Reading Between the Lines: unearthing structure in Ptolemy’s Geography

Leif Isaksen (Southampton)

Digital Classicist and Institute of Classical Studies Seminar 2010

Friday June 4th at 16:30, in room STB9, Senate House, Malet Street, London WC1E 7HU

Ptolemy’s Geography is generally seen as the high-watermark of ancient cartography and its apparent rediscovery in 1295 had an impact on contemporary mapmakers that remains to this day. Yet ever since it became broadly available, scholars have noted that it is troublingly inconsistent both internally and with the environment in which it was supposedly compiled. We wish to propose new techniques by which this long-standing problem in the history of mapping can be approached.

The manuscript tradition is complex but three principal components in the extant works are known: Book I, a theoretical introduction to map-making; Books II-VII, principally a catalogue of locality coordinates; Book VIII, comprising a series of maps along with descriptions. The introduction does not refer to the later books and the latter two sections are inconsistent with each other both in details and the conventions they use. Bagrow (1945) argued that neither the catalogue nor the maps were Ptolemaic, particularly on the basis that some localities referred to could not predate the 11th century. As recently as 2009 however, Mittenhuber has argued that even the map tradition can be traced back to Antiquity. The logic that permits such diverse opinions to co-exist is the general acceptance that both the catalogue and the maps have been corrupted, amended and embellished throughout their history. The heavy weight placed on minor differences between manuscripts or oblique classical allusions to the text make arguments about the origins of the Geography hard to validate. It is therefore imperative to find more robust means to look for structural trends. The recent digital publication of the coordinates (Stückelberger and Grasshof 2006) provides a variety of new possibilities. We are not alone in advocating computational procedures (see e.g. Livieratos et al. 2008) but propose two techniques that do not appear to have been considered in the literature so far.

First, statistical analysis of the coordinates assigned to localities demonstrates clearly that ostensible precision (whether to the nearest 1/12, 1/6, 1/4, 1/3 or 1/2 degree) varies considerably by region and is locally heterogeneous. In other words, the composite nature of the data cannot only be confirmed, but we can build a clearer picture of how the sources may have varied by area. Secondly, while many studies have addressed either the point data or the finished maps, simple line interpolation between coordinates following the catalogue provides a unique insight into the ‘invisible hand’ of the author(s). The unmistakable stylistic families that emerge, and the ocassionally arbitrary limits imposed on them, again provide important evidence about the catalogue’s internal structure. The application of these methods is very much a work in progress but we hope to demonstrate that even a cursory examination of the results provides new insights into the development of a text that changed the world.


The seminar will be followed by wine and refreshments.

Audio recording of seminar (MP3)

Presentation (PDF)