SAN FRANCISCO (AP) - Previously hidden writings of the ancient Greek mathematician Archimedes are being uncovered with powerful X-ray beams nearly 800 years after a Christian monk scrubbed off the text and wrote over it with prayers. Over the past week, researchers at Stanford University's Linear Accelerator Center in Menlo Park have been using X-rays to decipher a fragile 10th century manuscript that contains the only copies of some of Archimedes' most important works. The X-rays, generated by a particle accelerator, cause tiny amounts of iron left by the original ink to glow without harming the delicate goatskin parchment. «We are gaining new insights into one of the founding fathers of Western science,» said William Noel, curator of manuscripts at Baltimore's Walters Art Museum, which organized the effort. «It is the most difficult imaging challenge on any medieval document because the book is in such terrible condition.» Following a successful trial run last year, Stanford researchers invited X-ray scientists, rare document collectors and classics scholars to take part in the 11-day project. It takes about 12 hours to scan one page using an X-ray beam about the size of a human hair, and researchers expect to decipher up to 15 pages that resisted modern imaging techniques. After each new page is decoded, it is posted online for the public to see. «We are focusing on the most difficult pages where the scholars haven't been able to read the texts,» said Uwe Bergmann, the Stanford physicist heading the project. Born in the 3rd century BC, Archimedes is one of ancient Greece's greatest mathematicians and discovered the principle of buoyancy while taking a bath.