The weekend is over, and we drive down the country road from the cottage to the pier, passing out our last supply of waves. We wave at people walking and wave at people riding. We wave at people we know and wave at people who are strangers.

The island wave is by now a summer habit. It took me time to acquire this salute, but now it feels a natural part of life in Maine. Like year-rounders, we pass back and forth the visual assurance that anyone on our island belongs here, is accepted.

When we arrive at the pier, the boat is already crowded with the end-of-summer exodus. Island emigrants help each other stack cat carriers and lift bags onto the back of the boat. Crossing the water, everyone is patient with each other's dogs and children.

But by the time the three of us have transferred from the ferry to our private car and reached the turnpike, my wave has begun to atrophy. Before we cross the Maine border, my hand has entirely lost its training. As the hundred miles go by, even the toll-takers have turned from smiles to surliness. The jawlines of drivers in other cars seem to set as the city skyline rises.

To ease my reentry into workaday life, I decide to walk the last mile home. I am left at a familiar, safe city corner and, yes, almost immediately, my accent changes. I begin to "speak" in the city's body language: neutral and wary.

Suddenly conscious of my own adjustments, I notice how few eyes meet on this mile. Women do not look at men. Old people do not look at teen- agers. Men do not smile at each other. People don't wave to strangers on these streets. They measure them.

A quarter of a mile from home, inevitably, I pass two young men who give their own obnoxious verbal greeting to every woman who crosses their stoop. By the time I reach my own door, I go over the threshold as if entering a haven.

This small pilgrimage from rural community to city is not unique. But today I am peculiarly aware of how my own trip seems to mimic American life.

Our whole country has moved from rural communities to cities, from towns where contact was reassuring to cities where contact may be threatening. In 1900, 60 percent of us lived in the country; in 1980, 74 percent of us lived in the city. We have exchanged being known in small communities for being anonymous in huge populations.

It is this easy public space that seems to shrink as the population increases. Millions of us have exchanged a street life in which we acknowledged each other for a street life in which we deliberately ignore each other.

I am not glorifying rural life. I know that in small communities people have to struggle to maintain their privacy, their individuality. The same society that supports people can confine them. The same people who help each other some days annoy each other on other days.

But in the city, people have to struggle to make a community. We have to recreate a world in which we are known. We fight against anonymity at the grocer's, the dry-cleaner's, the newsstand, the coffee shop--and are often thwarted by the supermarket, the discount pharmacy, the fast-food counter.

The more anonymous we are in public, the more we forget our small towns at work and home, among family and friends. But our communities are private ones. Indoor ones.

I'm not sure why it's so hard to maintain some sense of community in the city streets. Perhaps it is just arithmetic. At a certain point, numbers make strangers.

But I suspect that it is also because we urban people think of ourselves as transients in our communities. Even the third-generation city people travel light. We don't sink our roots in neighborhoods as deeply as our grandparents did. We don't claim the street turf.

Pascal said, "We do not worry about being respected in the towns through which we pass. But if we are going to remain in one for a certain time, we do worry. How long does this time have to be?"

I don't suppose any visitor cares if he is known in a strange city. But many of us live our whole lives as if we were just passing through.

And if we are all tourists, where are the natives to teach us how to wave?