If a walker is indeed an individualist there is nowhere he can't go at dawn and not many places he can't go at noon. But just as it demeans life to live alongside a great river you can no longer swim in or drink from, to be crowded into safer areas and hours takes much of the gloss off walking - one sport you shouldn't have to reserve a time and a court for.

There is a time of life somewhere between the sullen fugues of adolescence and the retrenchments of middle age when human nature becomes so absolutely absorbing one wants to be in the city constantly, even at the height of summer.

Indeed, if "biology is chemistry with history," as somebody has said, then nature writing is biology with love.

Henry David Thoreau, who never earned much of a living or sustained a relationship with any woman that wasn't brotherly -- who lived mostly under his parents' roof . . . who advocated one day's work and six days "off" as the weekly round and was considered a bit of a fool in his hometown . . . is probably the American writer who tells us best how to live comfortably with our most constant companion, ourselves.

Black bears, though, are not fearsome. I encountered one on the road to my house in Vermont, alone at night. I picked up two stones just in case, but I wasn't afraid of him. I felt a hunter's exhilaration and a brotherly feeling.

Our loneliness makes us avid column readers these days.

If human nature eventually is going to take the place of nature everywhere, those of us who have been naturalists will have to transpose the faith in nature which is inherent in the profession to a faith in man-if necessary, man alone in the world.