Turning the Hat Trick : HATS; Status, Style and Glamour <i> By Colin McDowell (Rizzoli: $50; 222 pp.) </i>

Hope, wrote Emily Dickinson, is the thing with feathers.

Hats, too--the things with feathers, jewels, model ships--you name it.

No less a tyrant of taste than Christian Dior declared, “I consider that without hats, an intrinsic part of fashion, we would have no civilization.”

Of course, the same can be said of decent burials, child-labor laws and animal-cruelty regulations, but this volume is not abashed about taking the Dior line: Hats are bellwethers of civilization, from the imperial state crown to the peasant’s cloth cap.

If whole books can be written about the history of corn or the pencil, then why not this handsome work, whose text, not overmatched by the pictures, speaks with startling assurance of the “semiotics” of millinery?

Consider: A fur hat, the first known in Europe, was found on that 5,000-year-old man recently hacked out of Alpine ice. Rhett tempted Scarlett out of mourning with a Paris hat. And 1950s sitcom writers couldn’t have managed without millinery, plots wherein Lucy buys an expensive chapeau, then spends the rest of the show figuring out how to keep Ricky from finding out. And all those hats that can still be as instantly recognized as the Coca-Cola bottle: Napoleon’s bicorne, the Phrygian cap of the French revolution, Daniel Boone’s coonskin cap, Sherlock Holmes’ deerstalker.

Author Colin McDowell, who has written about the couture of the British royal women, declares hats “the most unnatural of all items of clothing; they are the least necessary but the most powerful,” imparting as they do erotic, sporting, military or religious distinction, and conveying rank, chic, attitude, whimsy, regality.

Not to mention warmth and shade.

Frivolous as one may consider the topic, the book is close to social archaeology. The hat has served not merely as head covering but also an inflexible signaler of class and rank and politics through the ages, once as thoroughly integrated into culture and commerce as the microchip is now.

Take, for example, “hat honor,” the rigid rules governing doffers and doffees----who removed a hat and for whom. Men took them off for women, the lower classes for the upper classes, and everyone took them off for God.

Even the least engaged page-flipper, inclined to give hats as much current social relevance as Egyptian mummification rituals, must be caught by some great “Jeopardy!” moments:

Rose Bertin, Marie Antoinette’s milliner, originated the concept of “must have” and in time wielded the kind of influence that a defense lobbyist has today.

“Mad as a hatter” was no trifling phrase. Mercuric nitrate fumes inhaled by fur felt workers affected the brain and made many of them insane.

In an early PC gesture to animal rights, England’s Queen Alexandra, at the height of the fashion for plumed hats, was so upset at the slaughter of literally millions of rare birds that she refused to receive any woman whose hat was adorned with what we would now call endangered feathers.

McDowell does essay an explanation of the decline of the hat. But convertibles, youth culture, short hair, working women--none fully answers why hats became the dinosaurs of fashion. The dinosaurs, masters of the earth, vanished in a geologic flash--whoomf!--just as centuries of hat-wearing vanished in the 1960s. Even the names are like a forgotten language: trilby, billycock, shako, capeline, breton.

“Hats,” however, is no obituary. The surviving and reviving millinery industry is not cast as the Willie Loman of fashion. Millinery shops once lay as thick along American streets as frozen-yogurt shops do now. Surely, McDowell hints hopefully, the fashion industry--and a culture that has adorned every visible part of the body for years, and a few of the invisible ones, tattoo-wise--is not going to allow men and women go unprofitably bareheaded forever.