"The beam is 10,000 times more intense than a conventional x-ray tube," such as the kind used at hospitals, Bergmann said.
The intensity allows the researchers to scan a page in about 12 hoursabout 300 times faster than using an x-ray tube would allow.
The beam touches each spot for less than three milliseconds, keeping radiation exposure far below levels that could damage the parchment, Bergmann says.
Scientists had already reconstructed most of the text from the manuscript using multispectral imaging. This techniquedeveloped for NASA satellite surveys such as Landsat programoverlays images taken at different wavelengths of light, from infrared to visible to ultraviolet.
But up to 20 percent of the text remained inaccessible until Bergmann and his colleague Robert Morton proposed using x-ray fluorescence.
Lost and Found
Like most other remaining texts of antiquity, the works of Archimedes survive only thanks to scribes who kept copying them on parchment throughout the Middle Ages.
But parchment was often recycled by "palimpsesting," a blunt washing procedure that left little, if any, of the old text.
In 1906 Danish classicist Johan Ludvig Heiberg discovered a 13th-century prayer book in a library in Constantinople (now Istanbul, Turkey). That book became known as the Archimedes Palimpsest.
Barely readable under the prayers was an older texta tenth-century copy of ancient Greek texts. Heiberg recognized, painstakingly transcribed, and translated parts of seven works by Archimedes, two of which would have otherwise been lost.
Later, the Palimpsest disappeared, presumably stolen during the collapse of the Ottoman Empire. Badly damaged by mold and fire, it resurfaced at a New York auction in 1998.
Fake medieval paintings now completely covered four of its pages.
An anonymous collector bought it for two million U.S. dollars, entrusting it to the care of the Walters Art Museum in Baltimore, Maryland. The collector has since funded the book's restoration and analysis.
Nigel Wilson, a historian at the University of Oxford in England, says the same technologies used on the Archimedes Palimpsest could shed new light on a number of other palimpsests conserved in libraries around the world.
"There are going to be plenty," Wilson said. A text recently discovered in the Vatican Library, for example, contains previously unknown fragments by the ancient Greek playwright Menander.
It may be some time before historians are able to assess the full importance of the new pages.
Meanwhile, Bergmann's team is performing a third round of imaging, which will end August 7. Slated for scanning are the four painted-over pages.
Free Email News Updates
Best Online Newsletter, 2006 Codie Awards
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
SOURCES AND RELATED WEB SITES