THERE IS a secret path from Silver Spring to Georgetown that winds among some of Our Town's prettier parklands and boskier backyards.

Eventually the right-of-way of the B&O Railroad's abandoned Washington spur line may become a public pathway, but for now the rusty and rotting old railroad track is the Trail of the Outlaw Hiker.

"Outlaw" because the line, which until last year carried the coal that powers Georgetown, has not yet been legally abandoned. The B&O has installed no fences or "keep out" signs, but would rather people didn't walk on the track because they might a) trip on the ties or b) topple from a trestle and c) sue, as even burglars are doing these days. Your correspondent, who recently hiked the whole 11 miles, can testify that stumbling and tumbling are real possibilities.

But if you take it easy and watch your step, the B&O spur offers an unusual look at some serene -- as well as some seamy -- sections of Silver Spring, upper Rock Creek Park, Bethesda, Little Falls Branch Park, Dalecarlia Reservoir, the tail end of the Potomac Palisades, and the C&O Canal. Although the right-of-way is never more than a block or so from "civilization," there are stretches of a mile or more in which the track itself is virtually the only sign of man. If you don't count Budweiser cans.

Official approval of abandonment of service on the line is expected, but a number of conservation and recreation groups are asking the Interstate Commerce Commission to use its powers to preserve the right-of-way for public use. A number of homeowners, worried about an influx of strangers, are trying to buy the railroad strip adjacent to their properties or to have the land reserved for neighborhood parks.

The railroad property is coveted by Montgomery County and such organizations as the Washington Area Bicyclist Association and the Capital Hiking Club as a recreational and commuter hike/bike path. Many of the folks whose backyards abut the right-of-way are understandably suspicious of the various proposals, especially when planners start mumbling about shuttling buses along the 60-foot strip, which in some places runs on an embankment that towers above adjacent homes. A more likely outcome is a modest path similar to the W&OD Regional Park in Northern Virginia.

One who has hiked the spur, however, may find himself in sympathy with an elderly Bethesda apartment dweller who has turned part of the railroad land behind his building into a beautifully landscaped sit-a-bit spot. "I kinda like this rusty old railroad the way it is," he says.

The whole route can be hiked in about six hours, including lunch and rest breaks plus brief exploratory side trips, but this probably would be considered something of an ordeal by any but a hardened hiker. The grade is level only on the average: The ties are irregularly spaced and unevenly ballasted, so that it isn't possible to establish a standard stride or a steady pace. Paths parallel parts of the track, but for the most part the footing is picky, picky, picky. Light, stout and well-mannered hiking boots with firm ankle support are a must. Companions are a comfort.

A logical way to break up the trip is to start in the middle of the spur, which falls quite conveniently at (under) Wisconsin Avenue and Elm Street in Bethesda, and head east toward Silver Spring or south toward Georgetown.

Although the Silver Spring leg has several scenic points, including Columbia Country Club, Chevy Chase Lake and Rock Creek Park, it is not the choicer route. The most convenient exit point is in the industrial outback where the tracks intersect Lyttonsville Place off Brookville Drive near the Walter Reed Hospital Annex, and it's not all that convenient. Another option is to drop off into Rock Creek Park and head back toward Washington.

The Bethesda-Georgetown leg is considerably more sylvan, once the hiker has cleared the heavily trashed downtown section, where everything including at least three kitchen sinks has been dumped down the embankment. If you're not packing a lunch, better belly up to the salad bar at the Roy Rogers, because the next convenient place to put on the feedbag will be the Little Tavern on M Street in Georgetown.

Less than a mile from Bethesda the railway enters Little Falls Branch Park, and thereafter there's shade almost all the way. The park doesn't have much wide, but it has lots of long, and surprising solitude. By and by it blends into the Dalecarlia Reservoir reservation, the changeover being signaled first by the peeping of the wood ducks, and then by the Dalecarlia Tunnel, a mighty and musty edifice of brick built in 1910.

Sit quietly for a while almost anywhere along this stretch and you may see several other species of ducks and, early or late in the day, Canada geese. Pileated woodpeckers, perhaps a nesting pair, keep up a nearly constant hammering, but the big gaudy birds are shyer and harder to spot than most of their suburban brethren.

Adjoining Dalecarlia is the highly fenced Defense Mapping Agency, where they also do other things, none of which they will talk about. The track runs right through the DMA compound, which has been there a long time but still has that air of improvisation and impermanence that pervades most military installations.

The home leg into Georgetown is marked by a stripped Porsche that has been rolled over the bluff, and a battered safe lying beside the tracks. Hikers under nine feet tall should wander somewhat to the right of the railway, the better to see the view along the Potomac near Chain Bridge.

Just beyond the Canal Road/Arizona Avenue trestle the track curves to parallel the C&O towpath, busy with its grim runners and hurtling bicyclists. Human voices wake us, we're in town.