Shirley, I just happened upon this site and was floored with all the work you and others have done -- it gives me a great deal more information that I would like to expand upon. My information stopped with the 1851 English Census and the household of Hugh (Montgomery) Boyd of County Antrim, whom I only knew was married to Mary.
I didn't know her maiden name, but it makes perfect sense for it to have been Adair, given that the son from whom my partner is descended is David Adair Boyd, married 15 May 1884 in Ferndale, CA to Grace Ann Bartlett (deceased 7 Jan 1921 in Eureka CA and buried 9 Jan 1921 in Myrtle Grove Cemetery in Eureka). While they also had a son by the name of David Adair Boyd, my partner is descended from their eldest child, Florence Ann. His father's name was Clement Adair (the first name coming from his father, Clement Roberts).
The son is the first one in the family to actually have the name Adair as a first name (I guess). I have much more information on the Bartlett branch of his family (as well as some of the Roberts branch), but very little on the Boyds and Adairs, and would welcome any information with respect to source material that would help me.