IT IS NOT really surprising that there are now on the market at least three books that explain and commend to the American public the practice of walking. It has always been claimed that history was given a fresh start on these shores on the Fourth of July in 1776, and that America has now invented walking is only a sign that the boundless creativity of its genius is not yet dulled.

Such discoveries are always interesting to the outsider. When I first visited this country, for example, I naturally wore a waistcoat with my suits. My new American friends could hardly contain their mirth at so quaint a garment, the gentlemen withdrawing to cough behind their hands and the ladies to compose themselves behind the indoor plants. But I had only to wait for them to invent the thing for themselves - calling it, of course, a vest - and for two years it has been worn by every aging columnist or young Jaycee at a disco.

Although the American invention of walking is so recent, there has already been a decline in the number of strangers who exclaim, "You can't mean it - that you don't drive!", as if I had confessed to a defect of character, if not to some rare and terrible injury to my mind.

I have even been asked my advice on walking in recent weeks. "Should I take lessons or will one of the manuals do? . . . Does it matter which foot one starts with? . . . I supposed that in England you learn walking at school." At least one American has asked me: "If I stand on my tow legs, and lift one leg off the ground, to put it in front of the other, with none of the velocity of running, why won't I fall over?"

But glancing at the books on walking, and listening to those who have already been converted to the practice, I fear that it will be perverted, that walking will itself be deformed as a result of its invention here. The zeal that Americans bring to every activity of their leisure, the strenuousness with which they insist that exercise must do them good, will turn this most unforced form of locomotion into a new kind of harassment.

I know some middle-aged Americans who have already taken to walking to their work, and they are doing it as if they were back-packing on the Continental Divide. Their teeth are set into even the mildest of breezes, as if they are determined to be strengthened and purified. I once said that I had never seen a happy jogger; we may soon look in vain for a happy walker. The puritan will of the exerciser will have conquered.

Think of the words that used to be associated with walking. One strolled. One ambled. One perambulated. One sauntered. One meandered. One promenaded. The last thing one did, when one went for a walk, wa set out on a forced march. One went by footpaths and byways and, even on the sidewalks of city streets, changed one's pace and broke one's stride. The boardwalk, the promenade, the esplanade, the alameda: these are all words that tell what walking should be like.

The fact that walking might incidentally be of some physical benefit was expressed in phrases that were just as unzealous: one "took a stretch," or "took the air," or "took a constitutional." But already the American invention of walking suggests that the model will be unflinchingly military, and that what we see will be formations of pedestrians doing the quick step or the lock step.

The real pleasure, as it is also the value, of walking is that one takes one's exercise in a way that enables one to do something else at the same time - talk to a companion, maybe, or hum a ditty - so that the recreation of the body is accompained and enhanced by no less a refreshment of the spirit. This is one reason why doctors regard it as a natural form of exercise, and it is rather absurd to reinvent the practice now and make it unnatural. If the object is only the locomotion of one's limbs, one might as well take a turn around a prison yard.

Part of the pleasure and therefore the benefit of walking is to slow as well as to quicken: to stoop to a wild flower in one's path at dusk, wher "sleeps the crimson petal, and the white"; to slow to the pace of a stream along its bank; to pause to look at a copse of trees against the sky in winter, and be reminded that trees are lovely with no leaf. Especially in the country, one should have a stick, woman as well as man. The walker with a stick is always, with no break in his stride, and even none in the conversation, pointing out something in his path, a great root or the thinnest blade, or an insect scurrying about its livelihood.

Any walk should be, perhaps most of all, an exercise of the eyes. This is as true in the city as in the country. The true walker is also a born window shopper. Where is the exercise in that, the puritan will ask. Ah! that is one of the secrets of walking, as one does many things and not just one.

The walker has the time to glance and, even on the most familiar of streets, there is always something to notice. No building is the same when one walks home in the evening, the usn slanting from the west, as it was when one walks to work in the morning, with the sun climbing in the east. But then buildings also change with the different people in front of them: they are in this as alive to the play on the sidwalks as the backdrop in a theater.

One never knows what one will not see for the first time, at a pace and a mood that allow such discovery. I once gazed down at my feet on a stretch of Connecticut Avenue that I must have covered ten thousand times. I suddenly saw what I had not noticed before. Each of the slabs of which the sidewalk is made has on it the mark of the WPA and the date when it was laid. I was walking on the New Deal, and the feeling was no different from walking on the Roman Wall, for I was walking on history.

Of course there are hazards for the walker in the American city. When I lived for a time as a pedestrian in Houston, and then in Los Angeles, I began to develop a neurosis about being a biped. I used to set out to go to the supermarket on Westheimer, which is one of the main thoroughfares of Houston. I had first to beat down the vegetation that sprang from the sidewalk, like undergrowth in the tropics, and push aside the branches of strong saplings in my way. Only by persistence and daring did I reach an island in the middle of the road.

There I was stuck, it seemed forever. Five lanes of cars sped by in front of me, five lanes behind had closed the way back. How I had got to the island in the first place I never understood; it can obly have been by closing my mind and my eyes to the dangers. But that I might perish on the island, just wither away, was by no menas the worst of my anguish. What I could not bear was the fact that, as the cars approached from both directions, their drivers looked at me and shuddered, as if I were some alien life, and rolled up their windows as they passed.

Even in the cities in the East, which were not made for the automobile, there is now a new danger to the walker. On what is supposed to be his sidewalk, he is quite likely to be knocked down by a jogger. It is the jogger who expects the walker to leap out of the way, siince it is difficult and even dangerous for him to break his stride. There ought to be special lanes for joggers, in the middle of the roads between the cars.

But the real danger to the walker in America will still be those who make a mission of walking. Walking is the most social form of exercise. One cannot talk to a friend if one is panting, or chasing a ball, or doing 16 lengths of an Olympic-size pool. But what really tells one of the character of walking is that it is still a social activity even when one goes for a walk by oneself.

I have a phrase that I use naturally - I did not notice it until a friend pointed it out - "I took myself for a walk this afternoon." All that it means is there. The walker is still able to be company to himself. Thinking, pondering, reflecting, humming, reciting, remembering, noticing. Walking is an act of communion and, if Americans now invent it as a form of drill, it will lose all its purpose and charm.