Prodded by the American Society of Civil Engineers and other citizens, the National Park Service is finally starting to preserve the romantic reminders of the country's first perilous trade route of the West - the "Potowmack Canal" on the Virginia side of the Great Falls.

It was George Washington's dream - which, in the words of one historian, "hovered closely to an obsession" - to force the link across the Alleghenies by making the Potomac navigable as far as Cumberland and moving goods by road over the mountain ridge to the streams that flow into Ohio.

The most awesome obstacle to river boats was (and is) the 76-foot drop of the Great Falls, one of the most picturesque cascades in the world.

The Potowmack Company, founded in 1784 with George Washington its first president, built a canal to bypass the Great Falls and lift or drop boats in a sequence of five canal locks.

It was a remarkable engineering feat for its time, a time when few Americans had so much as seen a lift lock before. The drama of daring and defeats and of dogged persistence spun out over 17 years. The dramatis personae were remarkable

There was the determined George Washington who gave much of his time and energy to the project for 30 shillings a year (about $7.50 at the rate prevailing at that time). There was swaggering "Light-Horse Harry" Lee, father of Robert E. Lee, who named the canal company town after his beautiful young and extravagant wife, Matilda (Lee's nickname derives from the fact that as a cavalry officer he saddled his troop's horses as lightly as possible so they could move fast.)

And then there was a cast of hundreds of unruly slaves and indentured Irish and German servants who were bribed to meet their work quota with extra portions of rum and punished for absenteeism by having their heads and eyebrows shaved.

The hero in the drama, of course was the erratic and willy river with its rocks and rapids and unpredictable pranks. It triumphed in the end. The toiling men, with their rum and their dynamite, could not even clear all the ancient "fish pots," the rock dams that interfered with boating. Archeologists now conjecture that the "pots" were built to trap fish by Indians some 6,000 to 7,000 years ago.

In 1821, the Potowmack Company gave up, although it had managed to move considerable quantities of furs, whiskey, flour, lumber and pig iron from the western parts of Maryland and Virginia to Georgetown. But not at a profit. Lotteries, the favorite form of public subsidy at the time, did not help. Further financial aid, the Maryland and Virginia legislatures decided, seemed "imprudent."

It seemed wiser to build one continuous canal rather than tame the Potomac. But the Virginia experience undoubtedly helped the engineers of the Chesapeake and Ohio Canal on the Maryland side. The C&O Canal was begun in 1828 - shortly after the Erie Canal, connecting Lake Erie with New York City, had launched America's canal age and, with it, industrialization.

All this is in books.

The ruins of the old Potowmack Canal locks and of Matildaville, which make this glimpse of our history real, visible and vivid, are in deplorable condition. Since 1960 they have been in the custody of the National Park Service as part of the 800-acre Great Falls Park (five miles form Exit 13 of the Capital Beltway on Va. Rte. 193 and Old Dominion Road).

The Park Service has provided an attractive, modern visitors center, parking, picnic benches and information signs. It also displays and instructive model, showing how the old canal worked. But to the chagrin of civil engineers and many local historians, it has done nothing to date to arrest galloping damage to the venerable, old stones of the locks.

There has been much vandalism. The houses of Matildaville and some of the canal walls of beautifully dressed and fitted red Seneca sandstone obviously serve as an illegal quarry for new construction.

The roots of unwanted trees and a jungle growth of other vegetation is cracking and crumbling the old masonry work. Nature is reclaiming what man has wrought.

With many demands and scant funds to meet them, the Park Service first hoped to appease the Potowmack Canal enthusiasts by "stabilizing" the ruins. It was simply going to fill in the crumbling stone gullies and thus make them safe. The justification was that it could all be dug up again at a more propitious time when there was more money.

Citizens and some history buffs within the service protested that "out of sight" would soon mean "out of mind," that we cannot just bury a part of history.

So now the Park Service has obtained an appropriation of $700,000 for the project, $200,000 of which will be used for an engineering study by a private firm in Roanoke, Va. More funds are to be requested.

The present plan, according to Ed Duffy, who, with a staff of a dozen men, runs the Great Falls Park, calls for "selective repairs."

No one is thinking of restoring the canal, the way the C & O Canal has been restored, so that it could gain move gondolas and sharpers (long narrow boats) as of old. That would be enormously expensive and a little phony.

Instead, we can now hope for a gradual restoration of the ruins to the state they were in a few decades ago, a state that would show us how the canal worked and give us an impression of this heroic accomplishment. It would be a sort of monument. As people see the beauty and archeological interest of the site, the Park Service hopes, they will want to see more and urge Congress to provide the funds.

Duffy also hopes that the Youth Conservation Corps and other volunteers might pitch in with putting old stories into place and pushing back the jungle. Fairfax County high school archeology students have offered their labors.

It is not just a matter of rescuing our past. Making the past part of the future is what civilization is all about.