The wooden fort, covering around an acre on Jamestown island, burned down in 1608 and historians had long presumed that all traces of it were washed away. Now a team from the Association for the Preservation of Virginia Antiquities has found on a site abutting the James river the clear imprint of a corner bastion, and of a section of palisade wall beneath a 17th- century church erected inside the larger fort which replaced the one built in 1607.
Along with evidence of the structure, the two-year search has uncovered a trove of period artefacts, including a soldier's helmet and breastplate, English coins from 1560 to 1603, clay pipes, Indian jewellery, a book clasp and a large number of arrowheads and musketballs.
Most dramatic of all was the recovery of a skeleton of a white male, estimated to have been some 25 years of age, who probably died of a musket wound. A musketball was found embedded in one of his legs.
"This is like a time capsule," said Dr William Kelso, the association's director of archaeology. "Jamestown didn't become a modern city on the same site, which would have obliterated it."
The first permanent English settlement in North America, Jamestown was the capital of the colony of Virginia until 1699. Today it is part of a national historic park comprising the restored colonial town of Williamsburg, a few miles inland, and Yorktown, where General Cornwallis came to grief in October 1781.
Today, the area is one of the most visited tourist sites in the country. But nearly 400 years ago Jamestown was a harsh and brutal land. Of the 104 people who survived the five-month Atlantic crossing and came ashore on 13 May, 1607, only 38 made it through the first eight months, the rest died of disease, starvation and skirmishes with the local Indians.
One at least of those skirmishes has passed from history into legend. Among the commanders of the original fort was Captain John Smith, who on a foray for food in December 1607 was captured by the local Indian chieftain Powatan and, by Smith's account, was only saved from execution by Powatan's daughter Pocahontas - a story very loosely related in last year's Walt Disney feature cartoon.
Indisputably, Jamestown was the cradle of English civilisation in the Americas. A first attempt at a permanent settlement, by Sir Walter Raleigh at Roanoke in what is now North Carolina, was abandoned in 1584. It was not until 1620 that the Mayflower put down anchor at Plymouth, Massachusetts.
At a ceremony yesterday George Allen, the Governor of Virginia, called Jamestown, site of the first-elected assembly in North America, "the source spring of American democracy".
From the island, Dr Kelso said, "evolved our political institutions, our language, our commerce and much of our culture. No other American site predates Jamestown in historical significance."
And, the archaeologists hope, they will soon find out far more. The present dig which began in 1994 is part of preparations for the fourth centennial of the Jamestown landing. Thus far, only $700,000 (pounds 460,000) has been spent on the $17m project. By 2002, if all goes well, not only will any lingering doubts about the authenticity of the find have been banished, but the secrets of the later "James Towne" site next to the replacement fort will have been unlocked too.Reuse content