All kinds of things pass for pure sport. To me, pure sport is sailing in a centerboard boat.

I was reminded of this simple truth last week when a long string of desultory days ended, as such strings generally do, with the arrival of an invigorating cold front.

The Washington summer haze was swept off by a wicked northwest wind that put whitecaps on the Potomac. George Stevens and Bill Fox and I went sailing in a Flying Scot that sparkling day.

It made for an interesting crew. Stevens is a positive fanatic about the Scot and about small-boat sailing, having campaigned the boat we were in in national racing championships. I'm something of a weekend warrior. Fox, a convert from powerboats, never had sailed a real sailboat before in his life.

Stevens put Fox at the helm, which served to keep things interesting.

We set off into the teeth of a 15-to 20-knot breeze that was booming down through the concrete stanchions of the Woodrow Wilson Bridge.

While Fox clung to the varnished wooden tiller in the stern, Stevens and I perched high on the windward rail, balancing the boat and peering down at the water boiling along the rail on the lee side.

"We are really flying," said Stevens. A sailboat will not go directly into the wind. The wind was coming from Wilson Bridge and we wanted to get there. In order to do that, we had to set a course as close to the wind direction as we could, which had us sailing diagonally up the river.

When we ran out of water on one side, Fox would turn the boat sharply into and through the wind. The sails would flop over to the other side and we would sail diagonally the other way.

This is called tacking.

The most satisfying feat in sailing is to tack perfectly, going from the highest point of sail on the other without loss of boat speed.

But there are at least a million things that can go wrong when sails are flailing from one side of the boat to the other and sailers are clambering across the rope-strewn cockpit to get to the windward side.

Generally, something goes wrong. The challange of sailing is to comprehend everthing that's going on in chaotic situations like this, to recognize that there's a problem, identify it and correct it. In a centerboard boat, you usually have about one-tenth of a second to do all that. If you foul up, you could go for a swim.

During our first two tacks on the wind-whipped Potomac, my unfamiliarity with the Scot caused me to mess up.

The first time through, Fox barked out the orders he had just learned. "Prepare to come about," he said, and Stevens and I said "Ready."

"Tiller to the sails . . ."

Fox jammed the tiller over and the boat swung into the wind. Stevens and I climbed down off the windward rail, ducked to avoid the boom as it swung across with the mainsail and stepped across the centerboard trunk.

Somewhere in the middle I felt a line snare my foot. It was the jib sheet. Quickly, I had to map out options.

We'd need the jib sheet to trim the sails on the upcoming tack. I could stop now and free it, but the mainsail was just about to fill and my weight was needed on the other side of the boat to keep from capsizing.

On the other hand, if I got on the hight side and the line was still wrapped around my foot, we'd have no control over the forward sail and it could flap and flutter itself to shreds.

Better a torn sail than a capsize, I reasoned, and jumped for the windward rail. I reached down and deftly unsnarled the line and sheeted the jib in. No harm done.

I congratulated myself on being the brightest, most agile person i'd met in the last four seconds.

Next tack, something similiar happened, only this time I wound up sitting on the cleat Stevens needed to sheet down the jib. Everyone in the boat could feel that something was wrong, but only Stevens knew what it was, and of course there was no time to express it.

He could say, "Would you please get up so I can secure this jib sheet in the cleat you're sitting on?" By which time, we'd all be taking a bath.

Instead, it had to be this curious mixture of instinct and reason -- something's wrong; what is it? how do I fix it? -- all in a millisecond.

I figured it out, got up and we were off and running.

Every sport probably has this element of snap judgement translated into instant action. That's probably what sport is.

For example, the writer John McPhee once did an exhaustive study of Bill Bradley, the basketball player, in which Bradley described in minute detail just why and how his hook shot worked.

Bradley said there were five distinctive parts to every hook and every time he missed he could explain what part of the sequence had broken down.

But most people go up for a shot in basketball or out for a pass in football and either it's there or it isn't. In sailing, every success or failure has specific, easily traceable causes. A good maneuver is a perfect union of mental prowess and physical skill.

In a keel boat, the same laws exist, but a keel offers protection. All that weight below the waterline makes it almost impossible to capsize, so it's possible to goof around for a lifetime in a keelboat and never really pay the price.

Stevens figures anyone who doesn't know how to sail a centerboard boat doesn't really know how to sail.

Of course, even the experts are imperfect.

We made the bridge in fine form, sailed daringly through the stanchions and took one final tack before rounding up for the gentle run home with the wind behind us.

The sails were trimmed and the boat was heeling handsomely when a big puff roared down from Hains Point, smacked us broadside and tore the jib in two, surprising everyone, including Stevens.