This city marks the end of a stretch of the Potomac River known as the Smoke Hole, for reasons obscure.

"There's two theories," said Gil Miller, who runs canoe and raft trips out of Seneca, W. Va. "One is that it got its name from the smoke that seems to hang in the high ridges." He pointed to a sheer rock face of shale, whose barren top was shrouded in mist.

"The other is that there's a cave around somewhere that the Indians and later the settlers used to smoke their meat. But we don't know where that is."

The Smoke Hole Canyon is wild country, running 16 miles from a place called Big Bend, now a campground, to this small outpost in the mountains. It's obscure and isolated, with no road in or out. For that reason it stood for years as a bastion for moonshiners.

One of the score of paddlers Miller was leading down the river Sunday raised a suggestion. "Could they have called it that because of the smoke from the moonshiners fires?"

"Believe me," said Miller, "you wouldn't want to see any moonshiners' smoke. If you did, you'd know you were too close for your own good."

Moonshiners are gone from the canyon but it's not hard to see why they flourished here. The Smoke Hole is a remote place in hard, steep country, accessible only by boat. And some boats that go in don't come out in the same shape as when they started out.

That's something else we learned. The hard way.

The canoe trip with Miller's Rough Run Outfitters was organized by the American Rivers Conservation Council, a Washington outfit whose goal is to protect the nation's remaining freeflowing rivers from dam-builders and developers.

ARCC has a low-key educational approach. It aims to get people interested in rivers by showing them rivers. There are no long speeches or diatribe on an ARCC trip. "We let the river speak for itself," said Pat Munoz, who organized Sunday's adventure.

Sometimes rivers don't speak gently.

The South Branch of the Potomac was clear and smooth on Saturday, when most of the voyagers arrived. They pitched camp along the banks and watched fishermen stride off at dusk with stringers of bass and trout.

It rained hard that night. By morning, when they convened at the put-in, the Potomac wasn't clear anymore. It had risen muddy from the night-long rain and was flowing out of its banks.

"River's high," Miller conceded, "but we should get through. He gave a little stream-side lecture on paddling basics, then dumped 10 canoes overboard.

Violets and Virginia Bluebells bloomed along the grassy banks. Redwood trees blossomed purple in the craggy hillsides.

The line of red, yellow and green plastic canoes set off after Miller, who led. The first rapids were around the very first bend. You could hear the roar before you got there.

The boat went crashing through, bouncing along and shipping brown water from two-foot standing waves. All but one made it.

Ephrain Levin of Potomac and his 13-year-old son Dan had neglected to kneel down for the fast water. They bobbed twice in the thick chop and toppled over.

They were fished out quickly and the boat set right, but it was an inauspicious start to a 16-mile river journey on a cold, rainy day. Miller wasted no time voicing his displeasure.

"All right, now listen," he said. "This is not gong to do. I see you people coming through the rapids like you think you're going to a picnic.

"This river is running high and fast and it can be dangerous. It can kill you. If you're going to get down to the end safely you're going to have to paddle these boats hard. You're going to have to get aggressive.

"Some of you may have the idea that just because this is a guided trip everthing is safe and you can't get in trouble. Let me tell you that you can. e

"There's bad places in this river and you have to stay away from them, and the only way you do that is by paddling hard and staying alert."

Lecture done, Miller set off for th e next rapid and his chastened flock followed. And so it went the long day, from rapids to pools to churning rapids again.

Sixteen miles, is a long way on a river, and by lunchtime there were some worn-down paddlers in need of a break, which they got.

By midafternoon some folks were graning when they heard the inevitable roar of the next rapid. At last Miller pointed to one more ledge and offered the happy information that the final set of rapids was approaching.

That meant there was just enough time for one more disaster. The poor Levins, who had gamely held on in their wet clothes and who seemed to have the whole thing finally mastered, barreled over the ledge and saw ahead of them another canoe, side-on to the current. They paddled hard to avoid a crash and wound up flush against a tree on a midstream island.

The canoe curled over in a half-capsize. The current filled the bow and the current filled the stern, and then with a crunch the boat folded in half around the tree, its back broken by the force of the flow.

It took a crew of six better than a half hour to drag the mangled remains of the canoe off the tree, working in waist-deep white water. "I had no idea the river had that kind of power," said an awestruck onlooker.

It was a sad blow for Miller, who had donated his services for the ARCC trip and was now out a $400 canoe to boot. He took it in stride. "Same old story," he said. "One rock in the river, somebody's gonna hit it." "

ARCC always-seems to put together memorable canoe and raft trips. This was its first of the season, with others scheduled most weekends through mid-October.

The trips are generally donated by the outfitters, which means the $20 or $30 per-person fee for the most trips goes to ARCC coffers, so the organization can keep fighting to keep the rivers wild and free, which makes it a good deal.

For a trip schedule write to American Rivers Conservation Council, 323 Pennsyvlania Ave. SE, Washington 20023.