DENVER, SEPT. 12 -- Rarely is an institution as prosaic and prolix as Congress moved to commit an act of poetry, but that unlikely phenomenon did occur when the members passed Public Law 88-577, a lyrical piece of legislation popularly known as The Wilderness Act.

This revolutionary statute set aside millions of acres of the United States to be the permanent domain of natural forces, protected forever against encroachment by the machinery of mankind. The mood that swept the Capitol when the law was passed is reflected in its statutory definition of "wilderness," arguably the most poetic passage in the U.S. Code: "A wilderness, in contrast with those areas where man and his own works dominate," the law reads, is "an area where the earth and its community of life are untrammeled by man -- where man himself is a visitor. . . an area retaining its primeval character and influence."

In the 24 years since the United States adopted its Wilderness Act, however, the idea of permanent natural domains has been slow to catch on in other lands. But this weekend, at the World Wilderness Congress here, conservation leaders took a major step toward worldwide implementation of the wilderness preservation ideal.

The first worldwide inventory of the Earth's remaining wilderness, prepared by American conservationists Michael J. McCloskey and Heather Spalding, was distributed to delegates from 50 nations to help them institute preservation efforts.

The "reconnaissance-level inventory," a preliminary listing developed from the U.S. Defense Department's maps of the world, shows that almost one-third of the Earth's surface -- about 12.4 billion acres -- remains in a natural state essentially untouched by modern man.

Within national borders, the Soviet Union has the largest total acreage of wilderness, followed by Canada, Australia, Brazil, China (including Tibet), Greenland, Algeria and Sudan. The study says Greenland is 99 percent wilderness.

Although the United States has legally protected about 450 land areas under the Wilderness Act, the nation barely registers on the world inventory. McCloskey, the chairman of the Sierra Club, said this is because his preliminary inventory was restricted to plots larger than 1 million acres -- slightly smaller than Delaware. The Wilderness Act allows the designation for blocks as small as 5,000 acres, roughly the size of the Southwest quadrant of the District of Columbia.

The only parts of the United States that made the list outside of Alaska were the Bob Marshall Wilderness in northern Montana and the greater Yellowstone region of Montana, Wyoming, and Idaho.

If he could have included wilderness areas as small as 100,000 acres, McCloskey said, his world total of wilderness would definitely have been larger. "But it is impossible to know whether it would have been 10, 20 or 30 percent higher," he said.

In an address to the world congress, McCloskey said the preliminary inventory, prepared in the Sierra Club's Washington office, represents "the first time in history that humanity has been able to look at how far it has gone in subjugating the Earth and bending it to its use."

He urged nations of the world to preserve remaining wilderness lands "to maintain some measure of balance between man and nature." The inventory suggests that about half the wilderness lands on Earth are "self-protecting," that is, so hard to get to or so forbidding in terrain and climate that man is uninterested in developing them. McCloskey said the remaining wilderness needs legal protection, or it will become part of man's domain.

Barry Flamm, of the Wilderness Society, a U.S. representative at the world congress, said the principle set forth in America's Wilderness Act "hasn't been real well exported." He said some English-speaking countries, including Canada, Australia and South Africa, have taken steps similar to the Wilderness Act, but most of the world has not.

This is the 4th World Wilderness Congress and the first held in the United States. The delegates met in Denver this weekend and will proceed to Estes Park, Colo., on the edge of Rocky Mountain National Park, for the remaining five days of the session.