Thank you all for your replies.
Michael was born abt 1843 & Betsy about 1840, & on one census the surname was Cohn. I wasn't sure if this was a mistake or a variation of Cohen.
I think I must do some background research on immigrants from Eastern Europe in the 19th century & on Poland's changing borders. It will help to add flesh to the bones of my tree.
Makes a change from ag. labs. in Kent!
Betty