Here by the filthy train trestles of North Station stands basketball's sweet Garden of sweat.

This is the home of the Boston Celtics: grean-clad keepers of the flame.

Once again, they are turning sooty, smoke-filled Boston Garden into America's least-likely gallery of fine art. Masterpieces-in-motion are once more a display.

In this Louvre of the underwear game, the third coming of the Celtics may be on its way.

Just as the arrival of Bill Russell in '56 and Dave Cowens in '70 transformed the Celts into world champs, so the appearance now of Larry Bird has jolted this team and its town like an electric shock to the heart.

It isn't the acrid blend of cigar and pot smoke hanging in the rafters around those 13 world championship flags that has Boston fans rubbing their eyes. Frankly, this city can't believe what it is seeing.

Last season the Celtics were a disgrace to their heritage -- dead and stinking to heaven.

Worse than merely bad (29-53 in '79), they were repulsive to those who savored Celtic tradition. What could be more ironic and bitter than a Celtic team rich in talent but adjectly poor in spirit?

For 20 years, from '56 to '76, it always seemed appropriate, if accidental, that in all of American pro sports only one team was nicknamed after a non-Indian race of men: Celtics.

Indeed, Boston basketballers thought of themselves as a separate breed within their own game -- men set apart not by talent so much as by an idea of how their game should be played.

"I was disgusted by what we had become," says Red Auerbach, president and general manager, thinking back on 103 losses in the last two seasons. "I was ready to get out."

Now, Auerbach may eventually become the first man in pro sports to be the central figure behind the construction of three dynasties with the same franchise.

The Celtics not only have the best record in the NBA (19-5), but their staggering margin of superiority -- 11 points per game -- is more than twice that of any other club.

"We're blowing away good teams now -- just destroying them. What will we do later?" says veteran Don Chaney, who played with Russell and has seen all three eras.

"We're nowhere near peaking. We barely know each other. I'm afraid to say what might happen by March."

Even Boston brass has to scratch its head and hold its breath at the transformation it has wrought.

"I don't have time to relish it. I'm too buy worrying," says Auberback. "I don't know if we're for real. I know that we're not deep and that injuries could kill us."

But them, injuries can kill anyone. Don't by coy, cigar face.

"I have to force myself to see the game as it really is -- especially our mistakes -- rather than let myself fall in love with the final score," says new Celtic Coach Bill Fitch, a rare black-board-and-film workaholic who is also a wit.

"I keep thinking that if we go into a lull, we'll come to a stop like a turtle with air brakes. In my job, you don't get to enjoy. You only get to suffer."

Fortunately, Boston fans show no such reserve. The one consensus about these new Celts is that they have -- no one knows how -- already excited their fans more than any previous team.

After having one sellout in three years, Boston had eight in its first 11 home games (all Celtic wins). Attendance here, traditionally scandalously low, is suddenly second in the NBA.

"Celtics: Greatness in Green," says one of the handmade signs created by Rita, the super-fan, who had stopped her colorful cottage industry in disgust the last two years.

"M. L. Carr runs on Green Gas," and "Ford: A Winning Idea," are her paeans to newly arrived sixth-man Carr and unheralded guard Chris Ford.

The apparently mysterious transformation of the Celts from the second-worst team in the NBA to the early season leader is far simpler than it appears.

Boston had been twice blessed: they have gained by addition and they have gained by subtraction.

In the last seven months, the Celtics have gotten a new owner (Harry Mangurian), a new coach (Fitch), a new central star (Bird) and a new catalytic sixth man (Carr).

Just as important, Boston lost a meddlesome owner (John Y. Brown) and a half-dozen players not cast in the Celtic mold.

All this was made possible when Brown took his fried chicken, his wife Phyllis George and his political ambitions to Kentucky. "I feel sorry for Kentucky," said one Celtic after Brown was elected governor. "Can a state finish last?"

The sources of the Celtics' misery new seems obvious. Two owners -- first Irv Levin, then Brown, pushed a succession of dumb trades of Auerbach.

Presenting the fundamentalist Auerbach with Sidney Wicks, Bob McAdoo, Billy Knight, Curtis Rowe and Marvin Barnes was like tying a teetotaler in a chair, then forcing gin, scotch, rum, brandy and vodka down his throat.

"The higher-ups were making the deals," says Boston guard Tiny Archibald, "and the person who was supposed to make deals (Auerbach) didn't have the authority to veto them."

"It got almost unbearable many times," said Auerbach, "Sonny Werblin held the (New York) Knick (GM) job for me for two years.

"Then, when Levin left and Brown came in, I decided to give it another shot. But that got so bad that I was ready to leave again."

Auerbach and Mangurian have hit it off perfectly. "Not a single disagreement," says Auerbach.

"That's because Red has gotten his way on everything," grins Mangurian.

And that, it now seems, was all the Celtics needed.

The new atmosphere -- almost one of athletic resurrection -- is evident in everything the Celtics do.

"The losers are gone from this locker room. Now, the old feeling is back," says Chaney.

As the Celtics romped through a practice session in the empty Garden one morning last week, they sounded like an enthusiastic high school team, teasing each other with all the playground jive that constitutes a private language.

"Sweet J . . . Give that man a ticket . . . Who laid that brick? . . . Get outta here, little man . . . That was me-an'-you, and mostly me," goes the banter.

The first man at practice every day -- often by hours -- is Bird.

His acceptance has been total -- primarily because his style of play is pure Celtic, a sort of taller, slower, more risky version of John Havlicek.

"I call him 'Kodak,'" says Fitch, "because his mind takes an instant picture of the whole court. He sees creative possibilities, especially passes, that have never been done."

To the Celts, Bird is like a 6-foot-9 Christmas toy that blocks shots, works diligently on defense, and, above all, tries to make his teammates look better. "And," smiles one Celtic, "he's nice an' mean. He'll bank anybody."

When Bird makes one of his marvelously deft passes in practice, the other Celts let out a high-pitched twitter: "Birdie-birdie-birdie."

Perhaps the new Celtics are closest, however, when they are engaged in a Fitch ritual -- communal film study.

Lounging in their locker room after practice, they make a sort of color-commentary on a videotape replay of the previous night's game -- the kind fans will never hear.

Archilbald appoints himself the supreme arbiter, pointing out a constant stream of mistakes, nearly invisible lost opportunities, and universal selfishness.

"That's right, Cornbread," needles Archilbald. "Don't pass it to Red (Cowens). He ain't workin' hard enough."

The Celtics snicker.

"That's right, Max" crows Archibald as Maxwell shoots while Cowens waits for the pass in vain. "Make him a rebounder."

Occasionally, the Celtics fall silent, listening to Bob Cousy doing the play-by-play on the TV replay.

"I'd like to say something critical about Bird," says the Cooz, "but basically, he's just superb in every area of the game."

The Celtics go dead quiet, biting their lips with suppressed amusement as they wait to see how the painfully shy Bird will react to the sort of broad praise they would never grant to each other.

Bird, dressed just like what he calls himself -- "a hick from French Lick (Ind.)" -- tugs at the tractor-driver's cap on his head, pulling it even lower over his beaklike nose.

"Them guys," mumbles the expressionless Bird, looking down at his shoes, "sure know their basketball."

The Celtics howl. Bird's drollery, so dry and understated that it even causes double takes among the hip pros, has struck again.

As the Celtics start to leave the locker room to go home, the irrepressible Carr accidentally lets a dollar bill drop from his pocket -- just to see who will bend for it.

Instead of universal cool (the worst sign for team morale), several Celtics dive for the cash. Carr spins and grabs it himself.

"I always leave a trail behind me," says Carr, delighted with his exit-line for the day.

If Bird is Boston's conspicuous infusion of talent -- $650,000-per-year worth, then the infectiously cheerful Carr is the epitome of what the Celtics have always been about.

"Carr exceeds the sum of his technical parts as much as any player in the league," says Celtic beat man Bob Ryan of the Boston Globe.

"And it would be worth $100,000 a year just to have him sit in your locker room."

"Carr has always been a Celtic at heart," says Auerbach. "After he got out of Guilford (College), we gave him a tryout. I released him. But I helped him get a chance to play ball in Israel."

Carr never forgot the favor. He made his way through Europe to the ABA to Detroit, never losing his humor. On signing with the Pistons, Carr announced to a stunned press conference, "I'm changing my name. From now on, I wish to be known as Addul Automobile."

Actually, Carr -- the most sought-after free agent in the NBA after last season -- signed with Boston for less than other clubs offered him.

"We got him," says Auerbach, "because he believes in the chemistry of good people working together, just like we do."

A season ago, Carr not only led the NBA in steals and scored 18.7 points-per-game, but was third in the league in minutes played -- a pro's most precious possession.

So, on being made sixth man -- with his minutes slashed to 26 a game and his scoring average whittled to 14.3 Carr said, "I'll be happy as sixth man, seventh man or eighth man."

Said, the folk of Boston would agree, like a true Celtic -- old or new.