THEY MAY BE often overlooked by foreign visitors dashing from one world capital to another, but the provincial museums of France house some of Europe's greatest and least-kmown treasures. They are museums filled with art that has accumulated over the countries -- often by sheer chance.

Assembled chiefly through private gifts (until a decade ago, without tax benefits) these collections are understandably less comprehensive than those plundered from all over the world by the royals, and now ensconced in big-city museums such as the Louvre. Nonetheless, each provincial museum has its own speical strength, wonder and surprise.

The Musee des Beaux Arts in Rouen, on the Normandy coast, is such a museum -- one of the best in France -- and because Americans so rarely go to see its treasures, the museum has now come here. "French Master Drawings From the Rouen Museum" begins a four-city American tour at the National Gallery of Art West Building Today.

The show brings the best from Rouen's collection of more than 9,000 drawings, and surveys French draftsmanship during one of the richest but least-known periods in the nation's art: the late-16th through the mid-19th centuries, a period often best remembered -- and usually written off -- for its fluffy Madame Pompidou portraits, and courtiers in powdered wigs and phony shepherdess outfits. There was, it turns out, a great deal more to French art during those centuries, and scholars as well as casual viewers will find their percepitons both revised and enlarged by what they see here.

The Rouen Museum's drawings collection began back in 1822 with the aforementioned a gift of 100 drawings collected by Rouen-born artist-collector Lemonnier. It only became a world-class collection, however, in 1975, when its holdings were tripled by collectors Henri and Suzanne Baderou, who gave about 3,500 drawings, including the splendid red chalk drawing on creamy white paper called "Head of a Boy Wearing a Plumed Hat," by Jacques Bellange. The 1979 transfer of the Hedou collection from the municipal library (to which it had been bequeathed in 1905) provided 3,500 more drawings, including a powerful head of an old man with downcast eyes attributed to Fragonard.

Persistent strains of these centuries, from the classical to the romantic, are illustrated in an often superb examples by Bellange, Simon Vouet, Charles Le Brun (the great chief decorator of Versailles), Hubert Robert, Jacques-Louis David, Theodore Gericault and Eugene Delacroix. One of three pastel drawings by the short-lived, early 18th century master Antoine Watteau -- "Sheet of Studies: Six Heads, and Hands Holding a Flute" -- is in itself worth the trip. TAmong the surprises are little-known works by famous artists: a bold little "Lorraine Landscape" by Jacques Callot, providing a breath of fresh air in a sea of early 17th-century academic nudes; and an astonishingly vigorous, spontaneous charcoal sketch of two sailboats by Jean-Francois Millet, who is far better known for his contrived and sometimes maudlin scenes of sowers and reapers.

There are also startlingly beautiful works by artists long forgotten: Pierre Puget, a leading 17th-century French sculptor, is represented by "Sailing Ship Before a Promontory," an exquisite ink drawing on parchment; Lemonnier, who donated the first 100 drawings, could obviously draw as well as collect; Michel-Francois Dandre-Bardon, who -- like many 18th-century French Artists -- spent several years at the French Academy in Rome, is represented by a fine study of feet and hands that shows a sense of living flesh that was rare at the time; Claude-Louis Chatelet's mad delicious watercolor landscapes, including "View of the Island of Capri."

An attempt has also been made, in this selection, to give some sense of the works that have a special connection with Rouen, and here some fascinating items emerge. Poussin, considered the greatest French painter of the mid-17th century, was born in Normandy, and the museum is very proud of its recently acquired drawing by that artist, despite its relatively poor state. Jean Jouvenet of Rouen, a follower of Poussin, is less famous but considerably better represented in several works that show passion despite their academic underpinnings.

The Rouen Museum is rich in the work of native son Theodore Gericault, who died in 1824 at age 33, and what a loss that was becomes painfully clear in four splendid drawings on view. Despite his short life, the artist made a major reputation as the painter of the famous "Raft of the Medusa, " now in the Louvre. The genesis of that painting, based on an actual comtemporary shipwreck, can be seen in more than a dozen studies in the Rouen Museum.

One study for "Medusa" is included in this show, along with a drawing that deals with another sensational current event: the murder, in Rome, of the public prosecutor. How French art had changed since the days of the cool, distant, idealizing academicism of the 17th century!

Eugene Delacroix, another great 19th-century romantic painter, often traveled to Normandy, and once explained in a letter to a friend how his watercolor "St. Barnabas Healing the Sick" -- also shown here -- came to be: "I was obliged to spend a day and a half in Rouen while awaiting a conveyance to bring me here [to Valamont]. There at the museum, I painted a watercolor after a magnificent Veronese that you would enjoy seeing. If you ever have the slightest business in Rouen, combine it with a viewing of this painting, which alone is well worth the trip."

So is this show. Organized by the International Exhibitions Foundation, "French Master Drawings From the Rouen Museum" will continue at the National Gallery through Sept. 13, and will then travel to the National Academy of Design, New York; The Minneapolis Institute of Arts; and the J. Paul Getty Museum in Malibu, Calif. A hefty catalogue accompanies the exhibition.