DOWN on Washington's Mall stand the great museums of America, collectively known as the Smithsonian Institution: Air and Space, American History, Art (in several modes), and Natural History. The last building draws over 5 million visitors a year, who come to see the splendors of our animal, vegetable, and mineral world.

Guarding the rotunda entrance is an immense African elephant, eight tons of hide, tusk, and uprearing trunk. The elephant is a proper introduction to natural history. In the old Hindu fable, six blind men approach an elephant and -- touching separate parts of its anatomy -- declare it to be a wall, a spear, a snake, a fan, a rope, and a tree.

Students of natural history face a comparable problem, as they attempt to infer the vast shape of life from scattered bits of matter. Rocks reveal the staggering depth of time; the fossils imbedded in rock commemorate thousands of long-vanished species. Natural history is one of our bolder acts of knowledge: through it we dare to imagine an earth that men have never actually seen.

To build a Museum around these themes is a great challenge; to compress some 20 acres of exhibits and collections into a single volume is a task beyond the resources of most words and pictures. But Messrs. Kopper, Sandved, and Clark have worked their own inferential magic. They have created a book that is a museum itself, one that displays and interprets that building on the Mall as visitors will never see it.

We can only imagine the problems faced in assembling this book, for the final product is a work of sumptuous beauty. Printed on heavy stock, in clean typography, the pages gleam with iridescent color. The photos are accurate -- but heightened by a stylish sense of design. Many were shot in extreme closeup, against a dark background and with low-angled light to accentuate relief.

The camera yields images of nature that are also works of art. Orchids give way to ceremonial masks, rainbowed snails to lustrous gems. Yes, a requisite picture of the Hope Diamond appears, but far more beautiful is the expanding spiral of a chambered nautilus. Other pages tell stories: a drawer contains birds collected by Audubon, Darwin, and T. Roosevelt; Museum artisans recreate a life-lized pterosaur, world's largest flying reptile.

As might be expected from a Smithsonian venture, this book is not simply a garden of visual delights. Philip Kopper's text is substantial and lucid, each chapter an essay on the things we are seeing and the ideas they represent. His version of Museum history is a lively colloquy of fact and gossip (naturalists are prize eccentrics); while his accounts of scientific procedure are models of clear exposition. At times he may work too hard at defending pure research, as though he fears some readers will scoff at exacting studies of flies and beetles.

Kopper's greater challenge was to find a plan for his book, since neither the Museum nor the field of natural history is wholly systematic. Begun as a "National Cabinet of Curiosities" in the 18th century, the Museum grew like Topsy, in unplanned spontaneity. Kopper wisely divides this labyrinth into many museums (Science, Art, Earth, Life, Man), then he demonstrates that research, exhibits, and collections constantly spur internal development. For him, this process defines the Museum's identity: "Its growth, its very being, have always been organic."

The same qualities explain why this place is called a "National Museum," when its collections cover the world -- and parts of outer space. For the Museum is a mirror of America, a country ever-hungry for facts, for discoveries made through exploring. for the gathering of incongruitites under a single roof. "A literal example of E Pluribus Unum," Kopper calls the Museum; one can imagine Walt Whitman smiling in agreement, could he turn these pages today.

The whole earth and its forces are here, for Americans to see and understand. The most powerful image in this book is of a pair of hands, powdered with dust, slowly carving away the rock that surrounds a fossil skull. The past gives birth to us, but we are also its midwives.