In the beginning the boy was 5, and his executive input on our canoe trips was pretty much limited to "Don't bump rocks" and "Let's eat" and "Hey Dad, stop snoring!"

Lacking size and skills to haul and paddle, Mark was a passenger, an observer. His young eye was sharp and, not yet having learned how to overlook things, he showed me unsuspected sights as we drifted and camped along the Rappahannock, Potomac, Shenandoah, Cacapon, Monocacy and half a dozen other half-wild rivers. He pointed them out left and right while standing in the bow like some Hudson's Bay Co. captain commanding his voyageur.

A frog eye-deep in frog-green watercress. Tiny wood ducklings hiding underwater while their mother watched from an overhanging limb, shifting nervously from one foot to the other. Otters and ospreys where neither was supposed to be, and other unlikely announcements. One morning as we paddled the upper Rappahannock he sang out about a two-headed cow. From then on I was wary of challenging his identifications, because just as I finished explaining about perspective and overlapping images, there she was, swaying in agony and exhaustion at the edge of a wood, half-delivered of a calf that had died after its left foreleg had gone wrong.

The other lesson I learned that sweltering summer day was the futility of trying to kid the kid about what was what. While we stood around feeling sorry for the huge helpless animal, the friend who was canoeing with us went off to find the farmer. He wasn't around, but somebody promised to pass the word, and we prepared to push on.

"Someone will come and take care of her," I told the boy. But the calf was starting to bloat, and the cow's eyes were rolling and she was down on her knees, groaning softly.

Mark's eyes started to roll, too, not believing we could actually abandon her, and so of course we couldn't. At length, in a muddy muckle of blood, toil, fears and sweat, we freed the beast of her burden and ourselves of the shame of denying the oneness of all creatures great and small.

You cannot step into the same stream twice, as the man said, and each of our trips over the following decade has been very different, even those that have covered familiar stretches of favorite rivers. Floods undermine banks and change the channels, unknowing boaters pry away the rocks of ancient Indian fish weirs, tree roots split boulders and undo their own footholds, a cabin looms above a backwater we had come to regard as reserved for the otters and us.

But the pace of these changes is glacial compared to what's been going on inboard. After progressing from passenger to paddler the boy began to demand his turn in the stern, where he could tyrannize me for a change; mutiny was avoided by enlarging the fleet so he could have his own boat. Where once he followed my lead through rapids and shallows he now goes his own way; and often I find myself awash or aground as Mark sails merrily on. Too many items of food and gear turned up missing too many times, so he has taken over the planning and packing, and supervises the shopping.

While he's been growing up I've been growing older, of course, and while that's a whole lot better than either of the alternatives, it is attended by a certain melancholy. In the metaphor of time and the river the point where boyhood shades toward manhood is not when you can paddle your own canoe but when you can pick it up and carry it, and this has been that summer. Mark staggers but he does not fall.

That every father endures this ambivalence of feeling pride and loss together makes it no less new for each of us. But few can have had the privilege, as I did one night a few weeks ago, of having the occasion marked by symbolic combat and celebratory fireworks.

The Battle of Chipmunk Corner, as we have come to call this fight of passage, was fought between our small camp and a great crowd of rowdies on the opposite bank of a river I had better not name. It has long been the custom of campers here to put on rival fireworks displays as darkness comes on, the effect being magnified by reflections from the hundred yards of river between and echoes from a vast sheer cliff that turns the river and creates the bend my daughters named Chipmunk Corner because of the squeaky little rascals that raid camp kitchens. Fountains, aerial flares and rockets are set off turn and turn about, with each camp applauding particularly good efforts by the other.

This night, however, the display was followed by a barrage of bottle rockets aimed at us from the other shore. Several of them exploded among our tents, and our cautionary shouts were answered by jeers. The snickering pyrotechies fired again and again, serene in the belief that we had no more shot in our locker. But we were just back from vacation at North Myrtle Beach, S.C., and still had several gross of bottle rockets in our watertight cans.

We hit the beach and began to retaliate. After a few ranging shots Mark began to fire for effect, and the effect was dramatic. First he laid down rapid suppressing fire that so rattled the aggressors they never again managed to land a round within our perimeter. Coolly he shifted to pinpoint counter-battery fire, routing the rowdies from their prepared positions and so harrying them that they seldom got off more than a shot or two before being forced to cut and run.

As senior officer present I should have been setting an example for my troop, but early on in the affair it became apparent why as an army draftee I was assigned to the infantry rather than the artillery. So many of my shots were shorts and overs that I gave up and began just opening packets and setting fuses for Mark. His was a well-earned battlefield promotion, and I felt privileged to follow the orders of a fellow I once had had the honor to command. With someone serving his guns our new brevet captain was free to range up and down the bank, keeping the enemy in range while presenting them with an ever-changing target.

The Battle of Chipmunk Corner went on for fully half an hour, ending in a victory so complete that several squads of our assailants literally folded their tents and drove away.

Dumb? Yes. Dangerous? Yes. Bad example? Perhaps; time will tell whether he was growing up or I was growing down. But I am proud to have been present on the field.