Think of this. You are standing at the edge of a very high cliff. Beneath your toes, the cliff face drops away for a thousand feet. Space, hungry and empty and dizzying, opens out before you for miles and miles. The wind rolls over this smooth and spraddled valley and hits the cliffs, then swoops up over their top like surf over reefs. Wind suck, they call it, and sometimes it's strong enough to snap up over the cliff edge and flip your glider onto its fragile spine. But it will not do that today; it's flowing steadily, warm and gentle. Above you, the sunpolished sky glistens. Away to the west, soft blue ridglines rise from gray haze.

Wings sprout from your back. Not Icarean dreams of feathers and wax, but sturdy spreads of aircraft aluminum and sail Dacron. Forty pounds and twenty feet of wings: the hang glider. Now the wind washes steadily over its surface, giving lift. To your left, an orange windsock fills. You look to your wingtips, where launch assistants are holding on to wires. They both nod, signaling equal pressure. Your nose man nods, too. It's time.

"Launching!" you scream, and their hands spring away. You sprint five steps to the cliff edge and leap out, plunging away from your stomach and from every screaming self-preservation instinct as well. You fear drowns in adrenalin, the electric liquor. This is it: the Ultimate Rush, for down there the springing ground wants your soul.

But, dropping, you gain speed. Your wing comes alive, develops lift. The control bar jumps in your hands and you pull back, just a little, stop falling, level out, listen to the whine of wind in the wires and stare into the eyes of a hawk.

It is, unquestionably, magic. The weird freedom unstraps your mind. Circuits ablaze, you hear laughter, wild and ecstatic, and realize it's yours. The wings, great aluminum bones, are extensions of your arms. You dive, and neurons rip fire like machine guns. Then you just fly, riding updrafts and cliff surge, circling, diving climbing again and again until, hours later, you drop down over a plowed field, flare the wing softly, and settle onto your own two feet. The springy earth feels strange, for your eyes are still full of the sky, dazed with ectasy, changed.

This is hang gliding, brought to you by an ingenious NASA engineer named Francis Rogallo. Rogallo began toying with designs first seen in the magical sketchbook of Leonardo da Vinci. He improved upon models built by Otto Lilienthal and the Wright brothers, and perfected what men had sought for centuries: a heavier-than-air, fixed-wing glider that could be carried, launched and landed solely by pilot power. His early wings were basement-workshop constructs of bamboo, polyethylene and strapping tape. Nerve-wrenching, but they flew. That was in the '60s, and by 1972 mass marketing had spread swarms of gliders over the world. Perhaps predictably, under-trained pilots were diving into the stony earth with alarming frequency. Responsible heads in many countries formed governing bodies, the American version of which is the United States Hang Gliding Association. Ruling with peer pressure and manufacturer concordance, the USHGA has succeeded in dramatically reducing the numbers of deaths and injuries, so that gliding is now statistically no more dangerous than downhill skiing, SCUBA diving or rock-climbing. That has led to its being taken up by a growing body of enthusiasts, which in turn has produced better gliders, certified instructors, pilot-rating programs and competitions.

Who hang glides? Anyone who believes, as Hicks said in Dog Soldiers, that a little adrenalin is good for the blood. A recent beginner's class at Sport Flight, Inc., of Gaithersburg included business executives, secretaries, students, a preppie and two reporters. There are some physical prerequisites, of course. You need to be strong enough to lift a 40-pound glider, and agile enough to run downhill with it. An extra dash of courage helps, because it's a little scary at first, this idea of sailing off terra firma and wafting through the air. But skiing and surfing and climbing are just as scary. After all, the hairy-scary part is what it's all about. We want it that way. Perhaps we need it that way.

But the road to thrills should be paved with common sense. Anyone who wishes to fly will want the best instruction available, and that means a qualified school; there are two in the area. After ground school, students take to training hills, usually on the weekend following ground school. Accompanied by an instructor, they travel in small classes to a hill that's right for the wind on that particular day.

And then comes flying. You stand atop the training hill, pick up the glider, level the wings, raise the nose. Watching your instructor at the bottom of the hill, you wait for the wind to be just right. When it is, you run like hell downhill and in seconds the wing lifts you right off the ground. You're flying! Seconds later you thump down again, sometimes in an unceremonious sprawl, almost before you realized what was happening. But after half a dozen flights you grow accustomed to the weird sensations and actually begin to pilot your craft. You make turns, gain and lose altitude, pick your landing spots. The hours disappear too quickly after that, and soon you are diving home over hard concrete. But your brain is still sailing around in the sky.

If you are good, and fly every weekend, in six months or so you'll be ready for that Ultimate Rush, the cliff launch. You must be certified by a United States Hang Gliding Association examiner before you can take the first gut-wrenching leap. But when you are ready, there are places like High Rock, near Camp David in Maryland, and Massnutten, in the Blue Ridge. From their heights you can launch and stay up for hours, climbing thousands of feet into the clouds, performing delicate aerobatics, navigating cross-country to those distant blue ridgelines. You can whirl with eagles and hawks and dive into fiery sunsets. You are literally, as free as the wind. And that is good for the blood.