The National Gallery of Art has bought "The Fall of Phaeton," a turbulent, fantastical masterwork by Sir Peter Paul Rubens, the most fluid and inventive of Northern Europe's baroque painters. The canvas, which depicts an ecological catastrophe -- the chariot of the sun careening through the sky, the hours in disarray, and the earth below in flames -- will go on public view Wednesday, the 350th anniversary of the Flemish master's death.

The picture comes from the collection of a private London owner. Market sources speculate that an early Rubens of such quality must have cost the gallery at least $3 million. The purchase price was not disclosed.

The "Phaeton," unlike many later works that bear his name, is entirely by Rubens. He painted it in Italy, probably in 1605, many years before that busiest of painters established his factory-like studio with its small army of collaborators, students and assistants. Looking at this picture, one somehow gets the feeling that the artist when he painted it was sort of showing off. Rubens, who in 1600 had gone from Antwerp to Italy at age 22, already had absorbed high Venetian color, Michelangelo's muscularities and the ripe myths of the ancients by the time this work was done.

Phaeton (he's the naked youth tumbling from the heavens) was the importuning son of Helios (or Apollo) who, as adolescents will, begged his father for a chance to drive the family car -- which, in this case, was the horse-drawn golden chariot of the sun.

As Ovid tells the story, the god at last relented, the hours yoked the horses, dawn threw wide the stable door, and Phaeton started driving the sun across the sky -- with disastrous results. He couldn't keep the steeds in check, he dropped the reins in panic, and the sun, out of control now, at one point dipped so low that it set the world on fire.

Enraged by such chaos, Jupiter (or Zeus), the father of the gods, hurled a thunderbolt at the charioteer "and thus quenched fire with blasting fire." The maddened horses leaped apart, the golden car was totaled, and Phaeton, the unfortunate, fell headlong to his death.

In Rubens's vision of the myth, the thunderbolt is implied by a blast of golden light that cuts across the scene from upper right to lower left. The mighty horses twist in space; the dismayed and winged hours are tossed about like autumn leaves.

Although the gallery already owns half a dozen canvases assigned with confidence to Rubens, among them the imposing "Daniel in the Lion's Den" of 1613-15, this is the first of Rubens's mythological extravagances to enter the collection. The others, for the most part, seem stiff as living statues when seen beside "The Fall of Phaeton." Rubens loved the subject. He painted it again in 1636. Throughout his life he kept returning to mythological car crashes (for instance "The Death of Hippolytus," from the Fitzwilliam Museum, Cambridge, which was displayed here last year) perhaps because such imagined visions let him demonstrate the gravity-defying tumblings, rhythmic baroque swirlings and magical foreshortenings at which he had no peer.

The subtext of the Phaeton myth -- he who messes with authority, with God-given order, does so at his peril -- appealed to Rubens too. For though the innovative freedom of his brush strokes, and the swirling of his spaces, have influenced such artists as Van Dyck and Fragonard, Delacroix and Watteau, Boucher and Frank Stella, Rubens was a radical only in his painting. Throughout his long career, he was unswervingly obedient to the Catholic Church in Rome, and to princes who held power.

His Latin was most elegant. He spoke and wrote with fluency in half a dozen languages -- German, Italian, English, Spanish, French and Dutch. The French have an expression -- "stupid as a painter" -- but in no way is that insult applicable to Rubens. More than just an artist, he was an architect, a humanist, a businessman, a skillful antiquarian and a diplomat as well. "Of all his talents," said his friend, Gen. Ambrogio Spinola, "painting is the least."

Rubens -- "the painter of princes, and the prince of painters" -- was known throughout Europe as a diplomat. In 1630 he negotiated a peace between Spain and England, receiving for his efforts a diamond ring, a jeweled sword and a knighthood from King Charles I of England. In 1631, he was knighted once again, by Philip IV of Spain. Rubens, who at age 13 had signed on as a page to the dowager Countess of Lalaing, was as comfortable in court as he was in his studio. His art and his diplomacy gave him constant entree to the palaces of Europe. In Brussels, where he was appointed court painter to the archdukes of the Netherlands, Rubens was excused from all taxes and guild restrictions. Princes great and small, Protestant and Catholic -- the Medici of Florence, the Gonzaga dukes of Mantua, the princes of the church, and the kings and queens of France -- held that widely traveled painter in the highest of regard.

American collectors, however, especially the sort who forged the National Gallery's permanent collection, long have found Rubens's fleshy nudes, his scenes of violent action and his Counter-Reformation images of martyrdom, well, just a bit excessive. Dutch 17th-century painting, with its democratic spirit and meticulous precisions, is still better represented in American museums than is the often-pagan, spirited and myth-accepting art of Catholic Flanders.

The "Phaeton" acquisition suggests that that imbalance is at last being righted. It also may be read as a sort of anticipatory grace note to the Van Dyck retrospective -- Van Dyck was one of Rubens's most devoted students -- that the National Gallery will open in the fall.

The "Phaeton" is first recorded in an Antwerp inventory of 1657. It was sold by Christie's, London, in 1775, and thereafter catalogued in the collection of the Earls of Caledon before being sold, once again by Christie's -- though this time misattributed to Abraham van Diepenbeeck, a follower of Rubens -- in 1939. The painting has been recognized as a rediscovered Rubens since the 1950s.

"The Fall of Phaeton" was acquired with monies from the gallery's Patrons' Permanent Fund. It is three feet high and four feet wide. The canvas, despite its age, is in excellent condition, though Arthur Wheelock, the gallery's chief specialist in Northern European painting, says it was coated with thick, discolored varnish when it arrived last year. Since then it's been cleaned by the gallery's David Bull. Surrounded by a 17th-century Italian gilt frame, it is on view in Gallery 45 of the West Building.