The water rushes over the whirling blades of the turbines, spinning them faster and faster, their soft hum rising.

Then the generators kick on, whining like the engines of a 707 at takeoff. The floor begins to tremble. The noise deepens, quickly drowning out conversation in a roar that tells the history of this woodland creek.For almost 200 years, man has bent this part of the Buck Run to his will, using the 14-foot waterfall to power mills that produced paper, steel and iron.

Now a couple here in Chester County, in southeastern Pennsylvania, is continuing that tradition.

In November, Don and Joan Silknitter went on line with Philadelphia Electric Co., selling electricity from the small hydroelectric plant they built near their home on Buck Run in West Marlborough Township.

Their private power plant not only generates enough electricity to run their household, but earns them a neat profit from PE. They're PE's only residential supplier of water-produced electricity, pouring their excess power into the company's giant grid.

We're just doing what was always done here - using the water power, Joan said.

In fact, the gray-and-white building that houses their machinery is a reproduction of the mill that stood there about 200 years ago.

Isaac Pennock built the first rolling and slitting mill in the United States at this picturesque site, situated about four miles south of Coatesville, in 1793. He named it the Federal Slitting Mill, showing his pride in the United States' newly won independence from England.

Mr. Pennock's mill, where sheets of iron were cut or slit, produced iron

from which barrel hoops, wheel rims and other products were forged, according to Coatesville historian Eugene DiOrio.

The mill eventually burned. It was followed by a series of others, all built on the foundations of the first.

The Silknitters didn't intend to advance that heritage when they bought the land in 1980. They wanted the property, named Rokeby by one of Mr. Pennock's daughters after a novel by Sir Walter Scott, so that their children would have more room to play.

But their plans changed when they heard a neighbor talk of a dream he never realized - channeling the power of the small stream. Slowly, his dream became theirs.

Don Silknitter began a yearlong excavation at the site that unearthed a trove of rusted tools, ink bottles, bullets and even shoes. As he cleared the thick trees and vines, the stone ruins of a long-abandoned mill emerged, hidden in the overgrowth like a forgotten fortress.

He found a century-old turbine buried in the mud. That crusted chunk of metal was cleaned and put to work in the new plant, helping to produce electricity and providing a link with the mills of the past.

Mr. Silknitter, a fifth-grade teacher at Unionville Elementary School, had no training in engineering or power production. But he had a long history of tinkering. As a boy, he took apart clocks and toys to see how they worked. As an adult, he worked on his car engine and installed the plumbing in his home.

He was sure he could build a power plant if he set his mind to it.

His brother, an engineer, worked on designing the plant and brought in friends to do the electrical engineering. Other friends of the Silknitters helped with the wiring and welding.

I did most of the work myself, Don Silknitter said. It's like the guy who climbed Mount Everest. Why did he do it? Because it was a challenge.

Parts were purchased new, such as a $12,500 turbine, or scrounged. The nozzle from an old fire truck made a perfect air vent, and an aircraft landing motor was used to control the flow of water over the turbines.

In the beginning, PE officials were less than excited about the plant, the Silknitters said. They'd had so many people say they were going to do this, and they never followed through, Don explained.

But as construction progressed, PE's line workers became more and more interested. They started calling the small plant Peach Bottom Five, after PE nuclear power plant.

The plant can produce a maximum of 5,376 kilowatt-hours a week, which sounds impressive but is actually an infinitesimal fraction of the power produced and sold by PE. The electric giant kicks out 664 million kilowatt- hours a week, sending that power to 1.4 million customers in eight counties and two states, according to PE spokesman Bill Jones.

The Silknitters earn 3 cents for each kilowatt-hour of electricity they sell. (A kilowatt-hour is the amount of electrical energy consumed when 1,000 watts are used for one hour.) They say it will be several years before they get back their investment.

But for them, money was not the issue. They're energy independent, so long as water runs through the valley as it has for at least two centuries.

Their lights burn steadily, illuminating a home filled with artifacts

from ancient iron and paper mills. Outside, water flows quietly past their door, spilling over the falls and heading downstream.

Everything goes in a cycle, Joan Silknitter said. Hopefully, the history of the property isn't finished.