Six years of living in the US only increased my bafflement at why it should celebrate its supreme national holiday on a day when 90 per cent of the country is a sauna. Not, however, Nantucket, where serious humidity simply doesn't happen. Most people have vaguely heard the name - possibly because of whales (of which more in a moment), more probably as an aid in composing limericks. But those who have been there are enchanted for life. On the map, it's just a small island 30-odd miles south of Cape Cod. But when the mist rolls in, or the wind starts to blow, haunted, mysterious Nantucket turns into another world. Fog in Nantucket Sound, continent cut off, a chauvinistic islander might say. Except the severed party is Nantucket, in fair weather as well as foul.
All of which makes the getting there even more pleasurable. These days, of course, in summer you can fly in from Boston or New York to the spanking new little airport, its terminal clad in the clapboard obligatory for schools, supermarkets and every other modern building on Nantucket. But islands should be approached by the sea. From Boston, it's an hour-and- a-half's drive south to Hyannis and the ferry. Hyannis itself is a Kennedy theme park, wall-to-wall Camelot in its quaint stores, and cheek-by-jowl Irish bars on Main Street. But, on the boat, Kennedy-spotting gets serious, as you glide past Hyannisport and the family compound away onshore to the left.
The other route is from the south. As if by miracle the climate changes 50 to 100 miles north of New York; suddenly, you're out of the sauna and into New England. The towns are called New Haven, New London and, finally, New Bedford, forlorn victim of the collapse of North Atlantic fish stocks. Nearby is Fall River, where, in 1892, Lizzie Borden may or may not have committed the 19th century's most famous double parenticide. The house where the murders happened is now a bed and breakfast.
The two-and-a-half-hour journey across the sound is magical. When the fog banks roll in, only ships' horns break the feathery silence. On a clear day, there is a sensational moment when, as the diminishing mainland finally disappears, you pick out the first pencil line on the horizon ahead. Then a white water tower appears, then a lighthouse, followed by tiny dots for houses and, finally, the harbour. And so, welcome to a genuine American time-warp.
Politics is the daughter of history, they say, and history the daughter of geography. And nowhere more so than Nantucket. The Coffins, who were Quakers, were seeking respite from the rigid Puritanism entrenched on the mainland. Then came the whalers. Between 1740 and 1840, if whale oil was the petroleum of its day, then Nantucket was its Saudi Arabia. But King Coal took over, and Nantucket abruptly reverted once more to forgotten fishing port, the mansions of its great whale captains the sole reminders of its former splendour.
In winter, the place is bleak and raw. In summer, though, when the population quintuples to 40,000, Nantucket is reborn. But outside the very centre of town, the tourist crowd does not madden. Nowhere is higher than 90 feet above sea level. Most of the island is heath, bog, moorland and dwarf forest, scoured by the constant winds. Only in sheltered areas to the north and east do you find real woodland, and even there, the main crop is cranberry. But nowhere on earth offers the same communion with the sea.
Thanks to the Gulf Stream, it is usually warm. Beyond that, however, anything is possible. Depending on the weather and the time of day, the colour ranges from slate grey or sandy brown to green, turquoise blue or shimmering gold. On the sheltered north coast, the waters are shallow and gentle. Jetties Beach is a children's paradise of soft sand, seashells, shrimps and scuttling crabs. Just beyond, lies bigger game. Take the $20 lobster boat trip, where they pull up a dozen or so pots each day. Expensive? Only if you don't like the fresh-caught lobster you're likely to be given at the end of it. But the southern shore - next stop Ascension island - is another matter. In summer, the clifftop walks are scented with dog rose. Below, are broad, gale-swept beaches. The breakers are wild, the surf huge and the sunset's like the last judgement.
And so to the whales. In July and August, you can take whale-watching trips and, most times, spot the beast. If not, there is always the Nantucket Whaling Museum at the bottom of Broad Street, chronicling one of the most dangerous, gruelling and foul-smelling trades devised by humankind. Its every facet is on display: boats, harpoons, maps, diaries and artefacts from epic voyages that could last three years, as well as scrimshaw, intricate carvings on whale teeth, on which seamen used to while away the empty weeks. There, too, you will learn of the "Nantucket Sleighride", the terrifying experience of being dragged in a small boat by a harpooned sperm whale. Afterwards, wander up to the houses above the harbour, each with its rooftop crows' nests where wives once watched anxiously for the boats to come in. Herman Melville devoted a chapter of Moby Dick to Nantucket, and steel- willed is the visitor who resists buying a book he will almost certainly never read.
Now, tourists have brought new wealth to Nantucket. Be warned, it is expensive. This preserve of affluent middle-class East Coasters is not for backpackers. There are bed and breakfasts, but best of all is to rent a house - except the ones on the beach or cliff: $2,000 and upward a week in high season. Forget about bringing a car ($180 round trip on the ferry and summer bookings must be made by February). Leave it at Hyannis, pay $11 for the crossing, then rent a bike for $70 a week. Measuring 10 miles by three, at most, and without a hill worth the name, Nantucket is perfect for the cyclist. Beware, too, genteel ladies running cute shops selling scrimshaw and wicker lightship baskets at prices to make a whale captain weep.
But the fresh fish is wonderful - and so is the Fourth of July: festivities organised by the Nantucket fire-brigade on Main Street by day, and fireworks on Jetties Beach in the evening. So what if you have to take a windcheater and a few blankets? And go soon, for Nantucket is disappearing. Each storm tears away another chunk of sand and dune. In 2,000 years' time, scientists calculate, there'll be nothing left at all.
How to get there
In July, Boston will served by eight flights a day from London, on American Airlines, British Airways and Virgin Atlantic. But they will be busy - book your flight now. The ferry from Hyannis is a 90-minute drive from Boston; you can also fly from Boston.