British researchers think they have solved the decades-old mystery of why ancient Britons transported massive rocks 250 miles from Wales to Salisbury Plain to construct the enigmatic Stonehenge monument: They believed that the stones possessed healing powers.

British researchers think they have solved the decades-old mystery of why ancient Britons transported massive rocks 250 miles from Wales to Salisbury Plain to construct the enigmatic Stonehenge monument: They believed that the stones possessed healing powers.

A variety of archaeological evidence, including results from the first excavation inside the monument in nearly half a century, also suggest that the first stones were placed at least 200 years later than previously believed and that the Romans might have altered the stones during their occupation of Britain.

The findings do not conflict with other recent theories about the uses of Stonehenge — which indicate that it was an astronomical observatory, a cemetery and the site of biannual celebrations that honored the dead and the living. But they do suggest that the monument was also an ancient Lourdes where pilgrims congregated to have their wounds and illnesses magically repaired.

Stonehenge has "multiple meanings and multiple uses" that might have changed over the centuries, said archaeologist Mary Ann Owoc of Mercyhurst College in Erie, Pa., who was not involved in the new research. "To limit it to one is an error."

The idea that the stones are not just building materials but have some efficacy "is tremendously appealing as an idea," said archaeologist Julian Thomas of Manchester University, who also was not involved in the research. "The idea that they were brought there because they have some kind of power seems to me entirely plausible. But whether it is just about healing is another question."

The new findings were reported in the current issue of Smithsonian magazine.

The monument comprises concentric circles of massive stones, some weighing as much as 50 tons, surrounded by a circular earthen bank and ditch. The largest stones, called sarsens, were quarried about 24 miles north of Stonehenge at Marlboro Downs. The smaller ones, called bluestones because they take on a bluish cast when wet or cut, were imported from Wales at great effort and expense.

Medieval literature and folklore associate healing properties with the bluestones, but researchers have assumed that this was a recent association unrelated to the monument's initial purpose.

But archaeologists Timothy Darvill of Bournemouth University and Geoffrey Wainwright, president of the Society of Antiquaries in London, speculated that the tradition had its origin much earlier.

To investigate, they first surveyed the Preseli Mountains in South West Wales, site of the quarry known as Carn Menyn, source of the bluestones. They found that many springs around the quarry had been dammed up to create "enhanced springheads," pools of water that the sick could bathe in.

That idea was supported by prehistoric art and burial cairns associated with the pools, created by the same early Britons that built Stonehenge. When they saw these, Wainwright recalled, "Tim and I looked at each other and said, 'It's got to be about healing.' "

In April, the team excavated an 11-foot-long trench on the inner circle of the bluestones at Stonehenge, the first excavation at the site since 1964. The site is such a cultural monument that permission for the work had to be obtained from the British Cabinet. And for the first time at the site, workers used water flotation to isolate small fragments of carbonized plant material that could be used for dating.

Fragments from the bottom of the trench indicated that activities were occurring at the site from 7330 to 7070 B.C., much earlier than had been suspected. The orientation of the materials in the soil suggest that they were associated with human activity, but it is not clear what people were doing, Darvill said.

Carbon fragments at the base of the bluestones indicated that they had been set into the soil sometime between 2400 and 2200 B.C., two to four centuries later than the previous date of 2600 B.C. "That fits rather nicely with the spread of Beaker Culture pottery across Europe," which was associated with large-scale population migrations, Darvill said.

That date also is contemporaneous with the grave of the so-called Amesbury Archer, an adult male excavated nearby with a healed head wound and a damaged left leg. Darvill and Wainwright speculate that he and other injured people buried in the area came there to seek the healing powers of the stones.

More recent layers of the strata showed fragments that were chipped off the bluestones and at least two Roman coins from well below the surface. Clearly, Darvill said, populations have been chipping away at the bluestones for long periods and taking them away as talismans and lucky charms, indicating that the stones' reputation for healing powers extends well beyond medieval times.