By Marcus Ferrar

DOLAM KENCHO, Bhutan, Dec 5 (Reuter) - It is the last evening of a 10-day trek through the snowy peaks of Bhutan's Himalayas, and herdsmen are rounding up yaks for the night in a mountain glade at 3,650 metres (12,500 feet) with strange, melodic cries.

From down below come the calls of men driving another caravan of packhorses and mules up the valley to join us for the night. It is a magical moment, and for a tourist on a trekking holiday in this tiny Buddhist kingdom tucked between India and China, there are many such moments.

Bhutan, which only began to appear on the tourist track about 10 years ago, counts as one of the tougher Himalayan countries for trekking.

Once outside the settlements in the valleys, there are no roads, no hotels, no signs, only rudimentary maps and the occasional primitive habitation. All supplies and provisions must be brought along on packhorses, mules or yaks. Travel is done on foot, for 160 km (100 miles) or more.

THE UNRULY, IMPETUOUS YAK

The yaks who have been carrying tents, baggage, food and cooking stoves for the two tourists and the guide, assistant and cook accompanying them are unruly beasts of burden.

They are immensely strong and amazingly nimble, but only half-tamed and equipped with a dangerous pair of horns to express their impetuous wills. If you meet a caravan of yaks coming down a steep mountain path, don't wait to ask who has the right of way stand well clear as they thunder past.

When a caravan reaches its destination, the yaks must be lassoed by the horns before they can be approached for unloading and must be tied up at night or they will walk home.

And then there is the altitude. A "medium" trek takes you to 4,850 metres (nearly 16,000 feet). The gradual ascent helps acclimatisation but few trekkers escape the resulting headaches and giddiness entirely. Over 4,000 metres (13,000 feet), each step upwards seems to take twice as much effort as expected.

During the day it can be warm but at nights you huddle in sleeping bags on the hard ground in little tents in temperatures often well below freezing.

Many tourists encountered on the way, typically from the United States or Europe, appear slightly traumatised by the rigours. Many cannot take it and give up after a few days.

But most take a deep breath, brace themselves, and plunge onward. The hardy are rewarded with beautiful views of morning mists rising to reveal sunlit, snowy peaks over 7,000 metres (23,000 feet) high most of which have remain unconquered since authorities rarely grant climbing permits.

BUDDHISM IS EVERYWHERE

The people are equally enchanting. In an ancient fortified monastery at Lingshi, 4,300 metres (14,000 feet) high, lives a lone Buddhist monk. In his prayer room, he shows you his deities and a collection of ancient helmets, swords and shields captured from invading Tibetans over 100 years ago.

In return for a small donation, he gives you cool holy water scented with sandalwood from a decorative metal can. Nearby peasants and herdsmen bring him food and yak butter to make holy candles. He spends the day praying, meditating and preparing peacefully for death and reincarnation.

Bhutan's society is deeply imbued with Tibetan Buddhism. The land is dotted with huge monasteries, many of them 300 or 400 years old. Most were fortresses in the past, and nowadays serve as centres of civil administration.

Villagers gather in the central courtyards waiting for legal cases to be heard or rhythmically turning the prayer wheels which they believe spread Buddha's word throughout the world. Inside little has changed over the centuries.

Religion is one reason why Bhutan gets few visitors. At the end of the 1980s, the clergy curbed tourist visits to the monasteries, which are the country's main cultural attraction.

They have opened up again, but tourist numbers are restricted, partly by the expensive package visits tourists are required to join.

Ten years ago, accessibility was a problem. Now, Royal Bhutan Airlines flies tourist from Delhi, Bangkok and Calcutta, landing on an airstrip deep in a valley.

Once outside the little airport building, built in traditional Bhutanese style, life slows to a gentle walking pace. Cows wander languidly across the few roads, and dogs sleep in the midday sun. Tourists are met with smiles and easy-going hospitality.

SLOWLY OPENING TO THE OUTSIDE WORLD

It is a country opening to the outside world only slowly, anxious to protect the conservative values of its mountain folk.

But Bhutan is alive with foreign-aid projects. The British have put up a hospital, the Swiss launched cheese- and jam-making projects, the Danes built a major waterway project.

And Indians are everywhere, working on aid projects, in shops, on construction gangs and in military garrisons along Bhutan's frontier with China.

Even remote mountain areas are slowly moving into the modern age. Back in Lingshi, the schoolmaster opened a primary school here last year. He now has 73 pupils and holds exams out in the meadows among grazing yaks because his schoolroom is too small.

He lives in a small, simple house with his wife and young child, sipping tea mixed with yak butter on furniture he has made himself. He has made his own primitive device for duplicating exam papers. He proudly shows the completed exams, almost all with correct answers written in English.

Up in the nearby pastures of Barshong, a pair of educated young Bhutanese students are hiking from homestead to homestead with heavy backpacks.

They leave a few basic medicines at each home and give advice on healthcare and nutrition. A few months tramping the mountains is part of their training as paramedics. For some mountain people, it is their first exposure to modern medical care.