Now that we have the Great Stemma published online, it's a good time to consider what sort of commonalities it has with the "arbor juris" diagrams in Isidore's
Etymologies and with the
Peutinger Map. The most important observation is that all three are in a sense calques of the board game, where the meaning arises from traversing through the diagram, much as you jump a counter over the squares or circles of a board towards a goal.
As an
itinerarium, Peutinger is all about paths and distances, and not at all about spatial arrangements. One might argue that this is an adaptation to fit its roll form, but I wonder if this isn't a kind of deliberate elaboration from what would be needed for a mere map into something more sophisticated. As it happens, today's IHT edition of the New York Times
reports on an ingenious
new way of representing cities that overlaps a perspective view into a bird's eye view. It was designed by London's
Berg studio and is an exhibit at the NY
Museum of Modern Art. The Peutinger Map may not be a broken or primitive map, but instead a highly sophisticated meta-map like the Berg one (I won't comment here on the Richard
Talbert proposal that the map is more show-off than practical).
One could argue that the common feature of Peutinger, the arbor iuris, the Great Stemma and also items such as the arbor porphyriana is the invitation to the reader to discover and explore paths, usually crooked paths. That is what the fila and the hypothetical timeline of the Great Stemma are about. The open question is about how accurately the fila and timeline were aligned with one another.
One important ancillary point, to my mind, is that our knowledge of all these graphic schemes is diminished by the difficulty that every scribe, whether Antique or medieval, must have had in accurately copying technical drawings by hand. Last year, I
copied the triangular version of the "arbor iuris" and found it a very tricky task, even with good graphics software to help me.
Practice at copying these ingenious graphics has been helpful in understanding their transmission. When I am looking at a poor copy of a drawing, I now assume that its predecessor was more observant of the regularities generally. The more accurate predecessors of these drawings might have had a lot more fine-scale axial information, which is the easiest feature to get out of alignment, as we also seen in the Eusebian
Chronological Canons.
But we cannot even begin to reverse this degradation unless we know what equipment such a copyist used when reproducing such drawings, and there I am afraid I have not read enough research. My understanding is that desks were uncommon: according to
Kurt Weitzmann, texts were commonly copied onto papyrus rolls by a scribe sitting tailor-style, wearing a tight skirt as the support for his papyrus, which was laid obliquely over the left knee. In the early codex period, the folios were also inscribed on two knees (at least that is true of the Spanish monastery depicted in one of the Beatus codices). It seems to me that big graphics like the Great Stemma could not be competently copied that way, especially if straight axes had to be preserved. I have not studied how paintings were reproduced, but would guess that this done on tables or easels, since the artist had to be at some distance from his canvas to wield his brush.
When we consider how a pen-drawing was copied, I can only speculate. My guess would be that this was a job for a specialist. A tracing through translucent "paper" of some nature? Hardly likely, as the customer would surely expect a product on a robust support. In the 19th century, technical draftsmen used technology such as pantagraphs, but I doubt if these were known in Late Antiquity.
Again, I am only guessing, but I would suppose that the most efficient method would be to stretch a net over the source, another net over the destination, and plot each square or hexagon from one to the other. If a non-specialist scribe were given the task, he might not have the equipment, or the training, or the wit, or the time to do this. If he were particularly incompetent, he would not even complete each panel left to right but might simply hurl squiggles on the page to represent his "overall impression" of the model, then fill the gaps. The Urgell Beatus version of the Great Stemma exemplifies that sort of chaotic, ill-planned copy. It is hardly surprising that we have rather little of the pen-drawings of Antiquity.
Now, I think this encourages us to contemplate the question of Antique "technical" drawing with more attention to the intelligence behind each drawing than to the deficiencies in execution of any of its copies (this was my criticism of Klapisch-Zuber). To some extent, we may be able to at least discover the right questions to ask by looking at collective memory, the practices in other periods, and even our own perceptions. The answers to those questions naturally depend on evidence, but we should try to connect to the intelligence or the intention of the Antique authors.