Hi Ray,
Pleased to get your reply. I see from the thread there is another "Jean" posting messages - very confusing! I have asked on the forum whether there is a way of getting in touch without publishing personal addresses - wait to find out. Otherwise will send you my email address. In my post of October I show how the Gick line enters the equation - mother of Christiana Davidson, wife of John Curphey of Cordeman was a Gick, born earlier at Cordeman. I have actually inherited some spoons with the G for Gick on them, which have come to me via the Newton connection (Isabella Curphey, daughter of John married Edward Newton).
In my jottings, I have noted that a Hugh Davidson, b. 22.4.1802 Downpatrick, married Isabella Gick, b. 29.11.1801 Cordeman. Could this be your "missing" Isabella who married Joseph Clarkson? Are the dates approximately correct?