By RAY WADDLE

GRAND CANYON, ARIZONA -- At the South Rim of the Grand Canyon, I woke up one recent morning to find snow on the ground and panic in my heart.

This was the day my wife and I were to climb onto mules and climb into the canyon -- the Hummer of all mule rides, a one-day-round-trip so popular that we had to book it months ahead. But now it was 7:30 a.m., 25 degrees and the trails were an Arizona mishmash of icy mud. Not exactly what I had in mind.

With dread we left the cabin and trudged to the nearby corral at Bright Angel Lodge, the popular South Rim accommodation.

A few others, mostly couples, were sheepishly gathering. Fateful scheduling had brought us together into this slush of anxiety -- worries about ice on narrow trails, fear of leading a 1,000-pound mule along steep cliffs, doubts about stamina and now sanity too.

Everyone hid their panic. Our exuberant plan still held, if just barely: We city folks were there to grab some gusto and test ourselves in rugged conditions under the western sky in ways unavailable in the suburbs back home. Nevertheless I cocked a doubtful eye at the turbulent sky.

Then the mules arrived, a caravan of 10, the inscrutable stars of the show, moving slowly up the hill with a trio of cowboy-hatted wranglers. All of them, humans and mules, looked calm, business-like. It was reassuring to see. Just another work day for them, weather or not.

And so it is: The Grand Canyon mules have been working the trails of this grandest of national parks from the early days more than a century ago. First they carried equipment into the vast gorges for exploration purposes. Soon they were carrying people down on recreational odysseys.

Mules -- the offspring of a male donkey and female horse -- seem built for Grand Canyon. They carry more weight than horses. They are less temperamental. They are famously sure-footed. One reason: Their eyes are slightly set back, allowing them to watch all four of their feet as they walk.

The literature here says there has almost never been an accident involving mules in the Grand Canyon -- and never has a human death been associated with passenger mules into the canyon.

I kept these soothing statistics in mind when the tough-talking mule company operator gathered us for the preliminary shakedown talk.

“Safety, then fun” summarized his theme. He was 50-something, mustached and suffered no fools. We are here to create lifelong memories, he said, but safety is top priority.

Follow your guides, he said. (We would have two guides today, one leading, one at the rear.)

We were handed leather whips, “motivators” to keep the mules on pace. Do not be afraid to use them, he commanded. It will not hurt them. They are trained to take it. Use them.

Safety first, he repeated. If you get hurt down there, it will cost $2,000-plus to helicopter you out, and theyre not paying.

He offered us one last graceful out: Anyone unwilling to do the mule ride could leave now with full refund, no dishonor, no questions asked. The time was now or never.

Whether out of defiance or some secret negotiation with ones very soul, no one stepped forward to bail out.

He squinted at the cold windy sky.

“Today will either be one of the most memorable and thrilling days of your lives, or it will be the most miserable day of your life. I havent decided which.”

He directed us to the muddy corral, where our two guides were waiting. We were lined up and matched with mules, according to size. My wifes mount was Betty. I got Johnson, a bluish silver male with a bit of attitude.

“Make sure he knows youre in charge,” one guide told me.

Each of us was helped onto a mule. On the saddle horn we wrapped our newest proud possession -- a leather water pouch, filled to bursting. It was issued as a souvenir.

Suddenly we were off, clopping in an orderly line down the trail that begins at Bright Angel Lodge. Gazers along the rim turned to stare -- some combination of admiration for the animals and disbelief at the folly of humanity. It seemed a reasonable attitude.

Any musings on the human condition quickly gave way to something more pressing -- the sheer need to hold on for dear life. You tense your legs in the stirrups, grasp the saddle horn and hold the reins too. You focus on your mule walking speed, the mules ahead and behind, the next turn, the many hairpin turns and switchbacks that will mark the daytime adventure. You dont even worry about any slush on the trail: It might be a hassle to hikers, but it is a non-issue to mules. Their hoofs bit into the muck and plowed forward with humorless efficiency.

Two minutes into the ride, the lead guide was already shouting at us to stay in line, use the whip, do not fall behind. He had all our names on a sheet and didnt hesitate to use them.

“Ray, you going to make it?” he said, eying me warily.

“Got no choice,” was all I could think to say.

Now the trail passed along the first sharp cliff of the day, maybe 200 feet down. I am not very good with heights. It was a source of late-night worry before the trip. But now it didnt matter. I was too busy to worry -- busy learning the muley ways of Johnson, finding the right walking pace, blending in and not being conspicuous to the watchful guide.

Barely 10 minutes into it, an unexpected mood settled in. You relax on your mule, who is doing the real work anyway. The trail is suddenly free of ice and mud. In fact, the sun is coming out. And you are heading into one of the greatest wonders of the world. There is nothing to feel but joy.

And it was getting warmer by the minute. At Grand Canyon, temperatures rise as you descend. The walls of cliff and rock turn a delicate orange in the morning sun. The vast canyon was opening before us, with little glimpses of the great river at the bottom of it all, the Colorado, which carved and gashed the vast sandstone steadily over millions of years to create the canyon.

Soon enough we were at the three-mile stop, where we tied up the mules, got off, stretched, replenished our water bags and lined up at the restrooms. The terrain had changed dramatically -- from high severe rock, to sloping vegetation and stone and trees and stream. Our confidence had grown. At the break there was a bit of swagger to our walk. Or maybe that was just leg stiffness. Appetites had grown too. We were glad we packed trail mix to devour. It was just 9:30 a.m.

The stop was brief. The two guides reestablished an earnest mood, telling us to get on and keep a tight line. This is the dual reality of the canyon mule ride -- the need to be attentive to silent animal and snarling guide while at the same moment gasping at the fast-changing scenery as we dropped altitude.

We were now reaching semi-arid conditions -- cacti surrounded us. There was even a good stretch of flat country as we approached our destination, Plateau Point, a shelf of rock that is situated halfway down to the bottom of the canyon. It faces the cliffs of the North Rim and overlooks the green-blue Colorado, 1,300 feet down.

The morning was gone. It was lunchtime at Plateau Point -- the turnback point on our seven-hour round trip. The sky was a brilliant implausible blue. The early blustery weather was a faraway memory. It was 65 degrees. The guides brought out box lunches for everyone. Summer sausage, soft cheese button, granola bar, corn chips and apple never tasted so good.

Suddenly we had a visitor ...