Surrounded by files and boxes - "amoeba to chemical," "salt marsh to zooplankton" - Ruth Patrick bends her head to peer into the microscope.

"Ah, here," she says with a smile of satisfaction. "They're small, but they're lovely."

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They are, to her, "my diatoms."

One-celled algae - as elegant and ornamental as snowflakes - that are present in virtually every body of water, they launched her career, cemented her renown, and defined her life.

At age 99, Patrick is still working with them.

A woman who has sloshed about in waterways all over the world hung up her waders less than a decade ago. But she still comes to work every day at the Academy of Natural Sciences, whose doors she first entered in 1933. From down the hall she calls to her assistant, "I'm here!"

Decades ago, long before pollution became a public concern, Patrick discovered that diatoms are prime indicators of water quality because the cells' silica walls so readily absorb pollutants.

"You see," she says, "diatoms are like detectives."

She also devised a model - known as the Patrick Principle - for gauging the health of a body of water by evaluating all the life in it, from diatoms to insects to fish.

If this sounds familiar, it is because Patrick pioneered an ecosystem approach that now is common knowledge.

Fittingly, her legacy is everywhere.

Just walking to her office, she passes a sign: Patrick Center for Environmental Research. It is the newer name for a department she founded in 1947, two years after finally being put on the payroll when a wealthy industrialist heard one of her presentations and raised the money. The center's nearly 20 researchers continue her work on watersheds.

A science building at the University of South Carolina is named for Patrick, too. And the Ruth Patrick Set-Aside Area, a protected marsh near Aiken, S.C., honors the baseline surveys she conducted in the 1950s before DuPont Co. built its Savannah River nuclear plant nearby.

She's been showered with honors, summoned by presidents.

Lyndon B. Johnson asked about water pollution. Ronald Reagan sought input on acid rain. Bill Clinton presented the National Medal of Science.

Thomas Lovejoy, president of the Heinz Center for Science, Economics and the Environment in Washington, wonders if even she grasps the import of her work. "It laid the foundation for environmental science and environmental management today."

Patrick shrugs off the acclaim. "I try not to think about it."

"Dr. Patrick." That is how the academy staff addresses her.

Talking among themselves, however, they use the affectionate moniker "RP."

Entering his first staff meeting on Feb. 1, the academy's new president, Bill Brown, walked up to Patrick and kissed her. The cafeteria staff insists on carrying her lunch tray.

She eats, often a hot dog and soup, surrounded by the chatter of class groups, all unaware that much of what they have learned of stream biology, or are about to, started with the grandmother in their midst.

Yes, she walks tentatively. She aches. And sometimes she forgets. But she remembers, too.

"At night, my father, who was a lawyer and fairly well to do, would roll back the great wooden doors of the library and go in and open his rolltop desk. And if I had been a good girl, I could climb on his knee and peer through the microscope."

Soon, he gave her his own boyhood microscope. She spent hours sprawled on the family's dining room floor in Kansas City, Mo., "looking at everything I could," much of it bounty from countryside jaunts with a collection can swinging by a string from a stick.

Her father encouraged her to go to college, and she enrolled at the University of Kansas. "But my mother was horrified I was going out with boys whose parents she didn't know."

Patrick transferred to Coker College, a small girls' school in South Carolina. A professor took an interest and sent her to the famed Woods Hole, Mass., marine biology lab.

She began at the academy in her mid-20s. "A little peon," she says with a sly grin: the unpaid assistant curator of microscopy. Every week, wealthy men who had formed a microscopic society would roll up in their chauffeured cars. She had to prepare the room for the group, although the men insisted she not touch their microscopes.

No other women were at the academy. Patrick wore pants to blend in, and she was once chastised for wearing lipstick.

"But I was determined," she says. "I was going to get my Ph.D. and I was going to write my thesis on diatoms."

She's added more than two dozen honorary doctorates.

For more than 35 years, she taught botany and limnology (the study of streams) at the University of Pennsylvania. Those who didn't drop out from exhaustion were magnetized by her sheer love of science. So many were influenced by her that Harvard entomologist E.O. Wilson called Patrick "the den mother of ecology."

She emphasized field work, which meant that on any given Saturday the class would be hip-deep in a stream, checking out nutrients in the Red Clay Creek or acid mine drainage in the Lehigh River.

Bernard Sweeney took her course three decades ago. "I'm 21 years old and here's a 64-year-old lady," he recalls, "setting the pace."

Today, Sweeney is president of the Chester County-based Stroud Water Research Center, known internationally for its work on streams and rivers.

An oil painting of Patrick sitting on a rock in the Susquehanna River hangs in the conference room. When Stroud staff meet to discuss a new project, "inevitably someone will say, 'Now remember, Ruth's looking at us. So we have to get this right,' " Sweeney says.

Carol Collier was another student.

Studying under Patrick "was so personal and intense," says Collier, executive director of the Delaware River Basin Commission.

Collier still doesn't know how Patrick did everything. Besides teaching and research, she advised environmental agencies and industry, often convincing some executive or other that he just had to join her in the stream.

Inquirer society columnist Ruth Selzer did so in 1956. "The night after she waded into the Brandywine, she was dancing on the Delaware," Selzer wrote. "Instead of hip boots, she wore diaphanous green chiffon."

In 1975, Patrick became the first woman and the first environmentalist appointed to DuPont's board of directors.

"Just a charming, remarkable person," says former CEO Edgar S. Woolard Jr., who began an environmental push at DuPont in 1989, partly due to her influence. "When she spoke up in the boardroom, whether it was on the environment or business, everyone listened. She just had that kind of stature."

Patrick has lived in Chestnut Hill for decades. She and her first husband, Charles Hodge 4th, a Temple University professor and authority on grasshoppers who died in 1985, raised a son, now a physician in Kansas. Her second husband, attorney Lewis H. Van Dusen Jr., died in 2004.

Hodge once remarked that being married to Patrick, who used her maiden name professionally at her father's request, was "like being married to the tail of a comet."

In June, the American Philosophical Society will open an exhibit, Undaunted: Five American Explorers, 1760-2007. It starts with David Rittenhouse and ends with Ruth Patrick.

Two of the artifacts the society has requested are the white pith helmet Patrick frequently wore in the field and the prototype of a device she invented - a diatometer.

Now standard equipment in water research, it's basically a floating rack of slides for diatoms to grow on. The original model, immortalized in climate-controlled storage at the academy, used toilet-tank floats.

Patrick has told friends that, factoring in her lifestyle and the life spans of her parents, she should be good to 109. Time enough, perhaps, to finish yet another book - the sixth volume in her series on American rivers.

"As you get older, you don't do as much as you used to," she says. "But I keep going."

Collier and Patrick still go out to lunch. "She's still on top of things," asking Collier what she thinks about some proposal on the Delaware or "how global warming will affect salinity models."

A month ago, the academy, which touts itself as "the oldest continuously operating natural history museum in the Western Hemisphere," celebrated its 195th anniversary. As the staff party ended, its oldest continuously operating biologist rose and, leaning on a cane scarred with use, headed back to work.

Out in the hall, a bird specimen in an exhibit case, a black-winged lory, caught her eye.

She bent to examine it, then turned, eyes shining.

"Fascinating, isn't it?"

The Patrick Principle

In the beginning

Ruth Patrick's work with microscopic algae known as diatoms taught her that the number and kinds of species present in the water reflected environmental conditions in general - and pollution in particular.

The big picture

She realized that this concept could be expanded to include all the organisms in a stream, from bacteria to macroinvertebrates and fish. Instead of a "snapshot" in time provided by a chemical analysis of a single sample, the creatures that live in the water are an indication of conditions over a long period of time.

In her words

"First you have the bacteria. Bacteria and fungi tackle wastes. Then you have the algae that consume the products that they produce. Then other organisms eat the algae. And there's a whole list of those, invertebrates of various types. Then, of course, there are fish that feed on these invertebrates.

"So you have an ecosystem. And I was the one that devised the ecosystem approach toward understanding the effects of pollution."

The goal

"My great aim," Patrick says, "has been to be able to diagnose the presence of pollution and develop means of cleaning things up."


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Contact staff writer Sandy Bauers at 215-854-5147 or