THE LAUNCH ORCA cuts its engine and wallows gently under the soaring cliffs of Boreray, one of three massive rock stacks off St Kilda. Crag after bird-infested crag rears above us, into the low cloud, streaked with guano and traceried by white ranks of nesting gannets, while thousands of others wheel overhead. At 60,000 nesting pairs, the stacks host the largest gannetry in the world.
It is as if we have sailed into one of Gustave Dor's illustrations for the Rime of the Ancient Mariner. Another world; yet it was only as recently as 1930 that Hirta, the main island of St Kilda, ceased to be a place of continuous human habitation, as its lingering handful of population gave up the struggle against a hostile environment and boarded a boat for the mainland.
Today the St Kilda archipelago, some 45 miles west of the Uists, remains a byword for remoteness, filed away in our imaginations with the likes of Tristan da Cuhna, St Helena or even the Romans' Ultima Thule.
Now with a transient population of conservationists, ornithologists and missile monitoring personnel, its status as Scotland's first UNESCO World Heritage Site, awarded in 1987, was extended last month to cover its human heritage: the roofless stone cottages, drystane dykes and prehistoric-looking storage shelters that bear witness to many centuries of human resilience.
The extension of the World Heritage Site status to include cultural as well as natural significance is very important, says Neil Mitchell, the ranger for the National Trust for Scotland, which manages St Kilda in partnership with Scottish Natural Heritage and the Ministry of Defence. "St Kilda is hugely important as a seabird colony, but there is also the whole cultural aspect - the community that lived here and their dependence on the seabirds for a unique way of life."
Mitchell is speaking in his office in the former factor's house on the main island of Hirta, where the laird's representative would stay when he arrived each summer to collect rent. Beyond the white plastered house stretches the "main street", with its gaunt line of stone cottages, all roofless but for six which have been refurbished to house visiting National Trust work parties, and one containing a museum. The morning's heavy cloud is lifting and sunlight is sweeping across the pasture that softens the great natural amphitheatre that opens out to Village Bay, now cropped by Soay sheep imported from the neighbouring island.
"It is such an amazing history here," Mitchell continues. "We've got definite evidence of permanent habitation going back to about 2,000 years ago, but it's highly likely that people were visiting the island, possibly just during the summer months, as far back as 5,000 years ago. You can see the distinctive shape of St Kilda from the Uists, and on a good day it would have been relatively easy to get over here."
We'd visited some notable relics of earlier Hebridean societies on our way down to Harris, taking in the famous standing stones of Calanais (or Callanish) and the broch of Carloway, both in Lewis. At Calanais, the striated stones rose amid the buttercups. Despite Historic Scotland's imprecations, visitors - perhaps inevitably - love to touch them, listen to them, run their fingers over their timeless, lichened bulk, feeling for ancient vibes, one supposes.
Did the raisers of these stones, some 2,900 years before Christ, have the means to visit the lonely crags which beckoned on the western horizon? When the first tourist steamer arrived off Hirta in 1838, the locals ran to the manse to report a ship on fire. By the early 1900s, the islands had become such an established tourist draw that its mailbag for that year carried nearly 800 postcards, with short-term benefits for the island economy. St Kilda continues to attract visitors; and, since February, a fast boat out of Harris, the Orca, has provided a daily excursion trip to the archipelago, weather permitting. It usually takes just two and a half hours to get there, compared with anything up to 14 hours from the mainland.
Even so, things looked less than propitious as we growled into the Atlantic from Leverburgh on a depressingly overcast July morning. The launch's 700 horsepower engine was slamming us through lumpy seas, its owner, Angus MacDonald, describing conditions as moderate to poor: "I wouldn't come out in anything worse than that."
Not wanting to donate our generous breakfasts to the fishes, like most of the dozen daytrippers we stayed outside the cabin and braved the elements. The fins of a basking shark slid past, and a squadron of shearwaters flitted low through the troughs, wingtips clipping the water with easy grace.
One-third of the way across, MacDonald announced that it was make or break time: the word from St Kilda was that it was just as overcast there, with no guarantee of the weather lifting. He'd turn back if we wanted. The consensus, however, was to plough on, and a couple of hours later the cliffs of Hirta loomed indistinctly out of the mist and we were into Village Bay.
The initial prospect is of the ultra-utilitarian cluster of 1960s-built accommodation for the former Defence Establishment Research Agency presence, now privatised as QinetiQ, which monitors missiles fired from Benbecula. These glorified portacabins, along with the neighbouring generating station, don't always sit well with those expecting a pristine antique village-scape. "Military-inspired vandalism", a recent writer to The Scotsman called it.
Mitchell appreciates the problem, but explains that QinetiQ enables the NTS to remain on Hirta. "They provide us with all our electricity for work parties and visitor facilities. Without the QinetiQ presence, St Kilda would be a different place, but they work very closely with us and within the environmental guidelines the NTS requests to maintain the World Heritage site. Those buildings were constructed in the 1960s, and are certainly due to be looked at, and I'm sure we'll see changes for the better in that respect."
Eyesores apart, one small disappointment was to learn that the Puff Inn, Hirta's famous howff, regarded as the most remote pub in Europe, appears to be officially closed to visitors these days, catering only for QinetiQ and approved NTS personnel, owing to public liability legislation.
Beyond the accommodation blocks, the deserted village offers poignant testimony to a vanished community - the main street, its cottages open to the shifting sky, was where that famous photograph of the "St Kilda parliament" was taken in 1927, although the uncompromising-looking islanders in their beards and bunnets appear to gaze from an earlier century. The museum contains further pictures showing island life as it was: hardy women spinning tweed; the men clambering about hair-raisingly precipitous crags, hunting the gannets and fulmars which were their staple diet, particularly in winter.
In the empty school house a faded reproduction of the class register from the community's final years lies on the dominie's desk. The last few entries list telling details in elegant copperplate handwriting: "Went to Glasgow" occurs frequently, while two children are marked simply as "died".
Life on St Kilda was tough in anyone's book, but Hirta was blighted by a terrible scourge, tetanus infantum, the "sickness of eight days", which between 1830 and 1891 alone wiped out 77 babies. Older children contracted it as well, ending their short lives wracked by terrible spasms. Some pointed to the local midwives' habit of daubing the umbilical chords of the newly born with the ubiquitous fulmar oil, but recent testing of soil samples from Hirta has shown that tetanus bacteria were, and remain, rife in the soil, partly because the islanders continuously recycled their own waste into the ground.
Tetanus apart, the islanders proved vulnerable to TB and other illnesses brought from the mainland, against which they had little immunity.
As men quit the unforgiving island life for the mainland, fewer birds were caught to sustain those who remained, and they became increasingly dependent on passing trawlers to supplement their winter diet. In 1928 the visiting police constable from Harris reported that the community was in its death throes. Two years later, with the help of the resident nurse, the 36 remaining islanders petitioned the government, but officialdom proved slow to respond. When a pair of civil servants finally paid a visit to Hirta, they were shocked at what they found and the evacuation went ahead.
All of which seems very distant as we perch on the cliffs above the village. Despite our fears, glowing sunshine is shifting fleetingly over the great scoop of the valley, the stone sheep pens and drystane dykes looking as inscrutable as those mysterious Nazca Lines etched across the Peruvian desert.
In the giddying void below, fulmars slide along the updraught in their hundreds, white flecks against the sluggish blue sea. Offshore, the fearsome black brow of Boreray is emerging reluctantly from its sheath of white cloud - Moby Dick in negative. Orca is waiting in the bay to take us out there.
Before we board her, however, as we sit beside the twisted prop of one of three aircraft which crashed there during the war years, we witness an aerial drama of another kind as two bonxies or great skuas pursue a hapless snipe overhead, the big predators twisting and turning on the little bird's tail like dogfighting Spitfires.
Orca transports us the few miles to the outlying stacks that play host to the world's largest gannet colony. Stac Lee towers above us like a giant, serrated shark tooth, Boreray vanishing into its lid of cloud.
The air seethes with wheeling gannets, their rakish, aerodynamic shapes graduating into the mist. As the bickering of countless birds drifts down to us we feel like intruders, as if we shouldn't really be here.
Perhaps that is what the St Kildans felt, but they still managed to hold on for 2,000 years.
Fact file: St Kilda
How to get there
British Airways/Loganair flights from Edinburgh to Stornoway start from 88. For more information see www.britishairways.com
Car Hire: A Fiat Punto hired for three days from Stornoway Car Hire costs 84, including VAT.
Caledonian MacBrayne offers a five-day saver ferry fare of 120 per car, plus 24.65 per person, Ullapool to Stornoway. www.calmac.co.uk
Where to stay
Jim Gilchrist stayed at New Haven B&B on the Isle of Scalpay, Harris (01859 540325). Further information from VisitScotland, tel: 0845 2255121; www.visitscotland.com
and there's more
Day trips to St Kilda from Leverburgh, Harris, cost 80 per person, weather permitting, and allow several hours on Hirta. For details, tel: 01859 502060; www.kildacruises.com
For information about St Kilda, visit www.kilda.org.uk
Scotsman Reader Holidays offer escorted holidays to a variety of islands including Barra, Skye, Rum, Mull, Harris and Lewis.
For more information call 0131 620 8400 or visit our website www.holidays.scotsman.com