Because, Mark, he was sometimes on Northern ships(which had changed registry to Liverpool during the American Civil War in order to avoid the attention of Southern ships like the Alabama. In particular he was on the Yankee ship Levant (Liverpool reg.350303 of 1436 tons, built 1841) from 9/5/64 to 14/9/64. We've talked to men in Watchet who can remember, from when they were boys, talking to old Yankee Jack (he died in 1933) - how close is history!