I find I've got another early copy, "Scew Ball" in Holloway and Black's 'Later English Broadside Ballads', #109, with many minor variations from that above. It looks like I was wrong in saying the last verse was a bit corrupted. It just strains one's credulity a bit to have Squire Mervin/ Merwin/Mirwin talking to Skew Ball's rider while the latter is in the middle of the race. But who says songs have to be logical?