The mysterious circle of stones that rises on Salisbury Plain near here has stood as a marvel for thousands of years, its origins and purpose shrouded in the mists of history. But a just-completed excavation of Stonehenge, the first within the ancient circle in more than 40 years, could provide some of the first reliable explanations for one of the greatest wonders of the prehistoric world. A team of British archeologists hopes to prove its theory that nearly 4,000 years ago Stonehenge was regarded not as a place of sacrament for the dead, but as a temple with unique healing powers. The dig is investigating about 82 bluestones - a double circle of rocks, some weighing as much as 4 tons, that were brought in during the second stage of Stonehenge, which began about 2150 B.C. and account for the first stone construction at the site. About 150 years later, these were rearranged and surrounded by the much larger sarsen stones that have become iconic of Stonehenge. Yet it is the bluestones, somehow hauled to the Salisbury Plain from the Preseli Hills in Pembrokeshire, Wales, that researchers say hold the key to the mystery of Stonehenge. Although the researchers found to their dismay that the area they examined had been tampered with in Roman times, they still hope the excavations will help show that the bluestones were once viewed as therapeutic. Over the years, Stonehenge's legends have been many. Some said the devil bought the stones from a woman in Ireland; another story suggests they were placed on the plain by the wizard Merlin; others have sworn that aliens built the monument and left it as a place for worship, or that Druids built it as a temple for sacrificial ceremonies."You could put 10 archeologists in a room, and you'd get at least 11 theories," said Dr. Andrew Fitzpatrick of Wessex Archaeology, a private company involved in the excavation, which was approved by English Heritage, which manages Stonehenge.