Kilimanjaro. As we ascended, the terrain transformed, the vistas shifted, the climate cooled from tropical to frigid

AT the base camp, parties of onlookers encourage each other in anticipation of high adventure. Tomorrow we begin our trek to the top of Mt. Kilimanjaro - rising a snow-capped 19,340 feet above sea level. I wondered if the climbers from other countries had been grouped as casually as the four other Americans I had linked up with a few hours earlier. We ranged in age from 23 to 46 - two businessmen, a violinist, a student, and a doctor from an Indian reservation. When I left Santa Fe, N.M., the others were at airports in North Dakota, California, New Jersey, and Nevada.

Our Kenyan guide, John Ochieng, had met us in Nairobi and driven us across the Tanzanian border to the base camp, temporarily abandoning us to the park bureaucrats while he negotiated the price for the climb, the provisions, and the services of the porters, cooks, and guides who would accompany us.

In his continued absence the next morning, we learned that two Austrian students and seven porters would join us. As we passed the time rearranging the backpack necessities for daytime travel, we speculated that our needs were less of an issue than converting United States dollars at the black-market rate of 2 times the official exchange.

At last Mr. Ochieng reappeared, wearing a wide grin on his weathered face. This clearly indicated his satisfaction with the bargaining. Briskly he escorted us past the entrance of the park to the trail, which would lead to three campsites located a day's climb apart. We would ascend to the summit at dawn on the fourth day.

The first 24 hours began in a heavy stand of rosewood trees rising 50 to 60 feet. Rays of sunlight filtered through, glancing off drops of moisture on the dense lower foliage. We picked our way onto patches of red clay over moss-covered rocks, decomposing trees, and large exposed roots. At 3 degrees south of the equator in the dry month of August, we oozed along for 5 hours at a steady incline of about 15 degrees, steaming sweat at every step. We began at 6,000 feet, and would reach a plateau 3,000 feet higher by day's end. Vegetation thinned increasingly as we entered the lower moorlands in the last hour. We eventually collapsed at a clearing dominated by tall grass and giant senecio trees.

The following morning, our campsite seemed to float on a shelf over the rain forest, and the clouds below remained intact during the morning's climb. As mid-afternoon fatigue set in, the sun finally broke through to cheer us on to our bivouac at Horambo camp. During the cloudless night, with sleep elusive in the oxygen-thinned air, temperatures dipped below freezing.

With us at Horambo was a group of older Germans who had spent the previous day in camp adjusting to the altitude, as the less-conditioned usually do. We left to climb another 3,000 feet in our six-mile hike to the Kibo Hut. The terrain bore witness that Kilimanjaro is a volcano, inactive since the Ice Age. Enormous boulders replaced the sparse foliage of the previous day. Underfoot was a dust as fine as hourglass sand that had been produced as melting snow eroded the lava. The newest feature of the landscape was our trail itself. Ever since a German, Hans Meyer, published an account of the first climb of Kilimanjaro, in 1900, the trail has been trodden down by thousands of adventurers.

As afternoon approached we saw climbers descending from the summit, after reaching it that morning. Long past our arrival at the day's destination, they were returning to Horambo for an overnight and then on down to the base camp the following day. A Japanese climber remarked that during the last day's climb his feet seemed to be encased in cement boots.

Tired and chilled, we arrived at our third campsite, Kibo Hut, and found it nothing more than a scaled-down way station. Food was in short supply. Moreover, to minimize oxygen deprivation, we were to begin the ascent in the dark, reaching the summit at dawn.

We arose at midnight to temperatures just below freezing and to a moonless sky. Armed with flashlights in the dark, we faced a disorienting grade of more than 20 degrees. An unnatural pace of two steps for every breath worked well, even when my steps shortened and breathing accelerated.

I cast my flashlight on my wristwatch for some sense of distance. At 4:30 a.m., I figured we must have covered about three-fourths of the ascent. As I returned the beam to the trail, the flashlight dimmed and went out. In the dark, staying on the trail became even more challenging. With no alternative light or spare batteries, our guide was of little help. Stumbling onto a mammoth rock shelf, I dismissed him and rested.

Even protected from the wind, I was numbed by the chill and by the thought that I was some sort of sacrificial victim on that rock slab. Yet, having survived my share of misadventures in the rugged terrain around Santa Fe, I had gone to Nepal and the base camp, where only a well-conditioned few set out to scale Mt. Everest. And that experience had led to this climb.

``Next the Andes,'' I thought, suddenly encouraged when I saw the first light of dawn.

As my eyes became adjusted to the dim light, I set out again. Soon I linked up with a party of Germans who were struggling, sometimes on all fours, to penetrate the increasingly thick, granulated lava.

As the ascent grew steeper I programmed myself to rest after each dozen steps, sip some water, and readjust my backpack. Robot that I became, I wondered if my boots felt more like lead than the Japanese climber's had like cement.

Finally, a white, wooden cross appeared in the distance. The end of the climb. In a frantic burst of energy I scrambled over the last field of volcanic boulders to the almost level crater edge.

My exhilaration at reaching the summit was short-lived. The Reusch Crater below was without a jot of color - a dun-colored chasm. It was as massive as I imagined the bleak surface of the moon to be. My American companions and I spent an anticlimactic hour taking photos and scouting out the unusual perspectives we had climbed to see. With gravity as our tailwind, we would soon descend swiftly into denser air, foot-loose and carefree.

Yet, before we began our descent together from the heights each of us had truly reached alone, for a brief moment we shared the feelings of Hemingway's hero in ``The Snows of Kilimanjaro,'' who took an African safari to ``work the fat off his soul.'' If you go

A number of airlines serve Nairobi, with connections through London or New York. Nairobi abounds with travel agencies that have international contacts. Guided climbs of Mount Kilimanjaro, as well as Mount Kenya, are not recommended during the rainy seasons, March through June and November through December.