By Simon Johnson

STOCKHOLM, Aug 4 (Reuters) Magicians are flocking to the Swedish capital this week to test their skill at changing people into birds, producing playing cards from unlikely places and devising new ways of cutting a woman in half.

Around 2,500 magicians in town for the World Championships of Magic will see 150 top exponents of the art compete for the Grand Prix a two-week contract in Las Vegas or performances in Paris, Monte Carlo or London.

One illusionist even planned to cut a woman in half and get her two halves to crawl around the stage independently.

Magic is the art of ''making the impossible possible,'' said Swedish illusionist Julien Dauphin, whose own act involves his assistant and girlfriend, Angel, setting fire to a coffin with him in it.

This is the first time the World Championships, held every third year since 1948, have taken place in Sweden. China, Spain and Austria are competing to hold the next competition.

Some conjurors have been performing on the city streets, but the competition itself is billed as ''Magicians Only.'' Nor are members of the public allowed at the lectures on magic or the magic market, where illusionists can pick up the latest design in cages for escapology, a new magic wand or a bunch of plastic flowers to appear out of a fold-away top hat.

''It would be a bit like finding out that Father Christmas is your dad in a red costume and a beard,'' said one magician.

In recent years some magicians have shown the public how tricks are performed, sparking howls of protest from colleagues.

Eric Eswin, magician and president of FISM, the International Federation of Magic Societies which organises the championships, is less concerned.

''Sometimes we are too secretive about the secrets,'' he said.

''There are 14 ways of cutting a woman in half. Even if they explain one on television, you could do it again in three months and 90 percent of the audience would have forgotten.

Nor does knowing how the trick works necessarily spoil the enjoyment. ''It is the performance and the charisma of the magician,'' Eswin said. ''I am not looking for the secret, I am appreciating the performance.'' A peek at the market and you can understand the magicians' concern. For 800 dollar you can buy the damask-covered table floating in mid-air next to one stall complete with instructions.

Next door, spoons, forks and keys were showing an alarming tendency to bend in half in the hands of Israeli magician Erez Moshe, who was happy to reveal his secret for 30 euros.

Performing the trick, however, is another matter and three days later Moshe's sleight-of-hand remains just as impressive.

''Maybe I'll compete next year,'' Moshe said. ''Right now, I'm filming a TV special in Israel.'' REUTERS SSC BS0901