingres or the young Picasso, he did not have the draftsman's gift. He was one of those French masters--like Ce'zanne, Matisse, Duchamp--who thought his way to greatness. His courage was astonishing. One feels it in each picture. He was not afraid of accident. He was open to the risky. He cared deeply for the way the face can show the soul. He cared for old art, too, and for the life of modern Paris. And he held all this in balance. But it is not psychology, or history, or reportage that was his chief concern.

One subject rules his art. Manet painted painting. It is the moment of the moving brush, the instant in which memory bursts into discovery, that he cared for most of all.

Every brushstroke tells in every painting by Manet. To read his pictures clearly one must view them in the flesh. Photographs won't do. They drain his works of subtlety, they muddy up his colors. No camera can capture his blacks and nuanced grays.

Reproduction, it turns out, also does his modeling a distinct disservice. The famous flatness of his painting, adored by art explainers, has been exaggerated greatly. It is true he relies often on single-color passages--the red trousers of "The Fifer," the blue-black cloak of "The Philosopher" and the jacket of black velvet worn by his adopted son in "The Luncheon in the Studio." But except in reproduction, these passages aren't flat. They've been sculpted into roundness not by light-and-shade, but by the movements of his brush.

No painter of his day could manipulate moist oil paint more fluidly than Manet. Two vastly different photographs of his "Portrait of Emile Zola" are published side by side in the New York exhibition's huge and superb catalog. One was taken head-on, as is normal. The other one, however, was made in raking light. The first looks flat and structureless. But the second, writes Anne Coffin Hanson, "shows the changing textures of the thinly painted dark eye socket, the firmly delineated bridge of the nose, and the brushstrokes that respond to the swellings of the cheeks and brow . . . It is as though the artist had discovered a means of simultaneously combining touch and sight."

Dead 100 years, Manet once again disturbs conventional assumptions. He has done so from the start.

"The Luncheon in the Studio," perhaps the most impressive painting in the show, poses questions it won't answer. Why, the viewer wonders, is the figure in the straw hat cut off at the knees? What is his relationship to the woman with the coffeepot, to the bearded man in gray? When the painting was first shown in the Salon of 1869, the critics expressed bafflement. One complained about the oysters and the half-peeled lemon remaining on the table while coffee is being served. The'ophile Gautier was comparably disturbed by the cat, the swords and helmet gathered in the foreground. "But why these weapons on the table?" he asked in his review. "Is this the luncheon that follows or precedes the duel?"

The viewer, now as then understandably bewildered, attaches his attention to the certainties provided--the youth's fashionable dress, the black velvet of his jacket, the yellow of his hat, the rhyming pointed forms (of coffeepot and helmet, tablecloth and leaves), the half-Dutch still life at the right, the brushstrokes on the silver. Manet here, as always, forces us to sight.

The 190-object exhibition in New York includes unfamilar portraits--two of Georges Clemenceau and two of Berthe Morisot, one sweet, the other wild--that take the breath away. It was organized by Franc,oise Cachin of the Muse'e d'Orsay, Paris, and Charles Moffett of the M.H. de Young Museum of San Francisco, who once worked at the Met. Warner Communications helped to pay its bills. Admission is $4, with tickets sold on a first-come, first-served basis, and none sold in advance.