The portion you quoted is a little misleading (understandably so for conciseness, but it does give the wrong impression). With a bit more context: "Orowan had

The portion you quoted is a little misleading (understandably so for conciseness, but it does give the wrong impression). With a bit more context: "Orowan had quipped that there might, indeed, be some truth to the story about glass flowing. Half of the pieces in a window are thicker at the bottom, he said, but, he added quickly, the other half are thicker at the top." Which reads to me as a joke. I note this simply because it seems sub-optimal to introduce myths about the thickness of glass in old cathedrals when correcting a myth about glass in old cathedrals :)