Chauffeured limousines hardly raise an eyebrow at Philadelphia's Reading Terminal Market, but to see the chauffeur doing the shopping would be another matter. The venerable ladies and gentlemen who command those limousines do the marketing themselves, poking at the mallard ducks, sniffing the cheeses. They wouldn't miss the fun. More than supermarketing, which is usually a matter of choosing between yellow and orange cereal boxes or cello-wrapped flats of identical grass-green pears, shopping at marketplaces is participatory shopping.

City markets are, of course, no longer a necessity.City governments indulgently put up with them, knowing they occupy valuable land that could become an important parking garage. Shoppers travel past several supermarkets early Saturday morning to get the day's crop of elderberries before it disappears. Even the farmers might make more money by trading the cherry orchard space for soybeans. But markets fill another, less obvious necessity, that of a gathering place, a community center, the crochet hook of the neighborhood. And along the way they serve as the last stands for crops with short seasons and small supply: intensely perfumed white peaches, fresh tarragon, wild rabbits. A supermarket with 50 branches can't waste its time with a few baskets of black raspberries. In a society pressing always toward sameness, the market is a preserve of distinctiveness.

Originally, markets were not built to be profitable for the city, but to bring low-priced food to urban dwellers by eliminating middlemen, and to protect buyers from unscrupulous purveyors of tainted food. They were a small-scale FDA and trade commission.

The centers of activity, markets were usually adjacent to city hall and attracted a great variety of services, from barbers to marriage brokers. You could buy a pot to cook your chicken in, or sell a pillow you stuffed with its feathers.

By the end of the 19th century, Baltimore could boast over 5,000 market stalls; in the next 20 years the United States doubled its number of markets, and Washington had five.

They came supermarkets and suburbs.

As the central business districts of American cities declined, markets became anachronisms. Suburban growth ate up the farm land, and supermarkets developed as efficient machines for moving food in, people through and food out. Chain stores were cheaper - not to mention faster and cleaner. The farmer's spiel was replaced by the advertisement on the package, the farm wife's timely recipes and budget hints by the magazines sold at the supermarket checkout counter.

Eastern Market's historically-registered structure by 1958 housed five stalls, where it had once sheltered 85 stalls and a restaurant.

Not all movement was in one direction, though, in 1930, for instance, Bethesda started a farmer's cooperative market in a tent to help farmers recover from a drought. Growing affluence and suspicion of processed foods joined with nostalgia to create a demand for real food. Once people had bought a hand-thrown pot, they needed something appropriate to put in it, hand-grown, hand-cooked, hand-sold.

In Washington, the city had already sold some of its markets, and was looking into new uses for the Eastern Market site by the mid '60's. But something halted the dosposal; as General Services recently put it, "It is a political decision, not a business decision, to keep the markets."

It has to do, some people think, with brown eggs.

Brown eggs, if you ask experts on the subject, are identical to white eggs except for the color. A lot of shoppers believe differently. A farmer at the Eastern Market repeats, "Everybody wants brown eggs." Handlettered signs on market stalls announce supplies of brown eggs. Supermarkets don't sell them.

Whatever the reason, markets are back. Eastern Market is up to 40 stalls and a waiting list. One purveyor at Baltimore's Lexington Market sells over a million raw clams and oysters a year. Alexandrians veture out before 8 a.m. to get to their city market before it closes, and two stands at Bethesda's Farm Women's Cooperative require customers to take numbers, their lines are so long. On the site of an old gas station at 18th and Columbia Road, a small, outdoor market has sprung up on its own. And the about-to-be-revived Georgetown Market on M Street has been considered worth a major investment by its organizer as well as by government. On Capital Hill, it is said that people buy houses there because of the Eastern Market. Along with street vendors, markets are making a comeback nationwide. If you wander through the markets, it is obvious that the reasons have little to do with money or efficiency, the kinds of necessities that first encouraged the market system.

Self-service isn't for everybody. Some people like someone to tell them about the food, to pick it out for them, to explain why they should buy and how. "It's cut fresh last evening," says the farmer of her watercress, or, "I had to get these cherries off the tree before the birds ate them, but they'll ripen up by tomorrow."

People like to taste the cheese before they buy, or have their chickens split and pounded flat rather than quartered by machine. They know Mrs. Farmer will save them a pound of her country sausage, or make them a special batch with extra sage.

At a market, they can find nearly extinct specialties - home-smoked chicken, pork pudding - which can only be made is small batches. They can get small-crop or highly-perishable products such as shelled fresh peas, sassafras or fresh eels. They can choose from six kinds of greens or eight varieties of apples. Supermarkets can't be bothered, ans without such an outlet, nobody might grow or catch such specialties.

If shoppers save money by shopping in markets. It is usually because markets sell some budget-stretching foods such as pig tails or fish heads, not because the foods are cheaper than the same items at supermarkets. One Saturday eggs were 80 cents at the Florida Avenue Market, 85 cents at Eastern and 90 at the Georgetown Market on Grace Street. Supermarket shopping would have turned up better buys.

but market foods are usually fresher - or at least younger. Even when purveyors at the Florida Avenue Market buy all their chickens at the nearby wholesale market, they are sold that day rather than trucked around to supermarkets around the beltway. At their best, markets sell foods picked or plucked that day. But even if not, they don't have the storage space that allows the long-term keeping the supermarkets can manage. And markets can adjust their supplies day to day, reacting sensitively to demand rather than being locked into a large scale system. The shopper may keep those fresh foods in the refrigerator a week, or freeze them, but still prefers to buy them first-day fresh.

While certainly shoppers greet their neighbors in supermarkets, markets are synonymous with social exchange. Stallkeepers offer a taste of deviled ham to a customer, then turn to the next to offer some. The two customers start talking about deviled ham. And when they encounter one another next week, they asked how each other liked it. Thus, markets become meeting places. Said purveyor Mitch Berliner at the Bethesda market, "This morning there were at least three or four hugs in front of here," and it was only noon. The mode may vary, but one expects to interact with the people at the market, maybe goes there for that reason.

And one chooses a market as much for its personality as for the foods it sells or for its proximity.Ripe peaches are sold at any of the markets, and the nature of the exchange differs more than the fruit does.

Eastern Market is the oldest of the current markets, and serves as a neighborhood center to the extent that the community devotes a special annual festival day to it. Cutting across social lines, it sells fatback and pheasants, ground beef at 69 cents a pound and caviar. Inside stalls range from homegrown foods to mass produced bakery items. It is the variety, the choice, and the generally high quality that people say they like. One stop shopping for fish, rye bread, flowers, artichokes. Outside are the farm lines; though they are available to rent, like the interior stalls, throughout the week, and cost only 20 cents a day, farmers rarely come except Friday and Saturday. They bring their chickens, their day lilies, their blackberries. Churches have bake sales, and young women peddle their own whole grain breads. Prices seem irrelevant; people don't seem to ask.

The second city-owned operating market is on the Maine Avenue waterfront. Open-air, and bustling until late at night, it is devoted almost entirely to seafood, and serves as much as a tourist attraction as a food facility. Sixteen boats, each paying $3 a day rent, sell crabs and Chesapeake Bay fish that look fresher for being sold on the water, but may or may not be. Shopkeepers actually live on the boats a week or two at a time, and since the city closed down the stands for sanitary reasons, they now sell from the boats themselves rather than on the dock; thus, they are subject only to federal laws. The only on-shore sales are in the new Morgan's seafoof building. The scene is festive, colorful and, if one has to wait in line to have the fish fileted or the oysters shucked, cheerfully inefficient.

Rock music blares at the Florida Avenue Market.Behind cinderblock walls and wire fencing, cabbage vie with figs, hot peppers with candy bars. Stall after identical stall is piled with greens or potatoes from the adjacent wholesale market, though farm foods are woven in, with the occasional homemade pepper relish. Some purveyors are tough and uncommunicative, others breezily familiar. But here price is the thing, specials and bargains the call. There is some of the unexpected - cows' feet black walnuts - and the beautiful - okra arranged in concentric circles, red-and-green hot pepper plants - but, unlike the other markets, here there is no shame in selling limp greens, cloudy eyed fish, or decaying fruit; the seller is distant from his supply as well as from his buyer. Still, there is the air of a disco, the smell of fried chicken, the call of friends across the heads.

Not quite a market, the privately owned Georgetown Market on Grace Street has only four purveyors, and a lot of their business involves deliveries rather than on-the-spot shopping. Glamorous produce - fresh tarragon and kiwis - are at Hudson Brothers, which serves some of the finest restaurants in town. The meat market's signs are in French. Burrows' chickens are decked with parsley. Mr. Muir sells not only cheeses, but thick yellow cream and butter. A few farm stands outside on Saturday sell fresh poultry, flowers, home-baked breads and cookies, and produce from their farms in season, from California out of season. If there is any doubt about markets catering to luxury trade, Georgetown dispels it. Shoppers are as likely to wawr tennis dresses as French jeans, and prices are hardly mentioned.

Until the new Georgetown Market reopens on M Street, the only other market in the District is the few stands at 18th Street and Columbia Road, one of them selling organically grown produce from a Maryland farm, the others a hodgepodge of imported pineapples, lettuce and such.

The incovenience of the Alexandria city market is proof of the intensity of shoppers' desire for markets. Just about everything is sold out by 8 a.m. - the home-baked banana nut bread, the oysters, the aprons and pot holders, the country ham, the spring water, the hot soup. Cyclists are returning home, straining to see over their armloads of flowers.

Bethesda's Farm Women's Cooperative goes on later in day, but there is not much choice past noon. Everything in the market is locally grown, according to the market's regulations, or homemade. Shoppers, often with children in tow, stock up on oxtails and potato salad, fragile leaf lettuce and crisp green apples. Only in the suburban markets are home-cooked foods allowed, and here barbecue smells mingle with egg rolls and Jamaican meat patties, for the farm women have been recently admitting urban stallkeepers. This has led to a revival of the Wednesday market, as nearby office workers wander in for an on-the-hoof lunch. Still, Wednesday is only half as busy as Saturday.

Which shows that markets, no longer a necessity, need a certain magic formula of timing, location, and stock - enough varied goods to make the trip worthwhile for customers, enough customers to make the trip worthwhile for farmers. And because shopping at a market does not preclude a trip to the supermarket for tissues and milk and cereal, markets require days, usually Saturdays, leisurely enough to draw the casually spending sightseers as well as the serious shoppers. As long as there are Saturdays, it seems, there will be markets.