As Barnum, the title role of the new Broadway hit, Jim Dale is giving the musical comedy performance of several lifetimes.

Singing, swinging, dancing, wirewalking and evoking the now dimmed buoyancy of 19th-century America, Dale's is one of those rare, electric creations that tingles the spine. One delights in the skills this dazzling performer flings out so audaciously.

Though such actual figures as Jenny Lind, Susan B. Anthony and Tom Thumb ar among its characters, don't look for literal history on the St. James stage on New York's 44th Street.

P.T. Barnum, whose photos suggest he was a pretty porky gent, didn't look a whit like Dale, who is lithe, lean and athletic. There isn't a shred of evidence that the Swedish Nightingale, as her contemporaries dubbed Lind, tapped the Barnum libido. And that asinine coin named Anthony is no less unreal than the cardboard figure assigned to the cast's presentable Jaren Trott. While Jumbo didn't arrive in America till two years after the show ends, the elephant, who almost caused a war between England and America, is amusingly depicted on stage.

Perhaps the approach to its historical figures is defined through that given Barnum's early star, "Tom Thumb." Born Charles Sherwood Stratton in 1838, he grew to only 2 feet 1 inch in his teens and finally reached 40 inches and 70 pounds when Queen Victoria dubbed him "general" in 1863. The normal-sized Leonard John Crofoot merrily plays, sings and dances; thanks to ingenious scenic perspectives by designer David Mitchell. "Bigger Isn't Better" sings Crofoot, scoring a subtle point for a relatively small cast of 22 that seems to number hundreds in the magic of Joe Laton's staging. c

Scorned in some quarters, Mark Brambles's book serves the feel of the whole with some ingenuity, more impressionistic than factual. Roaming the United States and Europe from 1865 to 1880, when Barnum linked up with Bailey, the book has the effect of broad, vivid pointillism, a dotty valentine to the period's gaudy elan.

This kind of book construction replaces the traditional and-then-and-then-and-then scheme through colorful dots, wholly imaginary meetings, much in the sytle E.L. Doctorow popularized with his "Ragtime" and which Garson Kanin employed in "Moviola," last week's TV mini-series. You can object to it, as many do, but the melange conveys the energetic optimism and innocence now perceived as 19th-century America.

Within Bramble's impressionistic outline, Layton has staged the whole in a marvelous frenzy of activity. There is not a single instant when someone or something is not moving on stage; a rope coming down, a platform sliding on, balloons breaking loose, plates flying, bricks being tossed, as in that long-standard act called "The Bricklayers." Through a fine job of casting, Marianne Tatum has both the voice and beauty to suggest Jenny Lind.

Early on, Barnum's eye settles on a supposedly ancient black woman named Joice Heth. His imagination quickely turns her into George Washington's 126-year-old nurse. In Hershy Kay's wholly contemporary orchestration, the roly-poly old lady sings "Thank God I'm Old." In the role, roly-poly, energy-bursting -- and youthful -- Terri White brings down the house, as she later threatens to do in several other personifications.

Vital to the whole is Cy Coleman's bursting, martial, whoop-de-do score. Barnum introduces himself with "There's a Sucker Born Ev'ry Minute" and winds up with another characterful number, "The Prince of Humbug." There are rousers such as "Out There," "Come Follow the Band," and "Join the Circus"; ballads for Barnum and his wife, and an aria for Jenny. Michael Stewart's lyrics tie each number to its spot.

With "Sweet Charity," "Seesaw" and "On the Twentieth Century" among his stage hits -- and "Hey, Look Me Over" and "If My Friends Could See Me Now" in his melody parade -- Coleman's "Barnum" score is his best yet, certain to be in the first big musical show record album in far too long. Look for it soon.

Vital to the effect of the Barnum portrait is the performance of Glenn Close as his wife. Close's assured acting glues the scattered scenes together as well as the period's adventurousness. The singing actress presents a key of humorous conviction leading us to care about her cocky husband, whose egoism was forgiven, in his time, by his total lack of jealousy.

Finally, however, all relies on Dale's Barnum, the greatest posthumous salute ever given the old showman. Dale beams up at the balcony with the aplomb of the old music hall artist this 40-year-old court never have been. He has a sharp, pointed nose not unlike Beatrice Lillie's, his acrobatics have true circus sauciness, his singing the sharp, nasal twang that would never do for Tistan but suits Barnum to the old P.T. It is the role of a lifetime and Dale clearly relishes every exhausting move of it.

British born and trained, Dale first appeared in America in 1974 with Young Vic's "The Taming of the Shew" and scored an immense hit the next year in "Scapino," neither of which played Washington. May Dale survive to bring "Barnum" to the National, as large a house as this compartively small show ever should play.

Layton's theatrical staging has inspired such other worthies as Theoni V. Aldredge in the costume department, the aforementioned Mitchell's scenic humor, and Craig Miller's spashy lighting.

There are, by the way, several area personalities involved with the production, which has won 10 Tony nominations. Co-producers are Irvin and Kenneth Feld, of the family that rose from Super Music City and the Carter Barron amphitheater to ownership of Ringling Bros.-Barnum & Bailey. Book author Bramble only a few years back was a Woodside High School student in Silver Spring. Leading lady Close made her professional bow in Shakespeare at the Washington Mountment a few weeks after granduating Phi Beta Kappa from William and Mary. Layton is in his 18th summer season staging North Carolina's "The Lost Colony." Next month Stewart and Bramble will be along at the Kennedy Center with still another new musical, "42nd Street."

Bright types all and, I should imagine, unanimously grateful that Jim Dale was born just in time for their glittery charade.