Popular "Mary Poppins" . . . Art of Walking By WILLIAM SOSKIN OVER in England, I hear tell, grownup ladies and gentlemen have been dressing in rompers recently, and have walked along London'! streets munching gingerbread, and have, been gazing starry-eyed and with a touch of whimsy at one another. This is due not to the fact that Mr. A. A. Milne has issued another bit of Winnie's Poohing. Mr. Milne is busy writing anti-war tracts and he apparently has no time for whimsy. No, the Britishers greet each other these days, if reports are not exaggerated, by referring to a Miss Mary Poppins instead of to Winnie the Pooh. "Pip, pip I" an Oxford man attired inpink rompers will say to a Cambridge-man in blue. "Mary Poppins 1" the Cambridge man will reply, and they will look at each other understanding. All this is due to the publication of a book, originally intended for children, but now adopted by all those, quaint grown-ups who liked to think of themselves as mere children at heart. It is called Mary Poppins, which is the name of the children's Nanny in the story; an acidulous Nanny, but one who can talk animal language and can take children to visit the stars or around the world faster than you can say Christopher Robin. She has a touch of the lepra-chaun in her, and a bit of behind-the-looking-glass atmosphere, and that leads its American publishers to suggest that Mary Poppins belongs in the company of Peter Pan and Alice in Wonderland. -