Children’s book about French cathedral with gargoyl unable to bring the church due to its design

Hi, I had a book in NY in the early 1970s that was probably from the 1940s and the main point was to explain to children why the keystone in the pointed arches of a cathedral (I think Notre Dame) was so important by having the story be about how a particular gargoyle could not push down the pointed arches to the design due to the keystone (might have also explained flying buttresses). The gargoyle then live out the rest of his life atop the cathedral, disappointed at his lack of success. The book was in English, probably about 20 pages, I’d say written to about a 10 year old’s level and had line black-and-white drawings of the arches and the gargoyle able to bring down the ones with a more gentle, u-shaped curve but not the more pointed arches. The copy I had was hardback. Thanks for reading this!