The Sweetness of a Pittsburgh Girlhood : AN AMERICAN CHILDHOOD<i> by Annie Dillard (Harper & Row: $17.95; 272 pp.) </i>

Toward the end of this endearing account of growing up in Pittsburgh, Annie Dillard writes a sentence that sums up its astonishing richness of detail: “It all got noticed.” Dillard is the Pulitzer Prize-winning naturalist, literary critic and writer of beautifully wrought prose. In “An American Childhood,” she demonstrates her gift of total recall and an eye that misses nothing, records everything.

The book begins when Dillard is 5 years old. With the shrewdness of a forensic scientist, and with her sense of humor already well formed, she hits upon the most important difference between children and adults. “Our parents and grandparents, and all their friends, seemed insensible to their own prominent defect, their limp, coarse skin.

“We children had, for instance, proper hands; our fluid, pliant fingers joined their skin. Adults had misshapen, knuckly hands loose in their skin like bones in bags; it was a wonder they could open jars. . . .” Obvious as this is to Dillard, who hides her revulsion out of tact, the decrepitude is lost on the ancient ones. “Adults were coming apart, but they neither noticed nor minded.”

Her affectionate tone here is the tone of the book throughout. If there’s such a thing as the perfect childhood, Dillard lived it--securely loved, given exactly the right amount of freedom, encouraged to indulge her limitless curiosity. In this sunny memoir, which reminds one of an Impressionist painting, her memories shimmer on the page.

Dillard’s mother is “kind, imaginative” and also fiercely principled. Not only that but she’s a beauty and a wit.

Her father is a romantic who succumbs to repeated readings of “Life on the Mississippi,” dozens of copies of which he owns, quits his job and heads for New Orleans by boat. Six weeks later, he turns around and comes home, disillusioned but undaunted. Lover of Dixieland, dancing and practical jokes, Frank Doak is one of the world’s enjoyers. Checking himself out in the mirror, as he gets dressed for a party, he can’t help breaking into “an anticipatory soft-shoe.”

Both of these charming people delight in language, Dillard’s mother speaking in a patois that suggests a one-woman vaudeville routine. “Her speech was an endlessly interesting, swerving path of old punch lines, heartfelt cris de coueur, puns new and old, dramatic true confessions, challenges, witty one-liners, wee Scotticisms, tag lines from Frank Sinatra songs, obsolete mountain nouns and moral exhortations.” Aha! the reader observes sagely, so that’s why Annie Dillard is such a language wizard: early childhood conditioning.

“An American Childhood” also explains why the poet in her keeps getting yanked offstage and supplanted by the comedian. At her parents’ knees, too, she learned to deliver a punch line; play straight man, “an honorable calling . . . despised by the ignorant masses”; appreciate sight gags, running gags and “the top of the line, the running sight gag.” When her parents manage to pull off the latter feat, she writes, their children heard tell of it just “as other children hear about their progenitors’ war exploits.”

With her two younger sisters, Dillard spends idyllic summers at her paternal grandparents’ house on the shore of Lake Erie. There the lifelong close observer notes the rivalry between the grandmother she calls Oma and her own mother. Their “long, civilized antagonism,” she comes to understand, is a form of class warfare.

Like her mother, the children look down on Oma for her terrible taste in household decor. The grandparents have lots of money, “an embarrassing Cadillac” and no aesthetic sense. Only later does Dillard reflect that “Matters of taste are not, it turns out, moral issues. . . . We thought that merely possessing a gaudy figurine was a worse offense than wholeheartedly embracing snobbery.”

In her family’s comfortable, sprawling house, with its “bright sunporch” and a glowing golden sandstone wall her mother designed, Dillard begins “a life of reading books, and drawing, and playing at the sciences.” This life she pursues with passion, as caught up in a book called “The Natural Way to Draw” as she is by sandlot baseball, hunting for buried treasure in the alley next door and constantly expanding the boundaries of her known world. Looking back on the explorations she makes on foot and by bike, she feels again what she felt then, time having heightened memory instead of dulling it. What joy and relief she felt, she writes, when she came home at night “exultant, secretive” from her latest ramble. “From the very trackless waste, I had located home, family and the dinner table again.”

The book describes her life through childhood and young womanhood, to the point where she leaves for college. In a Pittsburgh that seems the very essence of America, “a clean city whose center was new,” she grows up absorbing the sense of infinite possibility, along with plenty of calcium, in her bones. How typically American, too, are her cheerful optimism, her enterprise and her confidence that she can learn anything and master any skill if only she puts her mind to it.

The world is Annie Dillard’s oyster. The oyster is worth a course in marine biology, a series of drawings, a poem celebrating its place in God’s scheme of things. The world enthralls in its mysterious and cunning intricacies.

Loving and lyrical, nostalgic without being wistful, this is a book about the capacity for joy.