It was the Chesapeake and Ohio Canal Association's 25th reunion dinner Saturday night. With about 40 others, Larry Hughes had just spent 13 days trekking 185 miles from Cumberland to Washington, immersed in the Potomac springtime and the veterans' tales of Supreme Court Justice William O. Douglas' 1954 hike and the long fight to save the old canal.

"What surprised me," he said, "is that it doesn't look like a national park."

He did not mean that the canal and river bank are too slender or ordinary to be preserved. What bothered him, he went on, was that this path through hills and history is not tended or explained as well as a national park should be. He had seen too many shacks along the river bank, too much debris, too many crumbling aqueducts and locks and virtually no educational signs.

The shacks are gradually being removed by the National Park Service or floods. The other points Hughes touched on - general tidiness, historic restoration, public services - are increasingly touchy subjects along the canal and throughout the national parks. At this year's C & O reunion, the park's future was hardly discussed; with no controversy roiling, most speakers indulged in recalling the past. But many questions are still unsettled, and much rescue work remains to be done.

One major mistake may be avoided. The canal may well be spared the kind of over-building that has cluttered many older parks. NPS has repaired parts of the towpath and put in scattered boat ramps, parking spaces and rudimentary camping areas. But more ambitious "improvement" notions have been squelched by tight budgets and loud protests from the official citizen's advisory commission, which includes some of the most energetic volunteer protectors of the canal.

Several years ago, the commission persuaded NPS to adopt an innovative zoning plan to leave the towpath's wilder stretches alone - untidy as they may be. The panel is now resisting proposals to expand the parking lots and other facilities on the Maryland side of Great Falls, which sometimes gets so crowded that cars must be turned away.

Some long-time hikers are even more vehement. One of them, Emmie Johns of Arlington, said Saturday, "I hope they never improve a single access road. If people have to try a little harder to get to the quet parts of the park, well, that's good for them."

So far, without being too restrictive, NPS has managed to maintain a generally easy-going ambiance and some reaches of solitude. Even on Saturday, near Little Falls, the towpath resembled a small-town park where the hikers mingled with neighborhood joggers, strollers, bikers and a small amateur orchestra that came to play during lunch beside a lock.

As a recreational haven, the canal is doing well. Yet it is a national Historical park - and the historical dimension, the real foundation of the canal, is not being tended well.

Time and weather are not the only threats to the old waterway's surviving features, especially its remarkable stone aqueducts. The NPS' all-or-nothing approach to restoration also hurts. The agency lacks the millions of dollars, the craftsmen and the engineering lore to rebuild all the aqueducts precisely as they were. So it has settled for propping up the most rickety ones without trying to preserve or echo the canal's 19th century style.

The official philosophy "is not to fool anyone," one ranger said unofficially. "If they can't do something totally authentic, they will do it in a deliberately unhistoric way instead of faking it."

In accord with that theory, one "stabilized" aqueduct now sports a brand-new railing of shiny aluminum. The remains of another have been buttressed in concrete and stone, much like the terrac of a posh shopping arcade. And the barge now used for canal tours is made out of concrete - although the mules are real. Some park officials are embarrassed by such incongruities, but apparently the design decisions are made somewhere else in NPS.

At least the ruins can be seen along the trail. But they are silent - and , as Larry Hughes noted, there are no signs. A visitor has to buy a guidebook to learn the most elementary facts about the canal's construction, its operations, and the lusty culture of its working days. Even more telling is the fact that when the agency's designers did propose the first set of interpretive signs last winter, some of the information included was wrong.

Such problems are more curious because the canal's history is hardly secret. Many documents and books exist. A number of nearby groups and individuals are extremely well-informed. Moreover, some former canallers are still around, although their ranks are dwindling fast. One of these erstwhile boatmen, George "Hooper" Wolfe of Williamsport, has become well-known. But htere are others, also mostly octogenarians now. One of them, J. P. Mose of Beaver Creek, said at the mid-hike dinner in Williamsport that he remembers a few things Wolfe hasn't told.

Surely more of this history - the heart of the park - could be collected, organized and widely shared. But the record so far suggests that NPS, left to itself, is not going to do the job very soon or, sad to say, very well. The canal's friends and neighbors should bestir themselves. It's not the sort of cause that prompts mass marches down the trial. But at least someone could pay a call on J. P. Mose. CAPTION: Picture, no caption, A 1914 photo by William Vetter