Wedged between fat, marbled buildings and flashy, awning-fronted shops on Baltimore's North Charles Street is No. 217. All that's visible from the street is a tiny sign that says "Yogi Magic Mart" and a miniature window display. Inside, an elevator whisks you upward; when the door opens, you find yourself smack-dab in the world of magic.

Phil Thomas has spent more than half a century in this world of magic -- as magician, shop proprietor and magic historian. There aren't many in the magic world who haven't heard of Phil Thomas' Yogi Magic Mart. It's one of the world's largest magic shops -- mailing orders to every state and a dozen countries -- and home to the 400 members of Thomas' Yogi Magic Club.

Jumbled up among the shop's shelves are the more serious pieces that draw the collectors and magic historians: Antique posters of Thurston, draped in elegant cape; framed and signed pictures of a young and striking Houdini; hundreds of letters and props and clothing passed through generations of prestidigitators. The effect is a happy retail shop that doubles as museum.

"I love magic. It's as simple as that," Thomas says of his 50-year romance with the bizarre.

"Magic is a happiness business. You do it because you love to perform and because it simply delights people. Simple tricks. Difficult tricks. It's not in their complexity -- it's in the delivery. All of us love to make people happy." (His wife and partner, Anne, says he's the happiest man she knows.)

At one time or another, the likes of the great Blackstone, Jack Gwynn, Mark Wilson. Hen Fetch and hundreds of others have darted into his narrow little shop and performed on the tiny stage Thomas built for just such occasions.

On the first Saturday of each month, club members gather to learn, teach and perfect their craft -- or maybe just catch up on what's new. On the last Saturday of each month, beginners can join "Yogi's Youngsters" at 2 o'clock to learn simple tricks. If you get up and perform a trick yourself, admission's free; otherwise, it's 50 cents.

Amateur and professional magicians are constantly prowling the glass shelves and cases that line the shop's walls, in search of funny-looking colored powder, silvered top hats with giant holes in the back, stacks of glass globes, innocent-looking billiard balls and decks of cards. There are "how-to" books and thousands of combinations of "effects," the paraphernalia of the illusion art.

Thomas himself is a store of magic lore, knowing, for instance, certain elements of the world-famous Thurston picture-book act, in which the magician stepped, full-life, from the final page as it turned. And he knows the Blackstone secret of how the burro emerged from a bundle of silk.

His face lights up when reminded about the time, as recorded in magic history books, that Blackstone "was seized by masked, white-robed terrorists, tied in a sack and hauled up 12 feet in the air. A Ku Klux Klansman galloped from the wings on horseback and fired a pistol. The sack fell empty to the stage. The rider dismounted and pulled off his hood.He was Blackstone."

But if you aske the secret of such tricks, Thomas smiles and gives you a devilish look. He's not telling. What you think you see is more important than what you actually see. And therein lies most of the fun and almost all of the skill. As a gentle reminder of that edict, Thomas has a big sign posted in a prominent spot behind one glass counter: THE STORY IS TOLD WHEN THE TRICK IS SOLD.

"Of all the performing arts, magic is the easiest to learn because so much can be done with a simple effect," he told a visitor. "You take a simple thing -- here, let me get you to hold this just a minute. This is as simple as you get. A mother bunny and a daddy bunny -- put one in each hand. They're rubber. Feel them. See? Only two. Well, as I was saying, one practices, works hard at the craft, like anything, and if you practice, you prosper. Oops, I forgot. You're still holding the rubber bunnies. Just open your hand. And -- "he's laughing loudly as his guest opens both palms to find explosions of tiny babies falling between all the fingers.

Thomas' lifelong affair with magic began when he was six. His minister came to call and taught him how to float a needle in a glass of water. Not too much later, Thurston was appearing at Baltimore's Ford's Theatre. Thomas was called to the stage to assist in a trick. "And that was that," laughs Thomas.

By 1938 he had purchased a spot for his first store -- right down the street from his current location. Ten years later he moved farther down North Charles Street, in the meantime collecting his cherished valuables and building his trade.

A few summers ago, while he and Anne were out of town, fire destroyed the shop. For two months, friends and the Thomases sifted debris, sorted and cleaned the remains and got the shop ready to reopen at its new location on North Charles.

"I never knew I had so many friends, until then," he remembers now. "We came out of the ashes and started over."

Would he retire and sell his business? Spend more time performing and lecturing or teaching? "Ha!," he snorts, "Magic is life. How does a person retire from life?"

MAGIC MOMENTS: Yogi's Magic Mart is at 217 North Charles Street, between Saratoga and Lexington near the Charles Center in the heart of Baltimore. It's open Monday to Saturday, 10 to 5. "Yogi's Youngsters" is open to the public, every last Saturday of the month at 2. Admission 50 cents; if you get up and perform a trick, it's free. 301/727-5674.

WASHINGTON WIZARDRY: Here are some magic shops a little closer to home where you can stock up on tricks and expertise:

AL'S MAGIC SHOP -- 1012 Vermont Avenue NW. 789-2800. Magician Stan Cohen teaches aspirants the fine art of magic for $25 per hour-long, private lesson.

BARRY'S MAGIC SHOP -- 1123 Georgia Avenue. Wheaton. 933-0373. Owner and professional magician Barry Taylor gives private lessons and classes when his performing schedule allows.

DREAM WIZARDS -- 84 Halpine Court, Rockville. 881-3530.