The Colosseum Was a Skydome?

This is one of those archeological stories that, if I were to follow the sage example of David Nishimura at Cronaca (David's recent post on the military occupation of the 9th-century minaret of the Great Mosque at Samarra is just one of the excellent reasons you should be reading his blog), I should present with a grain of salt. An article (A l'ombre du Colisée, February 5) by Philippe Motta for Le Figaro reports on theories put forward by an engineer in Toulouse, who claims to have uncovered precisely how the Romans covered their arenas. Based on narrative accounts and mosaic images, it seems likely that the Romans actually did use large fabrics (velaria) to cover arenas and amphitheaters, so that spectators could sit in the shade of these sunshades hung over the tribunes. How that might have been done, without blocking the view in the higher seats, is the question (my translation):

Trained at Arts et Métiers [the Ecole Nationale Supérieure d'Arts et Métiers], and after having worked in the automobile and aeronautical fields, René Chambon is now retired, but his curiosity remains active. So, after watching a television show on the subject, he learned that the enigma of how veils were deployed persisted for two millennia after the last applause had died down in the Empire's arenas. "I found the question fascinating," he says.

The Colosseum in Rome would be his example, his starting point, the base of his calculations: René Chambon visited, read about, and learned everything about the emblematic theater, "as high as a building of about 15 stories, able to contain more than 50,000 spectators." At the same time and for the purpose of comparison, he did not neglect anything he could discover about other similar structures of the period. He documented narratives and rare images and became convinced that the covering of arenas was accomplished "with a simple system, capable of resisting wind but supple enough to be deployed and taken down quickly and by human power, since there is no evidence indicating the existence of machinery."

On the basis of force calculations, this engineer, who helped realize the first simulators for astronauts, went to work on these theories. He quickly abandoned "the stubborn but unrealistic idea" of horizontal beams on which swaths of cloth could have been suspended. On the other hand, he noted that on the Colosseum, as on many other theaters, there were at the summit "remains of consoles that could have supported masts," which would have been placed vertically, extending above the façade. He took advantage of this possibility. Combining the situation at the site with calculations, he put together this technical theory: placed on the arena floor, a ring of cords bound to a set of lines "like a spider web," could have been raised up to the top of the building. To serve as a roof, it would be enough that the network of cords be sufficiently in tension to support the weight of a tent covering.

After ten months of research, like a true engineer, Chambon put together a model of the Colosseum with a version of his theoretical covering. A certification agency, Bureau Veritas, is vetting the research and calculations. Academic specialists will surely have something to say about the theory, but that may take a while. In the meantime, Chambon intends to reproduce the system to create similar temporary coverings for use in temporary hospitals, for example, in humanitarian interventions. The original article in Le Figaro is now archived, but there is also this article (Le rêveur des arènes, February 1), also by Philippe Motta, from sudouest.com, which is almost identical to it.