We are so uneasy with the rushing chaos of the life-river that we sometimes go to desperate lengths to order it -- or imagine that we do.

In the bar mitzvah (bat mitzvah for girls) you inform the world on your 13th birthday you were, a child, but today you are an adult . . .

Amy Elizabeth Saler of Wynnewood, Pa., will be 13 on Sept. 10, with her bat mitzvah to follow soon after. Her grandmother Hermione has written to hundreds of famous women all over the world, asking them to tell Amy what it was like to be 13.

So far she has had 150 replies. Many are simply signed photos, or form letters, or pleasant but general statements like Nancy Reagan's "I look back with fond memories of my teen-age years . . ." But at least they were interested: Princess Grace, Margaret Thatcher and Lady Bird Johnson; Sophia Loren, Mary Renault, Marta Casals Istomin, Melissa Hayden, Molly Picon, Ella Grasso, Jane Byrne, Kay Boyle and Mary Tyler Moore; Elizabeth Taylor Warner and Jean Stapleton and Lillian Carter, who noted that she too has a granddaughter named Amy, who will turn 13 October.

Queen Elizabeth and the queen mother and Mme. Sun Yat-sen all replied stiffishly through their aides ("I am commanded by the Queen to write and thank you for your letter"), and a few weren't sure what was wanted of them. But some wrote real letters.

"When I was 13," said fashion mogul Diana Vreeland, "I was being taught ballet by Fokine . . ."

"At 13 I planned to be a portrait painter," recalled consumerist Virginia Knauer. "I wanted to be a concert pianist," wrote singer Hildegarde, "but I never quite made it."

Opera's Licia Albanese remarked with charming modesty that on her 13th birthday she was asked to sing for her parents, "and it was then that they discovered I had a singing voice."

Some, like Iris Murdoch, couldn't even remember their 13th birthday. Some were bitter. Estelle Parsons wrote of an "alien world" and "cruelties of past and present," and Joan Baez added, "To be very honest, my 13th year was no picnic." And some were upset with the whole project.

"I don't know you and have never heard of you," wrote one indignant celebrity. "Since I am not Jewish, I cannot tell her anything about my bat mitzvah."

And someone else thought she was being invited to the party and refused, and another was angry because of the sexist notion that only women were being polled on what it was like to be a 13-year-old girl.

What is it like, then, to be Amy Saler, 12 going on 13, girl going on woman?

She lives well, very well, in a 20-room suburban house with an indoor swimming pool and sauna, and a beach house in Atlantic City big enough for herself, parents Richard and Barbara Saler, sister Susan 7, twins Stephanie and Alexandra, nearly 4, and the live-in help. And Homer the poodle.

She is short and slight like her grandmother, with extra-bright olive-black eyes and long black hair, and she is a little shy but looks right at you.

She is also very organized. Twelve-year-olds usually are.

"I get up at 10-of-7," she says, "and I listen for the weather on the radio, or if they don't have it, I phone in for it, and then I pick my clothes for the day, get my books together, wash and do my hair and come down to the kitchen."

She always eats the same breakfast: two pieces of toast (her mother insists on whole wheat or sourdough) and Cream of Wheat (no sugared cereals allowed). Her favorite breakfast is coddled eggs with mushed toast. Then she takes the bus to school at 7:35.

"Susan gets to take the 9:20 bus. I used to do that, she sighs. "Those were the days."

After school there are the snack of crckers and juice, the newspapers which she reads thoroughly, the piano practice and homework. She doesn't see much TV: Susie is the family addict.

Oh yes, the swim. Every afternoon when her father comes home, the whole family heads for the pool. At 39, he is the driving president of a worldwide sign advertising complex, and his daily 40 laps are what keep him going, he says.

His work takes him as far away as Africa, installing monumental sculpture for the Nigerian government, and before this he founded and built a food processing firm in Puerto Rico. And before that, at 13, he took his bar-mitzvah money, several thousand dollars, and started a golden retriever ranch.

His father, Harold B. Saler, is a prosperous attorney (and violinist), born in Philadelphia like his mother. His grandfather came from Russia at 17, sold milk from a cart, ran it up into 70 diary-product stores.

"I like my age in some ways," says the milk peddler's great-granddaughter. "You're not a child but not an adult. Parents expect a lot of you, yet indulge you."

Margaret Chase Smith: "Well do I remember when I was 13, the birthday party my mother arranged for me, my feeling that I was grown up and could do the things I wanted to do . . . Of course times will change, but even when you question the advice given you, your grandmother usually knows best as she is speaking from knowledge based upon actual experience."

In the pool, Amy watches over her little sisters even as she tumbles about with them. "I was 9 when the twins came, and I was ready to be like a little mother to them." She carries Steph around on her hip when we tour the grounds.

"Fight? Only with Susan, and lots. I named a doll Susan before she was born. Susan was so cute as a baby. She was always the wild one, and I was the quiet one."

Her eyes flare as she talks about Hebrew school, where she is learning the traditions and language so she can take her place in the religious community.

"We do the same amount of work as the boys, but they're so lazy, they don't care. When they mess up, nobody bothers them."

She tosses her mane. "The girls don't get to read the Torah, either. It's too holy for us to read.

Summers she goes to Camp Windhover on Cape Cod, an art camp where she does her piano and writes poems and choreographs dance. She took ballet at 4 but stopped after five years and now wishes she hadn't. "I used to be good," she muses.

School: She loves English, reads two books at a time ("The Agony and the Ecstasy" and "The King's General"), wishes she could have English class all day.

Does she like school?

"No one likes school." Delivered with finality: the wisdom of the ages.

Lucille Ball: "I didn't know what a teen-ager was when I was your age, but I certainly enjoyed it." Lucie Arnaz: "You're in for a sensational next 12 months!!"

"I want to help people," says Amy Saler. "I want to be a lawyer or social worker or teacher, maybe a librarian -- my father would be mad," she chuckles. "I plan to marry and have one child, I hope a girl. I'm not going to spoil her."

But she is bitter because she had to wait to be 11 before she got clogs, and Susan got them at 7.

She is a picky eater, her mother says fastidious. Makes her bed and cleans her room.

But the room is often messy. Shortly after her mother made a rule that clothes left on the floor would be confiscated, she left her best slacks standing brazenly in the middle of the room as though she'd jumped clean out of them. They were taken away.

"I think it was a message," remarks Barbara Saler. It bothers her that some of Amy's friends wear designer clothes to school and "totter around on high heels." A second child herself, she remembers to keep an eye on Susan's trials as second-born, so different from the problems of the first-born. She reminds Amy of all the years that she had her parents to herself, the exotic life in Puerto Rico, France, Mexico. h

"We went on a two-hour trail ride in Mexico," says Amy. "Susan had to be on a lead. I was on my own."

Phyllis George Brown , first lady of Kentucky, ex-Miss America: "When I was 13 years old I remember thinking it would take forever to grow up."

Amy says movies don't affect her much, but she loves to read the books they're based on. Her room has paired pie-slice windows like the the house in "The Amityville Horror," and it makes her a little nervous. Once she thought she saw red eyes in the night, but it was her sister's digital clock.

She writes poetry and stories. She likes words so much that she browses in a thesaurus. She goes to concerts with her grandfather, adores ballet.

It seems to run in the family. Barara was a painter before she married, and the grandparents' lush city apartment bristles with paintings.

Dame Flora Robson: "Remember that art which touches the heart is more inportant than just getting a vote. It can change the world and make it a kinder place."

What will it be like to be 13? She looks forward to the bat mitzvah and the huge reception after, the piles of presents, the money gifts. ("She'll give a quarter of it to charities, it's a family tradition," says her father, "but they have to be meaningful to her, she has to have a reason for the charities she picks.")

"I don't need a lot of money," says Amy. "Just as long as I have books. I think women should be equal, but I still like the idea of holding doors open for us."

Petite and neat, careful to scrub her smooth skin, ever watchful for blemishes (candy is rationed to once a week), she probably won't have the worries of some teen-age girls, like Lynda Robb, who wrote, "I was in junior high school in Texas, and I was taller than any of the boys in my class, and you wouldn't believe the crazy clothes we wore; we piled on petticoats until they made us look like the Pillsbury dough-boy . . ."

Perhaps it was Dorothy Storck, a columnist for the Philadelphia Inquirer, who said it best. She made a column out of it:

"Thirteen is a tough year, Amy because it is the year you grow up more than any other. Your body grows and changes and for a while doesn't seem to belong to you at all. Your mind seems full of doubts about who and what you are.

"You are no longer a little girl, not really, even though some adults still treat you as if you were. Yet you realize you aren't ready to be all on your own either.

"When you are 13 nothing much about you seems to be in the right place. Not your legs, which are knobby, or your hair, which flies away, or your teeth, which need braces. At least mine did. You are not in the right place with boys, either. The boys who were your friends in the fifth and sixth grades are suddenly awkward around you in the seventh . . .

"your are hurt a little by this, and seek out your girlfriends to compare hurts. This is when you first learn the value of women friends . . .

"There will never be another year for you quite like the 13th, Amy. Take from it the tender things."

And from Siobhan McKenna, the actress a photograph and two words: "Good luck."