During more than 120 hours of experiments in a university lab in St. Louis, two young men performed amazing feats.

They bent dinnerware, moved objects without touching them, spun rotors protected by glass-covered cases, moved the hands of watches and made a digital watch go haywire. They saw through shielded envelopes. They made tiny fuses burn out suddenly, they created weird images on film.

All were fakery.

More than three years after the beginning of the experiments, magician James Randi exposed the feats as one of the slyest scientific hoaxes in years.

Randi said he masterminded the hoax to show that scientific research on psychic powers is not as scientific as it should be and that psychic researchers refuse the help of magicians to design experiments that prevent fakery.

Physicist Peter R. Phillips, director of the laboratory where the hoax occurred, said that he trusted his research subjects completely and feels "there are ethical issues involved" in lying to researchers. At one point, he said, he was "80 percent sure" the psychic powers of the young men were real.

Now he says, "I should have taken Randi's help earlier," but he added that he was glad that in the end "we never made any conclusive claims" in print about the psychics. From now on, he said, he doesn't intend to accept psychic subjects from out of town and will check the background of those subjects with whom he works.

Many experiments in psychic research have been "entirely too lax," said Robert Morris of Syracuse University, one of those most respected by believers in psychic research. Helmut Schmidt of the Mind Sciences Foundation in Texas, another researcher respected in the field, agreed that "most parapsychological research is not the tightest possible research."

With arguments aside about methods and ethics, both Randi and Phillips now agree: the hoax was worthwhile. It should put future researchers on their guard.

The hoax, which was revealed in the March issue of Discover, a science magazine, began in November, 1979, when two young magicians showed up, separately, at Washington University's McDonnell Laboratory for Psychical Research, each claiming to be a psychic of great power.

The scientists at McDonnell, after observing the magicians bend forks over dinner the first night, accepted their story and began running the two through scientific experiments to test their powers.

At times, the magicians said, the whole hoax was in danger, and one missing staple almost ended it.

In that experiment, magician Michael Edwards, now 23, was given specially insulated envelopes and asked to describe the pictures inside. The envelopes were closed with staples, and Edwards was sent alone into a quiet room "to concentrate" on the images.

He quickly pulled out the staples, looked at the pictures, replaced and rebent the staples to look the way they had originally.

But to his horror, "I dropped one of the staples," Edwards said. "It was dark in the room. And I just couldn't find it." When he left the room he was sure his career as a psychic had ended.

Thinking quickly, just before the envelope was opened, Edwards spoke up. He asked for one more "feel" of the envelope. He held it a moment, put on a concentration act, then announced its contents and ripped open the envelope himself so the missing staple would not be detected. The episode was scored as a psychic "hit", he said.

There were other times when the experiments were changed and the magicians had to invent new tricks on the spot, or suddenly claim "bad vibrations" and beg off the experiment.

But early on the hoax seemed to be working.

Physicist Phillips, the chief scientist at McDonnell, says he was taken in for a couple of years. But finally, after hearing a rumor that the young performers were fakes, and accepting some help from Randi, the experiments were tightened up considerably.

Suddenly, the psychic powers he had seen for two years vanished.

The whole scheme was cooked up in 1979 by Randi, the stage name of James Zwinge, the magician and indefatigable hunter of psychic fakery. To make it more interesting, Randi worked both sides of the trick.

On the one hand, he sent the two magicians to Washington University, which had been given funds to set up the McDonnell laboratory specifically to run psychic claims through a battery of rigorous scientific tests.

And on the other hand, he also sent 22 letters to those being hoaxed warning against the young men's tricks, offering to help, and suggesting specific methods of catching fakery. He instructed the young men that, if they were ever asked directly whether they were faking, they should admit it immediately. Phillips never asked directly, Randi said.

Phillips said he does not feel foolish or cheated by being the object of a hoax, but "exhilarated" because in the end he did not publish any wrong final scientific papers and finally reached the proper conclusion.

It was a very near thing, however.

The early report said, "Two apparently powerful subjects . . . have presented themselves to McDonnell Laboratory for Psychical Research . . . . Both experimenters Phillips and Mark Shafer have observed apparent psychokinetic metal-bending on numerous occasions, with and without contact by the subjects. In Phillips' first session with Michael Edwards, he and three others each in turn placed several straight keys in their closed fists and asked Michael Edwards to influence them . . . . Edwards was never allowed contact with the keys, and in each instance, when the hand was opened one of the keys was discovered bent."

Edwards said that he simply picked up the keys when attention was diverted and bent them.

Phillips wrote, "Both subjects seem able to affect photographic film to the extent of producing streaks or blotches of light." The magicians said they simply lifted the lens cap and snapped pictures when the experimenter's attention was diverted.

Phillips also wrote of the bending of a 1/16-inch metal rod that was laid in a lucite mold. When in the mold, "The rod can be touched but not so that one can physically influence it." The young magicians "physically influenced it" by bending it before it was dropped into the mold, they said. They held it at an angle that made it look straight, and with mystical mumbo-jumbo gradually rotated the rod so it appeared to be bending.

Randi's code name for the whole hoax was "project alpha". Now, he warns psychical researchers, a "project beta" is already under way. After beta, "I can go right down the alphabet," he said with relish.