WHEN WAS THE LAST TIME you saw a new-born calf struggling to its feet for its first look at the world? Or reached under a hen to gather a still-warm egg for breakfast? Or sat in a wicker chair on a veranda and helped shell peas?

Maybe you never did. In any case, if you'd like to in the future, you'd better make your plans now. The family farm is giving way every year before technological agriculture and the romance for us city dwellers will be gone when the cows and chickens are all captive production units. Hurry, hurry, hurry if you want to see the farm as it used to be.

Up in Pennsylvania, the Department of Agriculture has compiled a directory of farmers who are willing to take in paying guests. The money you spend for such a vacation could make the difference between survival and disaster to some farm folk, who now also bear the additional burden of higher fuel costs.

There couldn't be a nicer way to help preserve a vanishing way of life. It's a reasonable and different sort of vacation. You'll be part of the family circle, a guest at their supper table, and they'll show you around -- even let you help. All the farms listed are inspected by the department and checked out for visitors.

Twenty-eight farms are listed in the directory, ranging from one that used to be the weekend retreat of playwright George S. Kaufman to one in Paradise, Pa., where the children of the house are fourth generation to live there. I chose Glen Run Valley View Farm in Atglen, Pa., because it was small -- 50 acres, reasonably close to Washington and was owned by a Mennonite family with whom we would take our meals.

Atglen is a village of 800 people in Chester County, southeastern Pennsylvania, and no road maps in our glove compartment showed it. My daughter and I finally found it in a very large road atlas and set off toward Rte. 1 -- once known as infamous Bloody Mary but now, since the advent of I-95, a has-been choked with local traffic.

Just beyond Oxford we struck off at Rte. 10 and at Chochranville to Rte. 41. It was right about there that we discovered that each of us was privately a bit apprehensive. It's a little frightening, even if you are paying, to be a house guest in a strange family. Leaving the credit card and the desk clerk behind is an adventure that you think twice about as you near zero hour. What would they be like? Would we, particularly in a Mennonite family, feel uncomfortably alien?

As we drove into the driveway of Glen Run Valley View Farm, Hanna Stoltzfur emerged from the front door and the sight of her made me feel better immediately. She was not quite five feet tall and her hair was caught in the traditional net cap which married Mennonite women wear. She was wrapped in a large apron and smiling as she waded through two excited dogs who formed the early warning system.

Glen Run, a smallish farmhouse which needed a coat of paint, could have come off the cover of an old Saturday Evening Post. Hanna Stolzfus led us through the kitchen, past a bear head mounted on the wall, through a living room full of potted plants and family tintypes of early Stolzfuses, up the stairs to a pleasent sunny bedroom decorated with cross-stitch mottos exalting friendship and love. On the dresser a bouquet of crocheted roses nodded in a souvenir vase from Niagara Falls. The single light was an unshaded bulb on the side of the wall and the hall bathroom was ours to share with the family. Everything was immaculate.

Meals are usually part of the package on a farm vacation and ours were included in the $20 each a day we paid. Our place were set at the dinning room table and heaping dishes of macaroni and egg salad, a mixture of beans, meat and potatoes, homemade rhubarb, homemade applesauce, bread and strawberry jam were handed round. Husband Harold was busy elesewhere, but their youngest son, Jeff, who had just graduated from high school, was filling in.

Over the banquet we learned that Glen Run's current crops are limited to corn and hay, though Hanna Stoltzfus also raises lettuce, peas and has a flower garden. Until recently some 35 head of cattle dwelt at Glen Run but they have been sold. Harold Stolzfus is semi-retired, but Jeff has plans to take over the farm and will go off to Penn State this fall to learn current agriculture methods.

The Mennonite way of life is based on farming, but outside cultural pressure has caused many of the younger generation to abandon the traditional lifestyle. One of the Stoltzfus' older sons drives a bread truck for a living. Another has left the Mennonite church. But Jeff will return to farm Glen Ridge, which eventually will be his. How he will reconcile new agricultural techniques with the basic Mennonite preference for simple implements instead of the engine to be seen. Some Mennonite farmers buy a tractor and leave it in the barn, while the horse continues to plow the field. The press of land developers has also disturbed the tranquility in the area.

In the kitchen beyond us sat an elderly man leaning over his heaping plate of food. Joe, a hired hand and county pensioner, lives with the Stolzfuses, feeding the chickens and doing odd jobs around the place in return for room and board and friendly companionship. Nobody passes Joe without a friendly word, a joke or a smile. The Bible teaches kindness to the less fortunate, and the Stolzfuses lives by the Bible.

Jeff had hurried through the meal in order to help hold the pig, which had to be castrated, but when we had finished our chocolate cake he was back to take us out to the hen house and the pig sty for a look round. Over the heads of the hens he told us that his second cousin, Suvilla, an Amish girl, would be spending the weekend with us.

The Amish, he told us, are a stricter branch of the Mennonites who believe that many of life's basic values are being lost in an increasingly mechanized world. He had barely showed us how to move over a setting hen to get the egg when a car drove up and Suvilla hopped out of the passenger seat. She was carrying a Bible with her name tooled on the cover and wore the traditional black dress fastened with pins and the special bonnet worn by unmarried Amish women.

Suvilla's black stockings and oxfords were at variance with a breezy, open manner that brought over even old Joe's wintery smile. We were all friends from the first introduction. On a farm vacation one moves very quickly into an easy relationship. A guests is an instant friend, so if you are not prepared for close companionship you should not plan a farm visit.

Hanna Stoltzfus and Suvilla tied on their aprons in business like fashion and we decided to steal an hour or so in nearby Bird in Hand. Jeff had suggested we might enjoy the Farmer's Market, but we found it rather disappointingly like any other neighborhood market. We did, however, buy some truly delicious Amis bread and, down the road a bit, some of the new and very popular sugar peas picked in the field while we waited. When we inevitably lost our way, we knocked on the door of an Amish family who allowed us to telephone outside in the small shack where Amish keep their telephones.

Hanna Stoltzfus is, as are many Pennsylvania Dutch women, an accomplished quilter. Wiping her hands on her apron, she took us upstairs to her bedroom where, on a gigantic quilting frame, one was in progress. From a closet she produced four completed ones, a waterfall of beautiful needlework spilling out into the bed. Baking, wuilting, her flowers and her church keep Hanna Stoltzfus very busy. She is obviously a happy woman.

Glen Run Valley View once extended well beyond its present confines. In 1930, Harold Stoltzfus' father sold part of it, retaining the farmhouse in which the family now lives, two barns and 50 acres. On Saturday at milking time, the Stoltzfuses suggested we walk down to inspect the part that was no longer theirs.

It was a lovely little road we walked. Beyond its fence the countryside seemed to have been painted by Andrew Wyeth. Great stretches of fields disappeared into patches of woods, punctuated here and there by silos. A possum waddled across the road in front of us and vanished under an unattended reaper. Chester County is lush with broad vistas.

A new little calf had been born only hours before and, as we watching, she struggled to her feet in the straw beside her mother while an array of kittens surveyed the event with pale yellow eyes. Five small boys, ranging from 12 years on down, had been left in charge while their parents went to a wedding and were busy offering bottles to the older calves who had difficulty nursing. The two smallest boys were hard to talk to, and later we found out why. They are taught only Pennsylvania Dutch until they go to school.

Supper was at 5:30 -- another mammoth banquet of beef, salad, baked beans, roast potatoes, peas from the garden, rubarb, three kinds of cake and two of pie. When the dishes were done, Hanna Stotlzfus proposed a visit to a Saturday night music fest in a nearby village.

We drove some 10 miles over narrow roads to a little outdoor amphitheater where eight fresh-faced young Mennonities set every toe to tapping with the rhythms of Mennonite religious music, which is as simple and catchy as the black spirituals of the South. A piano and three guitars backed up the mixed chorus, and seldom has "The Sweet Byb and Bye" been given such a beat. When they launched into "He Made a Believer Out of Me," even the matrons were tapping out the rhythms with their fingers.

Conversation in the car going home was an eye opener. "Lyndon Johnson?" murmured Suvilla. "Let's see. Wasn't he the one they put in after Nixon?" Far more interesting to her was neighborhood news -- what had happened to Art's eldest, where the young couple who had just been married would live, who had wished to be remembered to Hanna.

The next day was Sunday, and plans were made to pick up the widow woman in the trailer down the lane for church.

"It wonders me, ladies, have you ever had scrapple?" inquired Hanna Stoltzfus from her post at the stove.

We were always ladies.

Church was a two-hour participatory affair -- one hour of adult Sunday school considering how Jeremiah would have handled today's problems, and one hour of church. The little sunlit church was full, the matrons wearing their little net caps and flowered dresses made largely from the same pattern, the younger women wearing little lace covers for their hair, though the traditional dress is today going out of favor among the young. There was no altar, no organ, but a simple sharing of experiences and thoughts from the floor. And afterwards the kindest possible greetings for "Hanna's guests."

We had no Bibles, so Harold Stoltzfus lent us his, pretending he had left his glasses at home. When my daughter forgot the red cap she was wearing and left it under the pew, he drove us back over the roads, unlocking the church door to retrieve it. "And did you say a little prayer that we would find it?" he asked her, clapping it on her head, and there was a wink in his smile.

By the time Sunday dinner guests arrived from up Lancaster way, we had become such family friends that we ate in the kitchen with Joe and Suvilla and our hosts, occasionally lending a hand when things got busy.

Then it was all, as Hanna Stoltzfus is fond of saying, and time to turn the car back toward the city. Harold Stoltzfus followed us out to the driveway to shake our hands and wish us safe return.

"You'll be back, won't you?" he called, waving goodbye, and we promised we would.

Probably he says that to all the ladies.

Not all farms are Mennonite, and you may prefer a more elaborate and larger farm with your own bathroom. Some even offer riding and swimming pools; some, expecially in the mountains, offer boating and swimming. Some farmers have built special accommodations for visitors with air conditioning and TV. Some appear from the booklet to resemble ranches more than farms. The choice of farm is important and selection is difficult, since sometimes your must read between the lines of a farmer's thumbnail description of what he offers."

For a copy, write to Pennsylvania Department of Agriculture, Bureau of Rural Affairs, 2310 North Cameron St., Harrisonburg, Pa. 17110.