I know almost nothing about Corneille de Lyon. I don’t have any books on him. I’ve never seen an exhibition devoted to him. But in museums across America and Europe, I find myself hovering, like a hummingbird poised to strike, in front of tiny portraits with green or blue backgrounds. And I frequently find, when I peer at the wall label, that they have been attributed to Corneille de Lyon.
None of them is signed. Although the paintings…