Tucked away in a windowless storeroom that heats up to 88 degrees on a summer day, the federal government's Merlin of Minerals counsels the powerful and divines the future of copper, lead and zinc.

Bob Reiley joined the Commerce Department in 1976 after 12 years in the copper industry. Just five years ago, at the age of 30, he was responsible for the $100 million worldwide sales of the fifth largest copper company in America. He sat in a New York City executive suite overlooking the Rockefeller Plaza skating rink, with two secretaries at the snap of his fingers, Persian rugs beneath his feet and his elbows resting on a walnut desk.

"I wasn't out schlepping Tupperware," he says.

Now Reiley spends his working hours in a storeroom. His desk is vinyl, the floors are linoleum, his secretary sits just on the other side of a shaky partition. He often wonders why he's there.

"I'm not a bureaucrat yet, but I'm getting there," he says, wryly.

Reiley is one of nearly 100 industry experts employed by the Commerce Department's Bureau of Industrial Economics to keep tabs on the 200 major industries listed in the standard industrial code. More than 60 percent of them left private sector jobs for the Civil Service.

Kenneth M. Brown, the bureau's deputy director, says they are essential to the development of any of the industrial policies touted by politicians.

"Only the true expert can grasp which regulations we need to ease up on and which are necessary. They can also help pick out arriving industries," Brown says.

The bureau's experts cover steel, construction, automotive, processed food, retailing, farm machinery, oil and gas drilling, data communications, drugs, plastics, cosmetics and many others.

Why do these people leave lucrative futures for government service? What do they think they will get out of it for themselves? Do they plan on staying for long? What is a businessman's view of how the government works?

Reiley talked recently about his decision to sign up with the government and his impressions of how it works.

When the man who is now his boss called five years ago to offer him a job, Reiley paused for 10 seconds and said no thanks.

"What would I have been giving up? Money," he says.

But on his dreary two-hour commute to Long Island and his wife and kids he began to reconsider.

"I had to think hard about what's important in life," he says.

Several factors weighed in the government's advantage. First, he hated the four hours he spent every day commuting. Second, his wife's sister lives in Washington, and so his wife liked the idea of moving.

And finally, he thought he could "figure out how the system works" in a couple of years. "In the back of my mind I said I can always go back. I didn't count on liking what I'm doing," he says.

He also thought closely about how much money he would be sacrificing, and decided it wasn't so much. "What I was giving up was the potential to make a lot of money," he says.

Deputy Director Brown confirmed what Reiley says about the government's capacity to attract people from the private sector.

"We're not hiring the corporate vice presidents. Nobody is going to give up $150,000 a year to come to the government. But government salaries are competitive for midlevel corporate employees," he says.

After five years at Commerce, Reiley has no plans to leave Washington anytime soon. His wife likes Reston, their home now, and Reiley gets great satisfaction from coaching soccer for his four sons and their neighborhood team -- something he never had time for in New York.

Reiley also enjoys certain aspects of his job. He's not motivated by abstract ideas of public service, or by a desire for power. (He's laughing now.)

He does like the detective work he gets the chance to do every now and again. He refused to describe on the record specifically how he has assisted the Defense Department and the CIA, but he did say the work he does for them is exciting on occasion.

He helps the CIA, for example, figure out who is buying what metals from whom. Berryilium, used in making nuclear weapons, is under his jurisdiction, as is brass, used in making ammunition.

He also has more mundane tasks. He writes updates on conditions in his industries for the bureau's biweekly business conditions report, distributed only within the government, and he writes sections of the bureau's annual publication, the U.S. Industrial Outlook. Occasionally he writes testimony for congressional hearings.

He gives advice to government agencies devising and implementing metals policies.

Reiley likens government decision-making to that of the corporate boardroom.

In government as in business, he says, the president listens to his different departments and then makes his own decision.

Reiley says he offers a business perspective, while others offer environmental, public health and labor viewpoints.

"It would be ridiculous for the government to make policy without access to somebody who know it inside out," he says.

Dispite his jaunty, slightly defiant air, Reiley has his doubts.

Backed by posters of John Belushi and Mickey Mouse, symbols perhaps of his attempt to survive a ponderous bureaucracy with a sense of humor, he admits to some anger and frustration.

Believing that the government overregulates the minerals industries, he feels like a victim sometimes.

"People say, Christ, this guy is nuts. He's an exploiter. He doesn't care about pollution. Gripes the hell out of me," he says.

"You gotta dig up the ground, and it ain't pretty. And you gotta throw smoke in the air, you gotta do it," he says.

Otherwise, he says, the United States will be depending on small, unreliable countries for its key mineral resources.

"Most of the time you wonder if anyone listens or cares. Does what I do really matter? I don't know."

But after suffering through three reorganization of his office, he is not completely discouraged.

An ambitious man, he will keep plugging with the government for as long as he can move ahead. But he will quit when faced with the prospect of being the kind of bureaucrat cartoonist love to draw -- fat and lazy and dumb.