Sometimes the trip seemed like a lark, an idyllic getaway Huck Finn might have dreamed up. At other times it seemed like the brainchild of a knucklehead. Huck, after all, had a raft. I walked.

For two weeks in May, I walked along the Potomac River on the towpath of the C&O Canal. It was a journey of 185 miles from a Gulf station in Cumberland, Md., at the foot of the Allegheny Mountains to a chocolate-banana ice cream cone at Hillary's Gourmet Ice Cream store in Georgetown.

That cone showed the extent to which isolation can undermine one's judgment. I traveled alone, carrying my belongings on my back, sleeping out nights by the river, trudging toward home by day, favoring my feet, stopping to talk when there was someone to talk to and to watch when there was something to see.

A hundred years ago, the C&O Canal was a busy waterway linking the coal fields, flour mills and lumber yards of Western Maryland with the tidewater port of Georgetown. Aware of the oratory in 1828 in which the canal was compared to the pyramids of Egypt and the Colossus at Rhodes, a curmudgeon might disparage it today as an overgrown ditch of stagnant water and fat, happy mosquitoes that lap up insect repellent like salad dressing.

Yet the towpath along which mules plodded for 94 years still offers a sort of passage. More than 5 1/2 million people visited the C&O Canal National Historical Park last year, and many found what the late William O. Douglas, to whom the park is dedicated, found: "a refuge, a place of retreat, a long stretch of quiet."

For the hiker who takes on the entire length, the towpath is a way through the world, dividing a dead canal and a live river, contrasting the stink of sewage with the scent of wild rose, teaching the feet the forgotten hardships of a mile, joining a small city full of rail cars and pale faces to a metropolis of air quality indexes and Perrier jogging shorts.

The towpath has its own rhythms and moods. It changes with the hour, the day, the season. Along some sections on weekday mornings there is scarcely anyone but a bird watcher, standing stock still, with binoculars trained on a pileated woodpecker or a prothonotary warbler, and wearing a satchel on a belt that inevitably contains Roger Tory Peterson's guidebook. I did not meet one birder who, learning I possessed the guide published by the National Audubon Society, failed to gaze at me with a sad and patronizing expression.

"You must get the Peterson," I was told.

In the evening, fishermen appeared toting poles down to the river and boxes of bait--worms, minnows, even canned corn and Velveeta cheese. At other times, especially weekends, the towpath teems with mushroom hunters, horseback riders, bicyclists, river rats, canoeists and kayakers. I saw a woman walking a ferret, a kindly girl with a club foot, a man who eats robins.

Some people linger in the memory long after even a brief encounter. Near Harpers Ferry where the towpath intersects with the Appalachian Trail, I met Harry F. Thompson, a 51-year-old Winnebago Indian, making his way north, hoping to get to Maine in time to pick potatoes in September.

Near milepost 151, Mike Thompson of Flintstone, Md., walked out of the woods wearing a gold chain in a mat of chest hair and a T-shirt that fit like a second skin. He had violently blue eyes and the sort of build that made you want to get on his good side. We talked snakes. Cutting trees along the towpath on a CETA crew, he contended with copperheads all the time. One day, running a chain saw, he happened to glance down and saw a rattlesnake cocked to strike his leg. He reacted instantly: brought the chain saw down like a machete and juiced the rattler's head. He had the skin worked into a hatband.

On weekends, the towpath crawls with boy scouts whom some people consider a species of pest. (Until the National Park Service planted 100-pound concrete mile posts, scouts frequently uprooted the mile markers of their troop numbers.) I passed troops from Bethesda and Hagerstown, and sat in on the Sunday service at milepost 175 of Troop 603 from Delaware, Scoutmaster Ed Kuenzle at the pulpit. Perhaps the feeling of history that pervades the path inspired him, for he urged the nine hellions in his charge to "remember our mothers and grandmothers and our great-grandparents." The troop then sang "Kumbyah," Kuenzle performing the song in sign language which helped him remember the words.

All along the path, there are suspensions of time in which it is hard to tell the present from the past.

"When I took my bike trip it was like traveling in time," said Larry Woods describing his bike trip down the towpath to Georgetown from his home in Shepherdstown, W.Va., 72 miles up river. "I could hear the bugles and the voices that cried 'Lock ready, Lock ready.' When I got to Great Falls, a canal boat was locking through, and people were dressed up in costumes. I thought I was in the 19th century even though there were hundreds of tourists with Kodaks and Bermuda shorts."

For a hiker, this phenomenon is partially a function of taking two weeks to cover a distance a car can span in three hours--of living outside and gauging time by the sun. What Douglas called a certain "understanding" of nature comes to people traveling at such a pace. To be frank, it is hard to say if the understanding is the same along the stretch where the towpath is paralleled by Interstate Rte. 70 and the pastoral soundtrack consists of belching tractor-trailers. During this bleak segment I could not help feeling as if my car had broken down somewhere on the median and I was in the middle of a 185-mile walk to a gas station.

Elsewhere, the towpath is steeped in the loud quiet of the woods. At evening the croaking frogs sounded like buzzers at high school basketball games; at dawn the birds were deafening. Even the trains booming through the valley at all hours of the night are of a piece with the place, for it was the new age of the railroad that eclipsed the era of the canal.

Passing cemeteries of canal workers, caves and quarries, a bend in the Potomac where whiskey once spilled into the river and caught fire, the towpath leads past limestone kilns and old cement plants to the legends of headless men. It runs past the ford where Lee's Confederate Army crossed the rain-swollen Potomac after the carnage of Antietam.

History and stories, and the names of people lie at every turn. Zip, Punt, Pickles, Billyo, Trough Mouth, Satchel Face, Chow-Wow, Snoggles and Socrates were names that once were shouted out along the canal. The people I wished still lived were the Stumph sisters--saloon-keeper Gene Stumph's quintet of red-haired daughters who were said to be such pretty sights to the boatmens' eyes that they became landmarks of the upper canal.

Mostly, my companions were the canal and the river, and after a while I was preoccupied by the river. It would wander in and out of view. A breeze might bring its dank metallic smell. On cold mornings its surface smoked. Mist coiled about the sycamores and maples and wreathed the long traveling boughs of elms. Winds blew white-capped waves against the current. The wake of a passing boat spread a widening furrow that slopped against a muddy bank, filling the tracks of raccoons.

The Potomac went through gorges, branched around islands, received other rivers. In the mountains it danced and jabbered in its bed. It tore itself into rapids, raving and boiling, and then grew sedate and sluggish in stretches of slackwater. It sledded massively over dams, and stormed through falls in thundering cataracts. It came to a sort of restfulness where I left it, reposing with placid grandeur in the upper reaches of seatide.

The river is more than 500 million years old, yet it seemed newborn each morning. Indeed, beside the ruins of the canal, the boarded-up lock houses, the people who'd come and gone, it seemed to flow outside time completely.