Who or what could lure a young Scottish laird to damnation on his wedding day? A Sylph who's airborne rather than earthbound, of course, but one who's irresistibly magical as well. Alessandra Ferri, who danced the title role in American Ballet Theatre's production of "La Sylphide" yesterday afternoon, with her physical beauty and allure, was the perfect sorceress -- untouchable, inhuman, but vulnerable enough to delude an impulsive young man into thinking he could possess her.

Ferri's sweetly amoral Sylph, with her demurely seductive eyes, exquisite arms and passionate temperament, gave the performance its high romantic color, and filled in the holes left by the sketchy acting of her James, Julio Bocca. And Bocca's extraordinary dancing -- leaps as high as flight, feet that flashed through beaten steps and shyly slid into near perfect finishes -- gave the ballet the bravura edge that Ferri's light and polished dancing lacked.

Had Ferri's feet fluttered as quickly and prettily as her hands, had Bocca's mime the exuberant clarity of his dancing, this would have been a transcendent performance. But both dancers are very young and fairly new to their roles, and they caught the spirit of August Bournonville's "ballet poem" well enough to bathe the Opera House in gas light for an hour or so. There was true tragedy here that one felt in the gut -- a love whose flame burned so dangerously high that it destroyed pure beauty, a boy too young to understand what he'd done, or what he'd lost -- even if one had to take the metaphysical underpinnings on faith.

Two more experienced dancers, Martine Van Hamel and Ross Stretton, gave a mature and mellow reading of the ballet at the evening performance. Stretton danced James as an ordinary fellow who sees his one chance of escaping reality and goes for it. Van Hamel, a light though stately Sylph, was also attracted to pretty things, whether young men or golden rings, without thinking of the consequences. Though both have danced more crisply, they caught the lightness and roundness of the Bournonville style perfectly. This was a pleasant and moving performance that never quite seared the soul.

Marie-France was a pretty, practical Effie, the jilted fiance'e, at both performances. At the matinee, Wes Chapman was a happy-go-lucky Gurn, the equally practical suitor who wins Effie in the end. In the evening, Michael Owen was a crafty but rather domesticated Madge, the witch on whom the plot hinges, and Deirdre Carberry nearly stole the second act with her beautifully bubbly dancing as the leading sylph.