A great artist never loses the ability to leave his audience breathless.

Consider Jacques d'Amboise. The man who decades ago became this country's first male ballet star, who as a leading dancer with the New York City Ballet for nearly 40 years awed audiences around the world. He is streaming up a steep sandstone slope on the northern edge of the Blue Ridge Mountains. And you're panting to keep up. Every now and then you catch sight of him slipping through the trees, his hair as gray as the rock.

D'Amboise is halfway through his quest to hike the Appalachian Trail, the rugged footpath that traverses 14 states. Nearly four months of tromping through mud and stone, fighting off black flies and nursing blisters has only quickened his pace. He's got those famously long legs, after all--never mind that he's had numerous surgeries on both knees and they crackle like popcorn when he bends them.

Never mind his arthritic ankles and his surgically webbed toes, sewn together to give them stability after repeated dance injuries. Never mind that some years ago, on another wilderness adventure, he lost most of an index finger to an infected spider bite.

D'Amboise--as he'll be the first to admit--is bullheaded. Bossy. Also relentlessly, unnaturally upbeat. And determined. He's hiking the trail's 2,160 miles to fulfill a long-held ambition--he's been an avid hiker since retiring from dancing 15 years ago. But mostly he's doing it to raise money for the National Dance Institute (NDI), the program he founded in 1976 to teach schoolchildren to dance. Along the way he's making a few dozen stops at schools, community organizations, even a prison, to teach the masses a perky little jig he choreographed, dubbed the "Trail Dance." He celebrated his 65th birthday this summer by teaching the dance to graduate students at Harvard.

The man who calls himself "the Johnny Appleseed of dance" is aiming to draw attention to NDI, to the physical fun and mental rigor required for dance and, by extension, the other arts. He hopes that donations to NDI will follow, so he can train teachers around the country in his methods for getting underprivileged kids, blind kids and those with other handicaps to move freely and fearlessly. (So far, approximately $250,000 has come in, mostly from people logging on to d'Amboise's Web site: www.ndi4all.org.) He plans to reach the trail's end at Springer Mountain in Georgia just before Christmas.

He's slept in rodent-infested shelters. He slogged through 20 miles of muck during the rains of Hurricane Floyd. Mile by mile, d'Amboise has been steadily approaching the Washington area. This week he's dancing at the Kennedy Center with children from Anacostia's Draper Elementary School, where d'Amboise has had a residency program for the past decade. Today he'll be at Annapolis's Maryland Hall for the Creative Arts getting midshipmen and others to jig, before heading back on the trail.

Park rangers at the base of Mount Katahdin in Maine jigged with d'Amboise as he began his hike in May, accompanied by his 42-year-old son, George, the oldest of d'Amboise's four children. Most Appalachian Trail hikers start in late winter at the southern tip of the trail. The weather is milder and the terrain friendlier. But d'Amboise--typically--decided to do it the hard way. He and his son figured if they got the harshest part over with--Maine's desolate Hundred Mile Wilderness, followed by the dreaded wind-scoured White Mountains of New Hampshire--they'd stand a better chance of sticking it out. (Each year, under 15 percent of the 3,000 or so who start the AT, as it's affectionately known, complete it.)

So there they were in the early-morning chill, d'Amboise, his son and the rangers swinging one another around by the elbows like it was a big happy hoedown, singing out: "Hel-lo, stranger, stepping along together. Hel-lo, stranger, stepping along with a friend. . . ." (D'Amboise also came up with the words and the music.)

D'Amboise's distinctively raspy, Jimmy Durante voice was hoarser than usual; he'd come down with bronchitis. Before he reached Katahdin's summit, a storm hit, spewing rain and thunder on the hikers. He was warned to turn back and wait a day. He didn't. It took d'Amboise seven hours to reach the top, at which point he drew himself up--his lanky frame was now the highest point in Maine, in the midst of an electrical storm--howled into the fog, danced a solitary jig on the rock and crept slowly, achingly down the other side. (The downhills are murder on his knees.)

Every dancer knows pain. In his years of performing, d'Amboise had his share of sprains, tears, twisted tendons and jammed joints. "I've been sore all my life from dancing," he shrugs. "It's my natural state."

You might even say some dancers are addicted to pain. Mikhail Baryshnikov endures three hours of physical therapy before each performance, and dances in knee braces. Ballerina Suzanne Farrell kept dancing after hip replacement surgery.

So what's a couple of burning lungs, a tormenting rash from poison ivy, bleeding bug bites and a banged up elbow or two?

Dancing in the Streets

D'Amboise credits ballet with saving him from the criminal-minded gangs of his youth. So would his mother, who sent him to dance classes along with his older sisters to keep him off the streets of Manhattan. This was in the 1940s, and not too many boys were taking ballet. But d'Amboise, who'd fallen in love with the physicality and structure of the art form, was undeterred.

"I never acted as if it was anything but great and exciting," he says. "You remember Tom Sawyer painting the fence? Imagine if he'd said, 'Oh, this is terrible. It's so boring.' But no--he said, 'This is great! Too bad you can't do this! Oh, all right, you can paint, but only if you give me your apple.' You see? I used the Tom Sawyer approach. I'd show the other kids the steps and challenge them to do them."

Who'd have thought that tough, wiry little Joe Ahearn would become the standard-bearer of the elite art of classical dance? But who better to encompass the postwar merging of European refinement and Yankee cool? The son of a French Canadian mother and Irish American father, d'Amboise was born Joseph Jacques Ahearn. The whole family took on Georgette d'Amboise's lofty-sounding maiden name after Jacques and his sisters became members of the New York City Ballet. But it was d'Amboise's all-American athleticism, his quick, powerful limbs and extroverted personality that won him international acclaim.

D'Amboise caught the attention of the great choreographer George Balanchine, who invited him at the age of 15 to join the New York City Ballet. Balanchine created some two dozen roles for d'Amboise, in such masterpieces as "Stars and Stripes," "Movements for Piano and Orchestra" and "Tchaikovsky Pas de Deux." D'Amboise also had roles in the films "Seven Brides for Seven Brothers" and "Carousel."

Through it all, he never forgot what the world of dance had brought to a New York street kid. And he longed to pass it on.

This urge became a steppingstone to a new career as the one in the footlights was waning. While still performing, d'Amboise started NDI to work primarily with boys, at first. He'd hold forth in several schools at once, choosing dozens of the most eager kids, drilling them once a week in preparation for a big production at the end of the year. But these weren't tights-and-slippers, place-your-left-hand-on-the-barre kind of classes. Not with d'Amboise bounding around the room, barking out steps in that foghorn voice, sweeping the kids into jazz- and street-influenced productions like the gangster tale "Fat City" and, last spring, "Step-by-Step-by-Ellington."

After retiring from the stage, many other Balanchine dancers have gone on to found and run companies of their own--among them Maria Tallchief, Edward Villella and Peter Martins, who took over NYCB after Balanchine's death. Still others are in demand as coaches of Balanchine's intricate choreography. But d'Amboise left the ballet world entirely.

"I decided that even though I could run any company I wanted to--and do it well--I didn't want to," d'Amboise says. "It was something that wouldn't challenge me. But going into a school and having 50 minutes with assorted children who may or may not want to dance! You don't have a dancing studio. You have a hall or a rooftop or a lunchroom or a corner of a gymnasium. And you have to get 50 children excited about dance. And one boy goes and puts his face in the corner and won't move. Right? Now whaddaya do? This is challenging. And much more interesting."

D'Amboise estimates NDI has taught more than half a million children in the past 23 years, about 2,000 a year in the New York area and thousands more in NDI residencies around the country, like the one at Anacostia's Draper Elementary.

D'Amboise's program "still leaves me flabbergasted," says Joseph A. Carter, Draper's former principal. "He set very high standards for the kids, and they saw they could be a part of something very beautiful. Behavioral problems were reversed--they disappeared. Attendance improved. It was remarkable."

"Here's a man who could be anywhere he wanted to be at any time he wanted," Carter continues, "and he chose to be with us. That made us feel really special."

Draper students performed for d'Amboise on national television when their teacher received a Kennedy Center Honor in 1995. D'Amboise's work with NDI has won him acclaim to rival his dancing years; among his other awards are the National Medal of Arts and a MacArthur Fellowship. In 1984, the year d'Amboise officially retired from dancing, a documentary on his work with children, "He Makes Me Feel Like Dancin'," won an Oscar.

Tired, but Tireless

D'Amboise's seven-mile speed hike up Cove Mountain was merely his afternoon activity. The day started with a 7:30 assembly at the Milton Hershey School for disadvantaged kids in nearby Hershey, Pa. D'Amboise, wearing a rumpled lipstick-red jersey, khakis and sneakers without socks, is carefully negotiating the steps up to the stage in the school's auditorium. As hundreds of grade-school children eye him dubiously--he's just been introduced as a famous ballet star, and he couldn't look less like a celebrity--d'Amboise shuffles stiffly up the steps, leaning nearly horizontal to heave his legs up over the lip of the stage.

"That introduction about being one of the great dancers--that's for a fellow of a long time ago," he announces breathlessly. "You'll see as I struggle up these stairs, I can barely get up. I used to be able to run and jump over a car. But dancing on cement floors all those years--you get beat up."

Moments later, these words are forgotten as he breaks down the Trail Dance for a group of kids who have joined him onstage, clapping out the rhythms, stomping heavily like he's squashing cockroaches.

"To dah right, to dah left, behind, in front!" he shouts, knees pumping.

The tape-recorded beat of the jig is contagious, but one boy, the littlest one up there, is getting flustered. Girls in the front row are snickering. "Shsh!" d'Amboise chides them in a stage whisper. "He'll get self-conscious. We're gonna make him better." D'Amboise swoops the boy up in his arms, polkas around with him on his hip, then sets him down to swirl on his own.

A couple of hours later, George d'Amboise and his father, now in shorts and a torn T-shirt, have piled into the NDI van amid a clutter of nylon rucksacks, wilted maps, mud-crusted water bottles and sour laundry. Lately, the two have been "slackpacking," meaning day hikes of 10 to 20 miles, toting only water and a boiled egg or two. Someone meets them at the end of the day with a car to take them to a bath and bed. As the trail heads into more remote country--through Virginia, Tennessee and especially the lofty Nantahala Mountains of North Carolina--they'll again don fully provisioned packs and bunk in the trail shelters.

"I'm eager to get on the trail," d'Amboise says impatiently, as the van idles in traffic. "If I'm not active I become a couch potato, my mind stops, I become a blob." He jiggles his knees and fusses over George, who won't be hiking this stretch to let an infected blister heal.

At the trail head at last, d'Amboise brushes past the FBI warning about fugitive Eric Rudolph. He wastes no time warming up. Jamming his hiking poles into the rocky earth with each step, he quickly disappears into the trees. A faint, breathy muttering accompanies the crunch, crunch of his feet. D'Amboise keeps a steady pace by humming ballet scores to himself.

"I've got a wonderful repertoire--'Petrouschka,' 'Stars and Stripes,' " he calls out over his shoulder. He sings out a march. "Bum bum, ba dee da BUM-BUM-BUM. Rum pum, ba dee da bum ba bum. . . . You feel the downbeat? It's one, one, one, one." He pumps his right hand like a conductor wielding a baton.

"Now if you change that to six-eight, it becomes light." D'Amboise skips past the pokeweed, skimming the ground as he whistles the jig from the Trail Dance. It's as if the tune carries him along.

"You see?" he says. "It has a lilt to it."

CAPTION: D'Amboise, on the Appalachian Trail to raise funds for his youth dance program.

CAPTION: The "slackpacking" d'Amboise, lightening his load for a while.