As I approached Judd, my knees literally shaking, I began to question my own good sense. Judd was a 1,000-pound mule, and I was about to spend the next five hours on his back descending on a 10-mile trail to the bottom of the Grand Canyon.

"Remember," the wrangler chuckled as he helped hoist me over the saddle, "the only reason Judd is going this morning is because you want to go."Then he handed me a metal whip and said to use it.

There are three ways to get to the bottom of the Grand Canyon - hiking, rafting or riding a mule. Hiking seemed to me too strenuous, especially the climb back up. Rafting down the Colorado River seemed too dangerous.

But mule riding, that seemed to be the way to go. Let the sure-footed crossbreed do the work while I enjoyed the scenery. My wife, Wendy, agreed, and we decided to take the overnight trip in early October.

But here I was sitting on the back of a mule, it was raining and so cold I was shivering, and all I could think was how nuts I must have been when I made the reservation. How could I have thought this would be fun? Then Judd headed out of the stone corral onto the Bright Angel Trail, and I realized that my fears were ridiculous.

To simply stand at the edge of the Grand Canyon and stare out at the vast expanse of carved earth is breathtaking. But to sit on a mule more than 5 feet tall, riding along the very edge of a sheer cliff with the Colorado River raging below is thrilling. Four million people visit the South Rim Village at the Canyon every year. Only 1 percent are smart enough to take the mule trip down.

The adventure begins by checking in the day before the trek at the Blue Angel Lodge, a popular hotel in the village. Mule riders are asked to sign a release form and are given their gear - a yellow rain slicker, an empty 5-pound plastic ice bag for carrying clothing and a leather water bottle. If you do not already own a cowboy-type hat, they will sell you one. Then you have to weigh in. Fortunately, I did not exceed the 200-pound limit. You cannot ride if you do.

The next morning, we arrived at the stone corral at 7 a.m. lugging our ice bags stuffed with one change of clothes and, of course, a hair dryer. I was surprised by the diversity of the crowd. Middle-aged men and women, some less than svelte, were suited up in their yellow slickers ready for the trip. There were about 40 people at the corral, but only half were going to the bottom. The rest had signed on for a day trip.

We were greeted by Ron Clayton, the manager of the mule tours for Fred Harvey Inc., which started the service in 1876. Clayton, eating a Baby Ruth candy bar for breakfast, described what to expect and outlined the rules of the trail. There would be two groups of 10 riders going to the bottom, all that was allowed on any given day.

And the key to a safe trip was not allowing the mule ahead of you to get more than 5 feet away, which inevitably happens. Mules run to catch up, and that can be frightening as they walk along trails often not much wider than their shoulders.

To keep up, Clayton advised, prod your mule forward with the small metal whip. "The key to the ball game is a tight pack," he said. "If you don't keep up, you'll become what we call around here a hiker."

There are 14 wranglers working for Clayton. The day I rode a married couple from Louisana, Mitch and Phyllis Devilla, led the two groups. Phyllis was my guide, a former psychiatric nurse who said that she found her retirement dream job at the Grand Canyon.

Slowly the mules left the corral and stepped onto the 4-foot-wide trail. The first turn was sharp, and mules take turns like a truck, going straight toward the edge then turning at what feels like the last minute.

Phyllis stopped the group after the first switchback. The mules were positioned so that their heads faced off the cliff. Everyone smiled nervously. "If you're scared and you want off, let me know now," Phyllis said. "You'll get a complete refund. This is your last chance."

No one took her up on the offer, and we were off. The ride down was slow and winding. As I fell into the rocking rhythm of the mule, the walls of the canyon rose around me. It was a magnificent sight, but because I was on a mule I could not read the park service signs discussing the geology. If I had known this before departure, I would have purchased the trail guides available at the village gift shops and read them beforehand.

I also learned that riding a mule is more strenuous that I imagined. My knees ached.

The weather in the canyon was much warmer than on the rim. In three hours we arrived at Indian Gardens, a small camp where we stepped off our mules and ate a box lunch.

By noon we were back in the saddle. We rode through creeks, ducked our heads beneath rock cliffs and then came out onto the Colorado River. This, to me, was the high point of the ride. The trail is literally carved into rock, on the right a stone wall, on the left a cliff, and below that the river.

"We're approaching what we call the Grand Canyon sand dunes," Phyllis said as we neared the end of the river trial. Then she pointed to me and said that my mule liked to lie down in the sand. She told me to hit him if he tried to.

By this time I was very comfortable on Judd. I felt we had an understanding - he did not act cranky, and I did not have to whack him. But the idea of this animal dropping out from under me on a precipice did not sit too well. So I gave him a swat.

Well Judd did not like that too much, so he shot out of line and galloped through the sand. For an instant all I heard was laughter. But mules do not run too long, and soon he ambled back into line. From there, it was a quick trip through a 60-foot tunnel, over a 440-foot suspension bridge and onto our destination - the Phantom Ranch.

The ranch is a series of stone and wood cabins built along with a mess hall in 1922. They are equipped with bunk beds, cold-water sinks, flush toilets, electricity, alarm clocks and are very clean and comfortable. The cabins are reserved for mule trippers, but a dormitory built in the 1970s, and camp grounds are available to hikers and rafters, too. There is an outhouse with hot showers that is only available to the residents of the ranch.

At the bottom, it was 84 degrees, and a cool wind blew. It was about 2 p.m. when we arrived, and we had a couple of hours left to explore the canyon floor before sunset. When the sun is down it is too dark to wander, and bats come out and swoop all around. They do not bother anyone, though.

Dinner, which is included in the mule-tour package, was served at sunset. There was an unlimited supply of steak, corn, salad and potatoes for the mule trippers, who ate around one big table. Afterward the mess hall became a beer hall, and the hikers, rafters and mule riders sat around drinking beer and chatting. By 10 p.m., we were sleeping.

The next day, after a filling breakfast of eggs, pancakes and bacon (also included in the package), I was back on Judd at 7 and ready for the ascent. We took a shorter trail out, called Kaibab Trail, which stretched only 7.5 miles to the top. It is steeper, and the view is more stunning than the trail down.

The hikers we passed looked enviously at Judd. My knees ached again, but the sight of the sweaty hikers made me realize my logic had been sound after all.

By noon we were back on top of the canyon, once again surrounded by a crowd of tourists who were satisfied to sit on the edge and stare out in awe.