AT FIRST glance, the Manhattan apartment of Herbert Waide Hemphill Jr. looks like a "junque" shop. Whirligigs, whatnots and whatzits cover the walls and nearly every square inch of floor. There are lots of square inches of floor, because Hemphill is an heir to the Coca-Cola fortune.

The stuff is Americana, or folk art, or whatever you want to call it: objects made the way they are made because the person who made them felt like making them that way. Hemphill simply calls it art, and few will dispute him after seeing the cream of his collection, which goes on display Saturday at the National Museum of American Art.

The exhibit has all the life and color and dazzle of a circus, and the same kaleidoscopic effect. As soon as you turn your attention to Mohawk Indian Mary Adams's 1986 basketry wedding cake, your eye is captured by Howard Finster's "Model of Super Power Plaint {sic} (Folk Art Made From Old T.V. Parts)" (1979). From there the eye flits to lapsed preacher Edgar Tolson's ribald 1979 wood carving of Adam knowing Eve in the pre-missionary position.

According to the old rules of American collecting, such contemporary works could not properly be categorized as folk art, which was said to have ceased about 1850. By that time, the authorities used to assert, industrialization and improved communications had broken down the isolation of backwoods producers of arts and crafts. Outside influences and mass-produced materials corrupted the pure and innocent ignorance of our artisans, it was said, so that indigenous arts became cross-cultural and/or derivative.

Such rules no longer exist; Hemphill, 61, has blown them all away with his single-criterion collecting method: If it's American, and he likes it, he buys it, no matter when, where, by whom or of what it was made. It's just the sort of willfulness you might expect from a wealthy college dropout who never bothered to learn the rules of the art game before he started breaking them. He has come to dominate the field, and his rivals, trying to catch up, are running after him as fast as they can while kicking themselves.

Not the least of the joys of going through the show is the knowledge that it's all ours now. Hemphill has donated the whole shooting match to the museum, which now more than ever lives up to its name. It's hard to resent the idle rich when they so generously justify themselves.

Diverse as these 199 works are, they could not be more coherent. What their makers have in common is that they don't know or don't care about the way things spozed to be. They do naturally what all artists have always studied and striven to accomplish: to give tangible form to an idea.

Some of the pieces are so eccentric -- which is to say so uncompromising -- that it's not surprising to learn that they were executed by inmates of insane asylums. Others are so heartening, so American, that you want to grab a flag and wave it.

Hemphill has harvested the fruits of American ingenuity, and has distilled from them the essence of the American genius. His garden of earthy delights is a cornucopia of art of the people, for the people and by the people. It shows the silliness of such art categories as "folk" and "primitive" and "naive." Folk art? Like Hemphill says, it's just art, folks.

MADE WITH PASSION: The Hemphill Folk Art Collection -- Through Jan. 21 at the National Museum of American Art, Eighth and G streets NW. Open 10 to 5:30 daily. Metro: Gallery Place.