You may have scratched your head at the part in What Happens in the Ballroom about the Jack in the Green. It’s not as commonly known a May Day custom as the maypole, for example, but it does play a part in the festivities. Primarily for chimney sweeps, it was part of the usual May Day processions: The sweeps dressed up like bushes or trees (!!) and danced (or staggered, depending on their degree of drunkenness) down the street. Apparently, May Day was sometimes called Chimney Sweepers’ Day. I have no idea why. But here’s a fun picture of a Jack-in-the-Green and his drunken companions (colorized by the print owner).
