Georgie White Clark was 80 years old when she guided her last raft of tourists through the rapids of the Grand Canyon. It was the fall of 1991. She'd been swimming and boating those rapids since 1945.

Clark grew quite thin during her last summer on the river. She tried to blame her weight loss on the new Park Service regulations that prohibited boatmen from drinking on the job. Clark had been in the habit of punctuating each day with beer. She said the new regulation was stupid. She thought lack of beer was making her frail.It turned out to be cancer making her frail. In the spring of 1992, Clark sold her rafting company to Bill George of Western Rivers and wrote a letter to her customers recalling her 47 years as a river rat. She died that May.

In a new biography, "Woman of the River," Richard Westwood attempts to chronicle the life of one of the Colorado's greatest characters. He succeeds in describing her exploits, if not her motivations.

Clark was one of the first guides, and the first female guide, to take tourists down the Colorado River. With her World War II surplus rafts and her zest for adventure and her slide shows and self-promotion she opened up the Grand Canyon to thousands.

Westwood didn't know her, but he interviewed people who did. His book is a contribution to history. The only other book that's ever been written about Georgie Clark, she wrote herself. And like many colorful people, Clark exaggerated - probably even lied - about her life.

She told several interviewers that she grew up in Chicago, learning to swim in Lake Michigan. Westwood says she was born in Oklahoma and grew up in Denver. Early in her career, she defended the right of fellow adventurers to write about swimming rapids they really didn't swim. The reader can't help but remember her attitude toward accuracy while reading Clark's subsequent descriptions of her own adventures.

Nor was Clark given to introspection. Not long after she married her second husband, James White, she began spending weeks every summer wandering about with a fellow Sierra Club member named Harry Aleston. Westwood includes some of the notes Clark wrote to Aleston, during the winters between their treks. She talks about wanting to get a divorce from her husband and she talks about her time with Harry on the Colorado being the best time of her life.

The reader has to wonder. If Aleston had responded with encouragement, would Clark have left her husband? (White was already drinking heavily and may have even been abusive.) Instead, Clark spent many more years with White.

We don't know enough about Georgie Clark to understand what fears and insecurities kept this seemingly brave woman a captive to her marriage. Westwood doesn't explore the relationship with Aleston other than to quote Georgie saying they were just friends.

Westwood dutifully describes every rapid on every river Clark ever ran. But the reader wants to know more about Georgie. Westwood tells us just enough to tantalize.

We know Clark wanted people to think she was tough. We know it was also important to her to be able to say she'd never lost anyone on the river (even though she had).

These two points of pride came together in an incredible way, in 1989, when her employee and friend, boatman Marty Hunsaker, drowned on one of their trips. When the other boatmen caught up to her raft and told her, crying, that Marty was dead, she calmly commented, "Well he was a smoker."

Anecdotes such as that have made Georgie Clark a legend.

It would have been a much more ambitious biography had Westwood set out to discover what makes an eccentric become so eccentric. Because eccentric she was. Georgie started her career wearing odd little flirtatious outfits - leopard swimsuits and black lace bras. In old age she graduated to a full leopard bodysuit. With tail.

Another eccentricity: Clark refused to make a fuss over her guests. Let other river companies serve Dutch oven feasts on nice china, Clark's guests made do with cold cereal, boiled eggs, peanut butter and jelly, and steak served without a knife or fork.

But she loved the canyon and the river, and people who rode with her came away loving the canyon and the river - and often loving Georgie, too.

"Woman of the River" tells enough of Georgie Clark's life to make the reader fond of her also. Despite her meanness. Especially sweet is the photo of Georgie when she was an old woman, at the helm of her raft, bouncing sideways down a wave, and laughing and laughing as if it were the first time she'd ever run a rapid.