FROM 1789 until 1793, when she died in the embrace of Madame Guillotine, Marie Antoinette poured out her pleas for help, and finally her goodbyes, in letters penned on a delicate writing table.

Today this small treasure stands in the newly installed galleries of 18th-century decorative arts in the National Gallery of Art's remodeled ground floor.

The new galleries are important not only because these magnificent objects once again can be seen properly, but because they mark a new attention, if only a small one, by the National Gallery to decorative arts, acknowledged before only by polite nods in passing.

The desk, along with 17 other pieces of French furniture, the 176 brilliant polychromes of the Chinese porcelain collection, the nine medieval tapestries, the few pieces of late-Renaissance jewelry, the carved-rock crystal, the great Chalice of the Abbot Suger of St. Denis and four or five other works of church art, have been in hiding since 1972 when the Widener galleries were usurped for offices.

Not much is known about the objects, though research now is under way for a complete catalogue. For some years, the Widener gift of decorative arts was almost an embarrassment to the Gallery.

"We were patterned after the National Gallery in London, specializing in painting," explained J. Carter Brown, gallery director.

Brown admits that the only reason the trustees accepted the Widener decorative arts was because Joseph Widener wouldn't give his Rembrandt, Vermeer, Raphael, Titian and Bellini paintings unless the whole bequest was accepted.

"It's too late in the day to try to be all things to all people," Brown said.

The Marie Antoinette table is the only piece in the 18th-century French furniture galleries about which much is known.

Scholarship on French decorative arts is difficult because so many of the pieces were smuggled out of the country during the Revolution, leaving their provenance behind them.

The table is ornamented with capering cupids on ormolu plaques. Its small drawer is only large enough for the finest quill pen, its pull-out writing surface too fragile for any but the most gentle touch.

Not until the 1950s when Pierre Verlet, an authority on French royal furniture, happened to be in the gallery and looked at the palace inventory number underneath the piece, was the history of the table learned.

Another gem, a small writing and dressing table, is by the German-born Jean-Franc,ois Oeben (1720-1763), Louis XV's first cabinetmaker, and the teacher of Leleu, Carlin and Riesener, his successors.

The figurative marquetry on the table is a form of painting with wood, showing several delicately inlaid musical instruments and flowers. They seem too beautiful to be written on.

A clue to the table's ownership is found on top sections that fold back to reveal the much more assertively designed marquetry pictures of two fish, tied with ribbons. It is thought that the table was made for Oeben's patron, Madame de Pompadour, and that the comic fish were a private joke because she was nee' Poisson.

In line with the National Gallery's emphasis, Brown notes, the furniture is presented not as period pieces but individually, as works of art, as were the objects in the charming American furniture exhibit a few years back. William Williams, acting curator of decorative arts, worked with architect Dean Knott to design the new rooms.

Only the center room has elaborate French 18th century paneling, overdoor paintings and a handsome marble fireplace with a pictorial fireback of Orpheus and Eurydice.

Though the 18th-century paneling came to the gallery in a natural wood finish, it has been painted white, accented by gold leaf, in response to current scholarship.

The nine tapestries, dating from 1440 to the early 1500s, are presented in a great stone-walled hall with a magnificent fireplace at one end. Sculpture curator Douglas Lewis just has discovered it carries the coat of arms of the Barbo family of Venice. The 11-by-13 foot "Triumph of Christ," worked at 22 warps to the inch and commissioned by Cardinal Mazarin Tapestry, is remarkable for the intricacy of its goldwork.

Two of the smaller galleries have the feel of jewel boxes. The small alcove of church art centers around the amazing Chalice of the Abbot Suger of State Denis, circa 1140. Marie Antoinette was the last queen of France at her coronation to drink from the chalice with its colored jewels and pearls. The other small jewel case holds bijoux made for the Renaissance courts.

The Chinese porcelains include the huge Ch'ing chrysanthemum jars topped with Buddhist lions, circa 1700, and green Ch'ing jars in the Kuan shape. Fierce lions and a duck on a lotus leaf are great bursts of color in what are called "foreign ware," ornamented in the European manner. The oxblood vases ("bleeding drops of blood," as Williams put it), the crackleware, the celadons and the blues in the Chinese taste are especially strong.

Decorative arts have a very great appeal, perhaps because they are objects of everyday life, no matter how grand. They are meant to be touched, used, picked up, fondled. As Brown once put it, "They pass the most important test--they make you want to take them home."