ISAW Director Alexander Jones Collaborates to Reveal Lost Astronomical Treatise by Claudius Ptolemy

By Lily Wichert

Alexander Jones – ISAW Director and Professor of the History of the Exact Sciences in Antiquity – collaborated with researchers at the Sorbonne to reveal ancient Greek scientific texts in an ancient palimpsest manuscript. Jones was recently interviewed by two web magazines about his contributions to the project: "Ptolemy's Lost Manuscript Discovered" in Newsweek and "Hundreds of years after" in Ars Technica.

A book written in ancient Greek by the astronomer Claudius Ptolemy that was thought to be lost has been rediscovered thanks to multispectral imaging and to its decipherment and interpretation by Victor Gysembergh and Emanuel Zingg at the Centre Léon Robin (Sorbonne University, Paris) and Alexander Jones at the Institute for the Study of the Ancient World (New York University). Dating from the mid 2nd century CE, this treatise turns out to constitute the earliest known text entirely devoted to describing a scientific instrument. The first results of the research team were published on March 9, 2023 in an open-access paper in the journal, Archive for History of Exact Sciences. 

In a fruitful partnership of the humanities and natural sciences, the decipherment was made possible though the production of multispectral images. The imaging was carried out in the first place by the French company Lumière Technology, and subsequently by an international team from the Early Manuscripts Electronic Library, the Lazarus Project (University of Rochester), and MegaVision Inc.

The unique manuscript preserving the new treatise by Ptolemy is a palimpsest (a manuscript containing parchment pages recycled from an earlier manuscript, so that faint traces of the texts in the earlier manuscript underly the text written in the present manuscript) that is now kept in the Veneranda Biblioteca Ambrosiana, Milan (Italy). It is known to have originated in the library of the Abbey of Bobbio, one of the most important collections of manuscripts in Italy at the beginning of the Middle Ages, and an inspiration for Umberto Eco's novel The Name of the Rose. Twenty-four pages of the manuscript are written on parchment sheets that came from a Greek manuscript of the 6th or 7th century that contained a number of writings by Claudius Ptolemy, the most important Greek astronomer of the time of the Roman Empire. These sheets were partially erased in the 8th century and reused for a Latin text, the Etymologies of Isidore of Seville. The palimpsest pages were noticed in the early 19th century but have largely resisted efforts of scholars to read the Greek texts for two hundred years. 

The new text, which is not completely preserved, describes the manufacture, assembly, and uses of an instrument composed of nine interlocked and nested metal rings that can be manipulated so that they represent various imaginary circles involved in astronomical observations and calculations. Despite the loss of the book's first and last pages, which would have given the author and title, it has been possible to identify the instrument as one that Ptolemy was known to have invented and called "Meteoroscope" ("Celestial Viewer") and also to identify the book as Ptolemy's own treatise on the subject, which is mentioned in certain texts from antiquity but had been thought to be lost. This is a major discovery that will shine new light on the history of ancient astronomy and scientific instrumentation.

Image depicting ancient astronomer Claudius Ptolemy. Greek mathematician, astronomer, and geographer Claudius Ptolemy wrote manuscript dedicated to his astronomical invention, the Meteoroscope