Skip links

Correlation Is Not Causation, Iron Framing Edition

I’ve mentioned the Rookery in passing a few times. It’s a fantastic 1886 office building in Chicago and holds a place in any history of early skyscrapers. It’s not a skeleton-frame building and actually contains a number of masonry bearing walls, but, as I discuss in The Structure of Skyscrapers, having an old-fashioned structural form is not an impediment to being a skyscraper. In any case, the upper office floors are a square donut in plan, arranged around a central courtyard. The base of the courtyard is a skylight over the lobby, which is arguably the best thing about the building. That’s a historic view of the lobby above; the one below is from the 1967 HABS survey, during the (literally) dark era when the skylight was painted out. It ash since been restored.

So far, so good, but time to throw an 1863 monkey wrench into the works. Here is a hypothetical iron-framed roof for a concert hall by Viollet-le-Duc, from volume 2 of Entretiens sur l’architecture:

They’re not exactly the same, of course, but there is a strong familial resemblance. Viollet-le-Duc’s book was well known among architects, so I can come up with a number of possible explanations:

  • Complete coincidence. Burnham & Root and Viollet-le-Duc were solving the same problem – spanning a large open area with iron framing – and came up with similar solutions.
  • Complete non-coincidence. Someone at B&R saw the book illustration and said “let’s build one of those.”
  • The zeitgeist. Architects and engineers spent a lot of time in the pursuit of ideal forms for designs with the new structural materials of (in chronological order) cast iron, wrought iron, and steel. Neither the designers at B&R nor V-l-D were operating in a vacuum and therefore all would have been aware of the on-going discussion.
  • Technological determinism. This is simply the best possible form for a roof designed with the materials of the nineteenth century so it was inevitable that skilled designers would end up with it.

I’m sure there are others. It may come as the opposite of a shock to hear that I have strong opinions about the likelihood of these options. Starting with the easiest: technological determinism is a terrible concept in general and flat-out wrong in this case. There are plenty of ways to use wrought and cast iron to span a large space with a roof. Coincidence is possible but unlikely, since it requires both B&R and V-l-D to be design naifs, unaware of the discussion going on about the topic. I think the zeitgeist is the most probable explanation simply because this kind of thing happens frequently. When an idea is being kicked around in the architectural community, variations on it have a tendency to crop up all over. Sometime the originator of the idea is clear, sometime not.

Finally, Burnham & Root were talented architects who ran an office full talented architects. They had no need to steal ideas. But that’s not proof that they didn’t and, barring the discovery of some unknown and amazingly specific letters or diary entries, we’ll never know if they did.