Ptolemy's hidden Greek text deciphered after 200 years

Researchers have decoded an ancient manuscript they believe was written in the first century A.D. by the Greek-born Egyptian mathematician and astronomer Claudius Ptolemy.

The manuscript was originally unearthed in 1819 by Angelo Mai, a Roman Catholic cardinal and expert in ancient literature, who found it concealed in a library at Bobbio Abbey in northern Italy. It was written on parchment in Greek, according to LiveScience

Previously, specialists had difficulty translating the manuscript and could only translate sections of the text. In the sixth or seventh century A.D., someone reused the pages and printed another work — in this case, Spanish theologian Isidore of Seville's "Etymologiae" — on top of Ptolemy's writing, since parchment, or prepared animal skin, was thought to be astronomically expensive.

Someone "cleaned" the study
The examination also found that someone had "cleaned" the study in an effort to read it, turning some of the pages a dark brown.

"Angelo Mai had splashed chemicals on the pages to erase the Latin," study co-author Alexander Jones, a professor at NYU's Institute for the Study of the Ancient World, told Live Science. "On some pages, [he] did a pretty good job of erasing the writing. And then you also have this other writing written directly on top of Ptolemy's."

"The basic idea is that different wavelengths of light have different illuminations on a page that's written using ink of any particular composition," Jones said.

"The technique is to take lots of digital photos with different wavelengths of light and then combine these images by adding and subtracting the signals of various proportions to see if you can bring out the writing you want to see and suppress the writing you don't. For each page, it's a different recipe," he added.

Particularly noteworthy was the discovery of a handbook by Ptolemy that described how to build a meter scope, an armillary instrument used to measure distances and observe the stars. The tool, which is made up of nine pivoting metal rings, might be used to help someone find their bearings while performing astronomical computations. The investigation found that in the book, Ptolemy recommended building an instrument with a maximum diameter of roughly 1 foot (0.3 meters).